MXMC_ENGINEERING

I took Miles by Motorcycle live on HipHopVM on December 15th.

I was concerned about crash problems since it's a long lived process so I set it up to be monitored by ?upstartd, which will restart the thing automatically if it crashes. However, it's been remarkably trouble free.

It simply works.

I was playing with Google's Webmaster tools a bit when I came across this interesting graphic showing crawler page download times for the last few months:

It's pretty obvious when the site was switched over to hhvm. :)

Simply fantastic.

My intention with my my "Adventures in Configuring HipHopVM" article was to describe my experiences in the hopes that it might be useful for someone else who's trying to get hhvm running. Maybe I could save someone else some time and headache. I didn't do any rigorous performance benchmarking but I did post the observation that one one particularly slow page I have, which was loading in something around 5 seconds on my development machine under PHP, would load in around 0.6 under HHVM. HHVM is wickedly fast but I didn't think much about it because it wasn't what I was focusing on. I was just happy my code was running on HHVM at all.

Imagine my surprise when the article was shared out by the HipHopVM Facebook page. From there it found it's way to Reddit. Then an article was written about it on the HighScalability blog. A number seemed to latch on to the speed observation.

They say you should never read the comments because only pain and darkness awaits you there. But I did not heed this sage warning and went obsessively reading all comments I could find. My world darkened and I began to despair.

One comment posted to the HighScalability blog article stuck with me:

"How does it compare to a modern php (5.4, 5.5) best-practice implementation? This seems a very roundabout way to improve performance, verging on architecture astronautics, unless he is trying to get a job at facebook. ... We have to take his word for everything."

This got me thinking. While the focus on the article was on getting it working with a non-trivial codebase, he does have a point that there's no way to independently verify the result since my code is not opensource yet, and may never be.

My platform is a mix of SQL, noSQL on top of MySQL (akin to the way FriendFeed implemented a NoSQL layer), tons of classes, a custom XML domain specific language parser, expression evaluator and a lot of I/O. As such it has many external dependencies that are greatly affected by configuration changes and what else is happening on the machine. What it does not do is strictly isolate the core PHP language itself so that one can make a clear apples to apples comparison between PHP and HHVM language implementations. We could do something similar to compare the full stack but that would then involve comparing the HipHopVM stack to other components such as Apache.

Interestingly the commentor went on to state that "modern php is not slow".

In computing as in motorcycling, if you have never gone fast then slow may seem fast. PHP is an interpreter. Of course it's slow.

As a general rule, I don't believe in benchmarks. They give you little insight into how a given thing is going to perform in your use case. I can tell you, subjectively, across everything I have run through it, HHVM is "way faster" than PHP ranging from 2X to 9X faster depending on the situation. For most scenarios I've tried it seems to sit somewhere between 2X and 3X faster.

I don't specialize in benchmarking but I have spent some time trying to think of a real world problem one could use as a fairly decent benchmark that would have a few qualities:

• it would be something useful.
• it would test the speed of the core language without involving extensions and it would not be I/O bound.
• it would clearly demonstrate how hhvm can allow PHP to be used in problem domains where it currently makes no sense to do so.
• it would be something that can be independently verified.

PHP Notice: Uninitialized string offset: 21 in ppage/examples/expressionLanguage/ELLexer.o.inc.php on line 401

$startTime = microtime(true); $counter = 0; while ( $counter++ < 1000 )     {     $i = 0;     $call = new ELCallBack(); foreach ($exprs as $expr)   {          $elex = new ELLexer($expr);   $elex->lex();   $parser = new ParserMachine ($elex, $parsertable, $parserproductions);   $parser->run($call);   $result = $call->getAST();   $call->reset();   } } $endTime = microtime(true); $time = $endTime - $startTime; print( "Time elapsed: " . $time . "\n"); 

yml@humility:expressionLanguage$ php --version PHP 5.5.3-1ubuntu2 (cli) (built: Oct  9 2013 14:49:12)  Copyright (c) 1997-2013 The PHP Group Zend Engine v2.5.0, Copyright (c) 1998-2013 Zend Technologies     with Zend OPcache v7.0.3-dev, Copyright (c) 1999-2013, by Zend Technologies 

yml@humility:expressionLanguage$ hhvm --version HipHop VM v2.3.0-dev (rel)  Compiler: heads/master-0-gfc37017a7e1a7d3fa835c3e09a2937f6f4f703ce  Repo schema: 5a59384aec1e7bb9b316f27ae87d6c2a5cd57f76

yml@humility:expressionLanguage$ php ./test.php Time elapsed: 5.0141038894653

yml@humility:expressionLanguage$ hhvm test.php Time elapsed: 5.5141990184784

Time elapsed: 5.0715029239655 Time elapsed: 5.067526102066 Time elapsed: 5.0686640739441 Time elapsed: 5.1444919109344 Time elapsed: 5.0798120498657 Time elapsed: 5.0674719810486 Time elapsed: 5.0758039951324 Time elapsed: 5.0680429935455 Time elapsed: 5.0671808719635 Time elapsed: 5.1225011348724 Time elapsed: 5.0637631416321 Time elapsed: 5.0711719989777 Time elapsed: 5.0798349380493 Time elapsed: 5.0700869560242 Time elapsed: 5.0699179172516

Time elapsed: 5.9072468280792 Time elapsed: 5.9045979976654 Time elapsed: 5.8999648094177 Time elapsed: 5.8969769477844 Time elapsed: 5.8965940475464 Time elapsed: 5.8854668140411 Time elapsed: 5.8934369087219 Time elapsed: 5.8918490409851 Time elapsed: 5.8934841156006 Time elapsed: 5.8858242034912 Time elapsed: 5.8903369903564 Time elapsed: 1.5902738571167 Time elapsed: 1.5128128528595 Time elapsed: 1.5166771411896 Time elapsed: 1.5109701156616 

real0m13.919s

real0m17.138s

real0m0.876s

real0m18.848s

real0m17.899s

real0m3.764s

real0m2.269s

real0m2.992s

real0m4.573s

I'm getting a little closer to fielding Miles By Motorcycle on the HipHopVM (a.k.a. hhvm) stack. I, however, ran into a last minute snag having to do with some disconcerting warning messages in the error log:

HipHop Warning: Invalid argument: function: not a valid callback array

hhvm is much better than PHP at generating meaningful warnings about potential issues in your code. I was a little troubled by this message, however, since it did not provide me a call stack or even a function name. I always suspect my own code and understandings first, so I was fairly convinced it was something I was doing. It turned out to be an hhvm issue in that the custom session close handler was getting called twice. I originally tried using GDB to track through the code, but this was getting me nowhere I switched to configuring the hhvm debugger.

Unfortunately, this was not straightforward since there are a few gotchas.

The hhvm debugger can be invoked in two ways. You can run it interactively to debug local scripts, which in my case is of little use, or you can debug requests coming in from the browser. The latter case, once it works, is extremely cool.

Misconceptions

From the documentation I had a few misconceptions:

• There is a "-m debug" switch for hhvm to enable the debugger, but this does not, by itself allow you to debug server requests.
  
  
• You configure the server to enable remote debugging but you must use a second instance of hhvm called with "-m debug" and connect it to the first.
  
  
• You cannot, to the best of my knowledge, get access to the threads serving requests on the live site. You must set up a debugging "sandboxes".
  
  
• "sandboxes" consist of a user name and a sandbox name and these must be included in the hostname part of the URL you use to pull the page. The sandbox name refers to an entry in a .hphp file in the users home directory.
  
  
• The documentation shows the format of the .hphp file as [sandbox].path=... but the format is actually sandbox.path= where sandbox gets replaced by the name of the sandbox.
  
  
• Each sandbox gets it's own document root, access log and error log that are completely separate from the main site. In my case I just created a symlink to my sites DOCUMENT_ROOT and called it done.
  
  
• It does not appear that you have access to rewriting rules from sandboxes making debugging a full site somewhat challenging.
  
  
• The user account that you run the debugger as (using the -u option) should match the name of your sandbox account to avoid a nasty hanging issue when running the server and debugger on the same machine.
  

Configuring the HHVM Server for Debugging

There are a few steps involved to configure the server.

Sandbox Account and Hostname

The sandbox user account and sandbox name must be included in the hostname part of web requests made to your sandbox server. i.e. http://sandbox_user-sandbox_name.something.com/test.php.

There are probably other ways to do it as the hhvm Debugger unit tests imply, but in my case it was easier to just add an entry in /etc/hosts for my sandbox account name.

Sandbox names are split on a - and have the form sandbox_user-sandbox_name. If no sandbox_name is included, then the name 'default' is used for the sandbox.

Since I'm only working on one site right now, I added a user 'sandbox' to my machine and added a sandbox.mbymc.com entry to /etc/hosts. (replace mbymc with whatever domain your machine is on)

127.0.0.1 sandbox.mbymc.com

If I were working on more than one codebase, I could set up separate sandboxes like 'sandbox-site1', 'sandbox-site2', etc.

The HHVM Server Config File

Refer to the runtime options Sandbox Environment section: https://github.com/facebook/hhvm/wiki/runtime-options#sandbox-environment

You have to add a few blocks to your config.hdf.

Sandbox

Add this block to your servers config.hdf:

Sandbox{SandboxMode = truePattern = ([^-]*(-[^-]*)?).mbymc.comHome = /homeConfFile = .hphp}

Based on my testing, it looks like SandBoxMode must be set to true for this to be enabled.

The idea behind the Pattern setting is that it's a regex that must separate out two matches, one for the user account part and one for the optional sandbox name part. As I mentioned above, if there is no sandbox name part, the name 'default' is used.

The Home path is prepended to whatever the account name is and is used to search for the .hphp file. For example, if the request from the browser contains sandbox-site1.mbymc.com, the .hphp file for that request will be looked for in /home/sandbox/.hphp.

Eval.Debugger

Add the following section after the Sandbox section:

Eval.Debugger
{
EnableDebugger = true
EnableDebuggerServer = true
Port = 8089
DefaultSandboxPath = /path/to/docroot
}

The Sandbox Configuration File .hphp

The sandbox configuration file resides in the home directory of whatever account you're using for your sandbox. In my case I created a /home/sandbox account for this purpose. I created the file

/home/sandbox/.hphp

This file contains name/value pairs that define your various sandboxes for that account.

default.path = www
default.log = error_log
default.accesslog = access_log

The path is relative to the home directory so I simply created a symlink from www to the DOCUMENT_ROOT of my site. You can have entries for multiple sandboxes. If you had an additional site, you could, for instance, add:

site1.path = www2
site1.log = site1_error.log
site1.accesslog = access_log

Testing the Sandbox

Fire up your newly configured hhvm server

hhvm --config /usr/local/etc/hhvm_debugger.hdf -m server

Create a test.php file in the DOCUMENT_ROOT of your sandbox. Have it do something like print hello:

<?php
print( "<p>Hello</p>" );

Now load the file from your browser. In my case, the url was http://sandbox.mbymc.com/test.php.

You should see some output on the page.

Using the hhvm Debugger

Make sure that you pull a page from your sandbox server BEFORE proceeding from this point. Once you have pulled a page, you can now attach a debugger to the sandbox.

Fire up the debugger in a separate terminal window.

Enter the following command:

hhvm -m debug -h localhost -u sandbox_user

where sandbox_user is whatever user you chose to host your sandbox.

NOTE: Specifying the right user seems to be key in making this work correctly. Originally I would run the debugger under whatever user account I was in at the time and I would notice that the debugger would hang indefinitely on the attach step below more times than not. After trial and error, it seems that specifying the sandbox user on the debugger command line (instead of listing and attaching to sandbox instances) avoids this problem.

You should see:

Welcome to HipHop Debugger!

Type "help" or "?" for a complete list of commands.

Connecting to localhost:8089...
Attaching to sandbox's default sandbox and pre-loading, please wait...
localhost>

NOTE: You may need to run with root permissions to avoid a permissions error here. YMMV.

Refer to the Debugger overview documents here:https://github.com/facebook/hhvm/blob/master/hphp/doc/debugger.start https://github.com/facebook/hhvm/blob/master/hphp/doc/debugger.refs

You can now set a breakpoint to fire at the beginning of every request.

break start

You should see:

Breakpoint 1 set start of request.

Enter:

continue

Now reload your sandbox page. You should also notice that the webpage is just hanging waiting for a response.

In the debugger you should see:

Web request /test.php started.

To let the request complete, you can enter the command:

continue

You will notice that the prompt does not return after you do this. Reload the sandbox page in your browser in order to trigger the breakpoint and get the prompt back.

You can also press CTRL-C to get the debugger prompt back. This works as long as the debugger is running as the same user as the sandbox (at least in the case where both are running on the same physical machine).

From this point forward the debugger works as you would expect. You can set breakpoints, inspect variables and even execute arbitrary code.

Conclusion

In crawling around using GDB when I was looking at the HHVM source one of the traces seemed to indicate HHVM was trying to call a NULL custom session close handler. So I created a test file which is included on this issue:https://github.com/facebook/hhvm/issues/1316. It's just a dummy custom session handler.

In the debugger, I made sure to set a start of request breakpoint.

break start

I loaded the page implementing my test_session_handler.php test and the page load was interrupted at the start.

Web request /test_session_handler.php started.

I could now set a breakpoint at the start of _session_close():

break test_session::_session_close()

Which replied:

Breakpoint 3 set upon entering test_session::_session_close()
But wont break until class test_session has been loaded.

Now at the prompt I could enter

continue

which caused the breakpoint to fire on session close which displayed:

13 {
14* print( "session close<br>" );
15 return true;

More docs on using the debugger:https://github.com/facebook/hhvm/blob/master/hphp/doc/debugger.start https://github.com/facebook/hhvm/blob/master/hphp/doc/debugger.refs

You can follow me on twitter: http://twitter.com/yermolamers

Years ago, faced with the need to build and manage a number of content websites, I developed a novel content management system akin to what Joomla or Drupal are today. I've always run my own servers so I could have chosen any development language. I briefly considered Java. However, suffering from delusions of grandeur, I wanted to make certain that whatever I built was as widely installable as possible. I envisioned building a successful open source platform that I could then build a services company around. Low cost hosting featuring Apache, PHP and Mysql were abundant. Many people getting into programming were learning PHP. My feeling was PHP would take off, so I decided to adopt that language despite thinking it smelled funny. I second guessed myself, as I am want to do, and feared putting in huge amount of work only to have the platform it was built upon become non-viable. I knew the majority of the work would actually be in building the forms and views that made up the system. To hedge my bets, I created a pedestrian XML "web component description" language that allowed me to describe the forms, views, validation, and business logic. This isolated me from relying on PHP too much. I called this language the formVista Markup Language or FVML. Honestly, I always thought the PHP implementation would just be a prototype. My thinking was that eventually I would just rewrite the parser in some other better language because obviously only a madman implements a web development language in PHP.

Reimplementing the parser never happened because for all the projects that I needed, this codebase ended up being "good enough". I still prefer it to Wordpress, Joomla or Drupal. I decided to try and build Miles By Motorcycle on it because I still prefer it to those other platforms. (I really tried. I even installed Wordpress. I did a project in Drupal and even evaluated Diaspora.) In retrospect, I probably should have chosen other technologies and approaches since M-BY-MC doesn't need to be "installable" in the way the code needed to be before. Unfortunately, M-BY-MC highlights just how badly my legacy platform performs when stressed.

Pages are loading wickedly slowly and it's primarily in evaluating expressions in my FVML language because PHP's string handling is so slow. I really didn't want to rewrite the expression parser in C++. As a fallback I was going to write a "compiler" for FVML to translate it into static PHP instead of building the parse trees on the fly.

Enter Facebook's HipHopVM JIT Compiler

Facebook had an analogous problem. Programmers who only know PHP are relatively inexpensive to hire. Facebook hires bunches of them. But there's a cost in terms of hardware. Facebook has to run more hardware as a result of the inefficient PHP stack. So Facebook embarked on the insanity of building their own from the ground up complete PHP stack in-house. Originally this took the form of HipHop, a PHP to C++ translator which yielded around a factor of 5 performance improvement. The problem with HipHop was that it was a different development process. You couldn't just edit your files and immediately see the result. You had to compile and re-run.

So, expanding on their insanity because we all know it's simply not possible for any mortal to accomplish, Facebook boldly took the additional step of turning their PHP to C++ translator into a full fledged PHP to Native Binary Just In Time (JIT) compiler. This is nuts. It even features an integrated web server. Now, the development process was the same as with the original PHP stack. Just edit a file and load the page in your browser.

The original PHP in Apache uses up a bunch of RAM. A separate fork of Apache handles each page request. The PHP interpreter is constructed, the PHP files are loaded, compilied into bytecode, the bytecode is intepreted, output is generated and PHP is torn down again on each request. You can get it to skip the compiling into bytecode step for some modest performance gain.

HipHopVM is vastly better designed in that it's a multi-threaded long lived single instance. It loads everything once and then just checks to see if it's changed. After running a given PHP file a few times, it then compiles it to native binary code which is directly executable. This code is cached. It's only updated if the source PHP file changes. This alone represents a huge performance gain.

One of the developers told me that because they run the code first a few times they can do some profiling of a sort to actually generate more optimized binary code than a static compiler can in some if not many instances. There were some cases where PHP code run in HipHopVM ran faster than the equivalent C++ code.

We know this is not possible, but they have done it anyway.

Crash Testing HipHopVM with the Miles By Motorcycle Codebase

Of course, I knew there was simply no way in hell that HipHopVM was going to be able to run my codebase. But I was curious to give it a try to see how badly things broke.

The Miles By Motorcycle project now consists of over 500 PHP files and some 1200 FVML files in addition to a bunch of javascript, support scripts and static assets not to mention a modestly complicated MySQL backend. I do my own file loading and have a custom session manager. There's even a complete setup script.

It's a herculean effort to create something with parity to the massive number of extensions written for PHP. However, I was impressed by how many extensions they already supported. Luckily for me, because I was suspicious of PHP I limited my reliance on extensions whenever possible and this served me well as HHVM already supports all the extensions I need: mysql, gd, session, pcre, posix, xml, hash, imap, openssl, exif

I pulled down the binary distribution. I couldn't figure out how to get the rewrite rules working, so I just decided to see if it could run the setup script, parts of which were itself written in FVML which means the entire parser and all that support code would get tested. There was no way this was going to work.

Imagine my shock and horror when HipHopVM executed all the pages of my setup script including setting up the databases flawlessly!

Needless to say I was incredibly impressed.

I searched around github and on the web to get more information about the weird configuration file format HipHopVM uses. There wasn't much out there but with some trial and error I managed to get the public homepage of the site to load and was able to navigate around the site. Impressive.

The Problems I Ran Into

JIT Bug

It wasn't all trouble free. The first problem I ran into was a HipHopVM crash on a certain page. I joined the IRC channel where it was said the developers tend to hang out. I lurked for a while to see how the conversations went. The instructions there are to type hhvm-help: with a question to get their attention.

While I didn't really expect a response, I did give it a try and to my great surprise I was immediately chatting with someone from Facebook who was taking my crash report very seriously.

I have to say everyone I have chatted with over there has been extremely nice, professional, and helpful. Despite being busy and deluged with lots of help requests, they were always pleasant and seemed honestly interested in helping. I have to say I appreciate it.

They gave me a few tests to run which required me to pull down the source and go through building the environment. This took quite a bit of time. Then came loading hhvm in GDB and giving them dumps. Interestingly, there are some options which you can provide when building which will enable GDB to display the PHP source line an HHVM crash happens on. You have to configure for debugging using cmake -DCMAKE_BUILD_TYPE=Debug . Then when you run the server add the options -vEval.SyncGdbChunks=1 -vEval.JitNoGdb=false

Very cool.

Dutifully, I went back and reported my findings. We went through a few more interations and they found the problem. It turns out I was doing something unanticipated but valid in one method, although they did not tell me what, and this was causing the JIT compiler to generate some bad code. Instead of telling me to change my code, they fixed the compiler and gave me a patch.

Awesome.

Custom Session Handler Support

The second problem I ran into was another crash bug. This one would manifest itself in between 3 and 5 page loads regardless of whether it was a same page reload or navigating through the site. Knowing a bit more this time, I was able to figure out that it was happening in my session handler. PHP allows you to override the default session handler to add in your own, which I do.

This bug had been reported. It's been a little while ago now, but if I remember correctly it was a repeat of my previous experience. Run some tests and report GDB dumps back. Try a patch. Again, everyone was so nice and helpful. After a few days, this bug was also fixed.

get_html_translation_table()

HipHopVM currently does not implement this function correctly. It returns garbage results. For this one, since it was clearly a bug (where as the two others before could easily have been something I was doing wrong), I filed a bug report. https://github.com/facebook/hhvm/issues/1100

One of the guys I had been chatting with in the IRC channel replied saying that this was a low priority for them but they would be grateful if I took a crack at it.

It's been 10 years since I've done any C++ and I haven't worked on a body of code this involved in a long time, but I dove in to see if I could get a handle on the codebase. While it's extremely lacking in comments or documentation, it is pretty well organized and the source files are clean. GDB, of course, doesn't know about the data structures in the code and can only give you basic types back. I asked if there was a way to inspect some of the larger data types and they quickly sent me some python scripts to source into GDB that allows you to view some of them. GDB has come a long long way. I eventually found the code that's misbehaving but not being that familiar with UNICODE implementations I figured I'd best leave it alone and just work around it in my code. I may go back to it and see if I can fix it in hhvm.

Note: HipHopVM defines HPHP_VERSION which you can test for in your PHP code for those rare instances where you need to work around some hhvm limitation or difference.

imap_rfc822_parse_adrlist()

Interestingly, hhvm defines this function so that if you check for it's existence it will say it's there. i.e. function_exists("imap_rfc822_parse_adrlist") returns true. However, if you then call the function is raises a nasty exception because the function is just a stub that has not been filled in yet. So in an email class, I had to check for this and use a PHP implementation of the function instead.

The Fast Path Problem

This one took by far the longest to track down.

The Miles By Motorcycle codebase relies heavily on URL rewriting and this was working perfectly. However, I want to keep the option of running the same site on the old Apache and Zend PHP stack in case I run into problems with HHVM. This means I want to leave all my .htaccess files lying around but don't want hhvm to server them.

So I thought I could simply write a rewrite rule to present a 404 page when a .htaccess file request is made.

This did not work. No matter what I tried I could not get this to work and then, after some investigation, I realized rewriting only works if the source URL does not represent a file in the filesystem. For example, you can write a rewrite rule from image1.gif to image2.gif but only if image1.gif does not exist. If image1.gif exists in the filesystem, the rewriting rules get bypassed and image1.gif is served immediately.

This seemed very strange so I once again joined the developers in IRC and posted the question. They agreed it was likely a bug so I filed an issue. https://github.com/facebook/hhvm/issues/1283

Unfortunately for me, the team is currently focusing on getting FastCGI support ready so they won't have time to focus on this issue but mentioned that if I wanted to submit a patch they'd be happy to review it.

I didn't want to wait several months for FastCGI to work well and I thought if I could just get this issue resolved I'd be much closer to having a fully functional HHVM install. The code is so well organized it took me probably less than 15 minutes to find the offending function and to verify, thanks to a helpful comment, that in fact there was a "fast path" optimization that just automatically serves the file if it's present bypassing rewriting rules. The developers had asked that any changes I make should be governed by an additional configuration option and that the current behavior should remain the default. The config file handling is not as straight forward as I would like it to be but I found that I could easily add an option at the VirtualHost level. I submitted my first pull request. I had called the option StaticFastPath but they pointed out the same problem existed with PHP files, which I missed. So the option was renamed CheckExistenceBeforeRewrite and it is true by default to maintain the original behavior. The pull request was accepted so a few lines of code I wrote are in HHVM and I'm on the list of contributors.

Sometimes it's the little things in life, right? If this makes it onto Facebook's servers, the one if statement I wrote, which is invoked in every request, will be the most widely used code fragment I have ever written. Weird and somewhat depressing.

Setting CheckExitenceBeforeRewrite to false gets you the behavior you would expect coming from Apache mod_rewrite.

Configuration and Rewrite Rules

Once CheckExistenceBeforeRewrite was added to the codebase I could get my rewriting rules working. HHVM's configuration file is in an odd format called hdf which looks like some badly form JSON. The documentation is horrible and searching online quite a few people are running into problems working with it. I suspect it was, for many people, the odd rewrite bypass that was tripping them up. I could be mistaken.

Some things about the configuration file that confused me were:

• sometimes names of sections are meaningful and sometimes they are not. When they are not an * is used apparently as a placeholder.
  
  
• EnableStaticContentCache in the Server {} section does not seem to work. HHVM is unresponsive for an extended period and the process grows to be huge. I have not yet tracked this down or filed an issue about it. I just set it to false.
  
  
• Setting FileCache in the Server {} section seems to break caching.
  
  
• I need to explicitly set the PidFile in the Server {} section.
  
  
• The DefaultServerNameSuffix setting in the Server {} section seems to break $_SERVER['SERVER_NAME']. I leave it blank.
  
  
• In Rewrite rules there is a a condition {} block which is used identify items that you do NOT want to match. Think of it as an "except". Rewrite all of these URLs "except" the ones in the condition block. You must include negate = true in the condition block. I'm not sure what negate = false would be used for in this context.
  
  
• Rewrite rules are in fact applied in the order they appear in the configuration.
  
  
• In order to rewrite rules for files that exist, like to hide .htaccess files, make sure CheckExistenceBeforeRewrite is set to false.
  

Here's a santized version of the config that I have working on my development machine with some comments:

# HipHopVM configuration file for http://miles-by-motorcycle.com## This is a structured config file format. ## '*' is used as a placeholder where hiphopvm doesn't care what's # present. More descriptive # strings could be used in their place.## See https://github.com/facebook/hiphop-php/wiki/Runtime-options for # more, albeit incomplete, info. ## I have a large legacy PHP codebase that is in dire need of some # performance improvements. It's a content management/social networking# platform supporting user profiles, facebook logins, friends lists,# privacy, a search engine, blog, discussion forum, photo gallery, # interactive mapping, tagging of locations and routes, among many # other features. I've been working on for some time.  It consists # of 2958 PHP files including a number of third party projects # including htmlpurifier, markdownify, ImageManager, and Xinha to name # a few.## The number of PHP extensions used has been kept to an absolute minimum # making it easier to install this codebase on client servers and shared # hosting environments:## mysql, gd, session, pcre, posix, xml, hash, imap, openssl, exif## It's divided into a frontend where all content is served dynamically # through rewriting rules and a backend admin section. Cachebusting of # static files is supported.## To date it's been running under Apache and Zend PHP and makes heavy # use of mod_rewrite. ## This config represents my efforts to get this legacy codebase working # under HHVM. There is very little documentation so much has been # determined through trial and error. There are many config options I # have not experimented with.## HHVM does support VirtualHosts and rewrite rules but it's not well # documented and there was at least one bug preventing it from working, # which has been fixed:## https://github.com/facebook/hhvm/issues/1283## Yermo Lamers## github.com/Yermo# twitter.com/yermolamers# facebook.com/yermo# miles-by-motorcycle.com/yermo# ---------------------------------------------------------------------Eval {   # set to true to enable JIT compiler   # If hhvm crashes you can turn this off to see if the problem    # is in the JIT.   Jit = true}# --------------------------------------------------------------------# access and error loggingLog {#   Level = Error#   NoSilencer = false   AlwaysLogUnhandledExceptions = true   RuntimeErrorReportingLevel = 8191#   Header = false   InjectedStackTrace = true   NativeStackTrace = true #   MaxMessagesPerRequest = -1   # error log settings   UseLogFile = true   File = /var/log/hhvm/error.log   # access log settings   AccessLogDefaultFormat = %h %l %u %t "%r" %>s %b   Access {      * {         File = /var/log/hhvm/access.log         Format = %h %l %u %t \"%r\" %>s %b      }   }   # admin server logging   AdminLog {      File = /var/log/hhvm/admin_access.log      Format = %h %t %s %U   }   # enable or disable hphp_log() that can be called from PHP code   ApplicationLog = true} # end of Log# ===================================PidFile = /var/log/hhvm/hhvm.pid# ---------------------------------------------------------------------# Server wide settings.Server {   Host = miles-by-motorcycle.yml.com   # IP = 0.0.0.0   Port = 80   # ThreadCount = 50   SourceRoot = /var/www/miles-by-motorcycle.com/html/   # If ServerName is not specified for a virtual host, use prefix + this   # suffix to compose one   # 2013-11-18: NOTE this seems to get appended to $_SERVER["SERVER_NAME"]   # DefaultServerNameSuffix = some.com   # Forcing $_SERVER['SERVER_NAME'] to come from request header   ForceServerNameToHeader = false   # startup options   DefaultDocument = index.php   # make sure your RewriteRules in the VirtualHost section take 404's    # into account. The same goes for favicon.ico.   ErrorDocument404 = error404.html   FatalErrorMessage = "Fatal Error"   # shutdown options   GracefulShutdownWait = 0   # in seconds   HarshShutdown = true   EvilShutdown = true   DanglingWait = 0   # HTTP settings   GzipCompressionLevel = 3   EnableMagicQuotesGpc = false   EnableKeepAlive = true   EnableEarlyFlush = true   ForceChunkedEncoding = false   MaxPostSize = 24  # in MB   LibEventSyncSend = true   ResponseQueueCount = 0   # static contents   # Setting this explicitly seems to break the cache.   #   # FileCache = /usr/local/WWW/miles-by-motorcycle.com/cache   # EnableStaticContentCache worked for me in a previous version   # of hhvm, but recent builds haven't worked. I don't know if   # there is a way to control what gets cached and what doesn't.   EnableStaticContentCache = false   EnableStaticContentFromDisk = true   ExpiresActive = true   ExpiresDefault = 2592000   DefaultCharsetName = UTF-8   # file access control   SafeFileAccess = false}  # end of server# ---------------------------------------------------------------------AdminServer {   Port = 8088   ThreadCount = 1   Password = set_password_here}# end of admin server# ---------------------------------------------------------------------# Virtual Host DefinitionsVirtualHost {   * {      # strangely by default, hhvm will bypass rewrite rules       # if the file exists. (So you can't rewrite image1.gif       # to image2.gif if image1.gif exists.)      # This turns off that behavior.      #      # See https://github.com/facebook/hhvm/issues/1283      CheckExistenceBeforeRewrite = false      # which requests should this virtual host definition       # apply to? In my case, I have one site so everything       # goes through this virtual host.      Pattern = .*      # URL rewriting rules are applied in the order listed.       # The first rule that matches is applied.      RewriteRules {         # cachebust rewriting rules example         #         # In my app I send out css, js and ico files          # with a cachebust timestamp.          #         # For example, favicon.ico gets served as          # favicon.cb1234567.ico. So when the request          # comes back in to the server I need to map          # the cachebusted request to the original file          # name.          * {            pattern = ^(.*).cb([0-9]+).(css|js|ico)$            to = $1.$3            # do not append any query strings.                 qsa = false          }         # In my app I have a public side and and admin          # side. All requests to the public side should          # be rerouted through a script. All requests to         # the backend .php and static asset files should         # be allowed.         * {            # rewrite every request onto             # /myapp/page.php/<original request>            pattern = ^(.*)$            to = /myapp/page.php/$1            # append any query strings.            qsa = true            # we don't want this rewrite rule to be fired for static             # content such as images. Anything that matches the            # section below will NOT be rewritten.            #            # Note that if we fall through these rules and the file was            # not found, hhvm will attempt to serve the error404.html             # page, per config above. It will fall back through to the            # rewrite rule above dynamically serve the 404 page from my             # code.            conditions {                   * {                     # allow php and static asset files to be linked to                     # directly, otherwise any other requests get run                      # through the rewrite rule above and will generate                     # file not found errors.                     pattern = ^(/myapp/.*php|.*\.(css|js|jpg|gif|ico|png|jpeg|json))$                     # when set to true causes the wrapping rewrite                      # rule to be ignored when the pattern is matched.                     negate = true                  }               }            # end of conditions         }      }      # end of RewriteRules   }}# end of VirtualHost # ---------------------------------------------------------------------# PHP Debugging/Logging#Debug {   # when errors are logged include a full PHP backtrace (useful for    # debugging)   FullBacktrace = true   ServerStackTrace = true   ServerErrorMessage = true   TranslateSource = false    RecordInput = false   ClearInputOnSuccess = true   ProfilerOutputDir = /tmp   # CoreDumpEmail = email address   CoreDumpReport = true}# ---------------------------------------------------------------------# Static File Mime Types## from: https://gist.github.com/simonwelsh/6442425StaticFile {   Extensions {      123 = application/vnd.lotus-1-2-3      3dml = text/vnd.in3d.3dml      3ds = image/x-3ds      3g2 = video/3gpp2      3gp = video/3gpp      7z = application/x-7z-compressed      aab = application/x-authorware-bin      aac = audio/x-aac      aam = application/x-authorware-map      aas = application/x-authorware-seg      abw = application/x-abiword      ac = application/pkix-attr-cert      acc = application/vnd.americandynamics.acc      ace = application/x-ace-compressed      acu = application/vnd.acucobol      acutc = application/vnd.acucorp      adp = audio/adpcm      aep = application/vnd.audiograph      afm = application/x-font-type1      afp = application/vnd.ibm.modcap      ahead = application/vnd.ahead.space      ai = application/postscript      aif = audio/x-aiff      aifc = audio/x-aiff      aiff = audio/x-aiff      air = application/vnd.adobe.air-application-installer-package+zip      ait = application/vnd.dvb.ait      ami = application/vnd.amiga.ami      apk = application/vnd.android.package-archive      appcache = text/cache-manifest      application = application/x-ms-application      apr = application/vnd.lotus-approach      arc = application/x-freearc      asc = application/pgp-signature      asf = video/x-ms-asf      asm = text/x-asm      aso = application/vnd.accpac.simply.aso      asx = video/x-ms-asf      atc = application/vnd.acucorp      atom = application/atom+xml      atomcat = application/atomcat+xml      atomsvc = application/atomsvc+xml      atx = application/vnd.antix.game-component      au = audio/basic      avi = video/x-msvideo      aw = application/applixware      azf = application/vnd.airzip.filesecure.azf      azs = application/vnd.airzip.filesecure.azs      azw = application/vnd.amazon.ebook      bat = application/x-msdownload      bcpio = application/x-bcpio      bdf = application/x-font-bdf      bdm = application/vnd.syncml.dm+wbxml      bed = application/vnd.realvnc.bed      bh2 = application/vnd.fujitsu.oasysprs      bin = application/octet-stream      blb = application/x-blorb      blorb = application/x-blorb      bmi = application/vnd.bmi      bmp = image/bmp      book = application/vnd.framemaker      box = application/vnd.previewsystems.box      boz = application/x-bzip2      bpk = application/octet-stream      btif = image/prs.btif      bz = application/x-bzip      bz2 = application/x-bzip2      c = text/x-c      c11amc = application/vnd.cluetrust.cartomobile-config      c11amz = application/vnd.cluetrust.cartomobile-config-pkg      c4d = application/vnd.clonk.c4group      c4f = application/vnd.clonk.c4group      c4g = application/vnd.clonk.c4group      c4p = application/vnd.clonk.c4group      c4u = application/vnd.clonk.c4group      cab = application/vnd.ms-cab-compressed      caf = audio/x-caf      cap = application/vnd.tcpdump.pcap      car = application/vnd.curl.car      cat = application/vnd.ms-pki.seccat      cb7 = application/x-cbr      cba = application/x-cbr      cbr = application/x-cbr      cbt = application/x-cbr      cbz = application/x-cbr      cc = text/x-c      cct = application/x-director      ccxml = application/ccxml+xml      cdbcmsg = application/vnd.contact.cmsg      cdf = application/x-netcdf      cdkey = application/vnd.mediastation.cdkey      cdmia = application/cdmi-capability      cdmic = application/cdmi-container      cdmid = application/cdmi-domain      cdmio = application/cdmi-object      cdmiq = application/cdmi-queue      cdx = chemical/x-cdx      cdxml = application/vnd.chemdraw+xml      cdy = application/vnd.cinderella      cer = application/pkix-cert      cfs = application/x-cfs-compressed      cgm = image/cgm      chat = application/x-chat      chm = application/vnd.ms-htmlhelp      chrt = application/vnd.kde.kchart      cif = chemical/x-cif      cii = application/vnd.anser-web-certificate-issue-initiation      cil = application/vnd.ms-artgalry      cla = application/vnd.claymore      class = application/java-vm      clkk = application/vnd.crick.clicker.keyboard      clkp = application/vnd.crick.clicker.palette      clkt = application/vnd.crick.clicker.template      clkw = application/vnd.crick.clicker.wordbank      clkx = application/vnd.crick.clicker      clp = application/x-msclip      cmc = application/vnd.cosmocaller      cmdf = chemical/x-cmdf      cml = chemical/x-cml      cmp = application/vnd.yellowriver-custom-menu      cmx = image/x-cmx      cod = application/vnd.rim.cod      com = application/x-msdownload      conf = text/plain      cpio = application/x-cpio      cpp = text/x-c      cpt = application/mac-compactpro      crd = application/x-mscardfile      crl = application/pkix-crl      crt = application/x-x509-ca-cert      cryptonote = application/vnd.rig.cryptonote      csh = application/x-csh      csml = chemical/x-csml      csp = application/vnd.commonspace      css = text/css      cst = application/x-director      csv = text/csv      cu = application/cu-seeme      curl = text/vnd.curl      cww = application/prs.cww      cxt = application/x-director      cxx = text/x-c      dae = model/vnd.collada+xml      daf = application/vnd.mobius.daf      dart = application/vnd.dart      dataless = application/vnd.fdsn.seed      davmount = application/davmount+xml      dbk = application/docbook+xml      dcr = application/x-director      dcurl = text/vnd.curl.dcurl      dd2 = application/vnd.oma.dd2+xml      ddd = application/vnd.fujixerox.ddd      deb = application/x-debian-package      def = text/plain      deploy = application/octet-stream      der = application/x-x509-ca-cert      dfac = application/vnd.dreamfactory      dgc = application/x-dgc-compressed      dic = text/x-c      dif = video/x-dv      dir = application/x-director      dis = application/vnd.mobius.dis      dist = application/octet-stream      distz = application/octet-stream      djv = image/vnd.djvu      djvu = image/vnd.djvu      dll = application/x-msdownload      dmg = application/x-apple-diskimage      dmp = application/vnd.tcpdump.pcap      dms = application/octet-stream      dna = application/vnd.dna      doc = application/msword      docm = application/vnd.ms-word.document.macroenabled.12      docx = application/vnd.openxmlformats-officedocument.wordprocessingml.document      dot = application/msword      dotm = application/vnd.ms-word.template.macroenabled.12      dotx = application/vnd.openxmlformats-officedocument.wordprocessingml.template      dp = application/vnd.osgi.dp      dpg = application/vnd.dpgraph      dra = audio/vnd.dra      dsc = text/prs.lines.tag      dssc = application/dssc+der      dtb = application/x-dtbook+xml      dtd = application/xml-dtd      dts = audio/vnd.dts      dtshd = audio/vnd.dts.hd      dump = application/octet-stream      dv = video/x-dv      dvb = video/vnd.dvb.file      dvi = application/x-dvi      dwf = model/vnd.dwf      dwg = image/vnd.dwg      dxf = image/vnd.dxf      dxp = application/vnd.spotfire.dxp      dxr = application/x-director      ecelp4800 = audio/vnd.nuera.ecelp4800      ecelp7470 = audio/vnd.nuera.ecelp7470      ecelp9600 = audio/vnd.nuera.ecelp9600      ecma = application/ecmascript      edm = application/vnd.novadigm.edm      edx = application/vnd.novadigm.edx      efif = application/vnd.picsel      ei6 = application/vnd.pg.osasli      elc = application/octet-stream      emf = application/x-msmetafile      eml = message/rfc822      emma = application/emma+xml      emz = application/x-msmetafile      eol = audio/vnd.digital-winds      eot = application/vnd.ms-fontobject      eps = application/postscript      epub = application/epub+zip      es3 = application/vnd.eszigno3+xml      esa = application/vnd.osgi.subsystem      esf = application/vnd.epson.esf      et3 = application/vnd.eszigno3+xml      etx = text/x-setext      eva = application/x-eva      evy = application/x-envoy      exe = application/x-msdownload      exi = application/exi      ext = application/vnd.novadigm.ext      ez = application/andrew-inset      ez2 = application/vnd.ezpix-album      ez3 = application/vnd.ezpix-package      f = text/x-fortran      f4v = video/x-f4v      f77 = text/x-fortran      f90 = text/x-fortran      fbs = image/vnd.fastbidsheet      fcdt = application/vnd.adobe.formscentral.fcdt      fcs = application/vnd.isac.fcs      fdf = application/vnd.fdf      fe_launch = application/vnd.denovo.fcselayout-link      fg5 = application/vnd.fujitsu.oasysgp      fgd = application/x-director      fh = image/x-freehand      fh4 = image/x-freehand      fh5 = image/x-freehand      fh7 = image/x-freehand      fhc = image/x-freehand      fig = application/x-xfig      flac = audio/x-flac      fli = video/x-fli      flo = application/vnd.micrografx.flo      flv = video/x-flv      flw = application/vnd.kde.kivio      flx = text/vnd.fmi.flexstor      fly = text/vnd.fly      fm = application/vnd.framemaker      fnc = application/vnd.frogans.fnc      for = text/x-fortran      fpx = image/vnd.fpx      frame = application/vnd.framemaker      fsc = application/vnd.fsc.weblaunch      fst = image/vnd.fst      ftc = application/vnd.fluxtime.clip      fti = application/vnd.anser-web-funds-transfer-initiation      fvt = video/vnd.fvt      fxp = application/vnd.adobe.fxp      fxpl = application/vnd.adobe.fxp      fzs = application/vnd.fuzzysheet      g2w = application/vnd.geoplan      g3 = image/g3fax      g3w = application/vnd.geospace      gac = application/vnd.groove-account      gam = application/x-tads      gbr = application/rpki-ghostbusters      gca = application/x-gca-compressed      gdl = model/vnd.gdl      geo = application/vnd.dynageo      gex = application/vnd.geometry-explorer      ggb = application/vnd.geogebra.file      ggt = application/vnd.geogebra.tool      ghf = application/vnd.groove-help      gif = image/gif      gim = application/vnd.groove-identity-message      gml = application/gml+xml      gmx = application/vnd.gmx      gnumeric = application/x-gnumeric      gph = application/vnd.flographit      gpx = application/gpx+xml      gqf = application/vnd.grafeq      gqs = application/vnd.grafeq      gram = application/srgs      gramps = application/x-gramps-xml      gre = application/vnd.geometry-explorer      grv = application/vnd.groove-injector      grxml = application/srgs+xml      gsf = application/x-font-ghostscript      gtar = application/x-gtar      gtm = application/vnd.groove-tool-message      gtw = model/vnd.gtw      gv = text/vnd.graphviz      gxf = application/gxf      gxt = application/vnd.geonext      h = text/x-c      h261 = video/h261      h263 = video/h263      h264 = video/h264      hal = application/vnd.hal+xml      hbci = application/vnd.hbci      hdf = application/x-hdf      hh = text/x-c      hlp = application/winhlp      hpgl = application/vnd.hp-hpgl      hpid = application/vnd.hp-hpid      hps = application/vnd.hp-hps      hqx = application/mac-binhex40      htke = application/vnd.kenameaapp      htm = text/html      html = text/html      hvd = application/vnd.yamaha.hv-dic      hvp = application/vnd.yamaha.hv-voice      hvs = application/vnd.yamaha.hv-script      i2g = application/vnd.intergeo      icc = application/vnd.iccprofile      ice = x-conference/x-cooltalk      icm = application/vnd.iccprofile      ico = image/x-icon      ics = text/calendar      ief = image/ief      ifb = text/calendar      ifm = application/vnd.shana.informed.formdata      iges = model/iges      igl = application/vnd.igloader      igm = application/vnd.insors.igm      igs = model/iges      igx = application/vnd.micrografx.igx      iif = application/vnd.shana.informed.interchange      imp = application/vnd.accpac.simply.imp      ims = application/vnd.ms-ims      in = text/plain      ink = application/inkml+xml      inkml = application/inkml+xml      install = application/x-install-instructions      iota = application/vnd.astraea-software.iota      ipfix = application/ipfix      ipk = application/vnd.shana.informed.package      irm = application/vnd.ibm.rights-management      irp = application/vnd.irepository.package+xml      iso = application/x-iso9660-image      itp = application/vnd.shana.informed.formtemplate      ivp = application/vnd.immervision-ivp      ivu = application/vnd.immervision-ivu      jad = text/vnd.sun.j2me.app-descriptor      jam = application/vnd.jam      jar = application/java-archive      java = text/x-java-source      jisp = application/vnd.jisp      jlt = application/vnd.hp-jlyt      jnlp = application/x-java-jnlp-file      joda = application/vnd.joost.joda-archive      jp2 = image/jp2      jpe = image/jpeg      jpeg = image/jpeg      jpg = image/jpeg      jpgm = video/jpm      jpgv = video/jpeg      jpm = video/jpm      js = application/javascript      json = application/json      jsonml = application/jsonml+json      kar = audio/midi      karbon = application/vnd.kde.karbon      kfo = application/vnd.kde.kformula      kia = application/vnd.kidspiration      kml = application/vnd.google-earth.kml+xml      kmz = application/vnd.google-earth.kmz      kne = application/vnd.kinar      knp = application/vnd.kinar      kon = application/vnd.kde.kontour      kpr = application/vnd.kde.kpresenter      kpt = application/vnd.kde.kpresenter      kpxx = application/vnd.ds-keypoint      ksp = application/vnd.kde.kspread      ktr = application/vnd.kahootz      ktx = image/ktx      ktz = application/vnd.kahootz      kwd = application/vnd.kde.kword      kwt = application/vnd.kde.kword      lasxml = application/vnd.las.las+xml      latex = application/x-latex      lbd = application/vnd.llamagraphics.life-balance.desktop      lbe = application/vnd.llamagraphics.life-balance.exchange+xml      les = application/vnd.hhe.lesson-player      lha = application/x-lzh-compressed      link66 = application/vnd.route66.link66+xml      list = text/plain      list3820 = application/vnd.ibm.modcap      listafp = application/vnd.ibm.modcap      lnk = application/x-ms-shortcut      log = text/plain      lostxml = application/lost+xml      lrf = application/octet-stream      lrm = application/vnd.ms-lrm      ltf = application/vnd.frogans.ltf      lvp = audio/vnd.lucent.voice      lwp = application/vnd.lotus-wordpro      lzh = application/x-lzh-compressed      m13 = application/x-msmediaview      m14 = application/x-msmediaview      m1v = video/mpeg      m21 = application/mp21      m2a = audio/mpeg      m2v = video/mpeg      m3a = audio/mpeg      m3u = audio/x-mpegurl      m3u8 = application/vnd.apple.mpegurl      m3u8 = application/x-mpegurl      m4a = audio/mp4a-latm      m4p = audio/mp4a-latm      m4u = video/vnd.mpegurl      m4v = video/mp4      m4v = video/x-m4v      ma = application/mathematica      mac = image/x-macpaint      mads = application/mads+xml      mag = application/vnd.ecowin.chart      maker = application/vnd.framemaker      man = text/troff      manifest = text/cache-manifest      mar = application/octet-stream      mathml = application/mathml+xml      mb = application/mathematica      mbk = application/vnd.mobius.mbk      mbox = application/mbox      mc1 = application/vnd.medcalcdata      mcd = application/vnd.mcd      mcurl = text/vnd.curl.mcurl      mdb = application/x-msaccess      mdi = image/vnd.ms-modi      me = text/troff      mesh = model/mesh      meta4 = application/metalink4+xml      metalink = application/metalink+xml      mets = application/mets+xml      mfm = application/vnd.mfmp      mft = application/rpki-manifest      mgp = application/vnd.osgeo.mapguide.package      mgz = application/vnd.proteus.magazine      mid = audio/midi      midi = audio/midi      mie = application/x-mie      mif = application/vnd.mif      mime = message/rfc822      mj2 = video/mj2      mjp2 = video/mj2      mk3d = video/x-matroska      mka = audio/x-matroska      mks = video/x-matroska      mkv = video/x-matroska      mlp = application/vnd.dolby.mlp      mmd = application/vnd.chipnuts.karaoke-mmd      mmf = application/vnd.smaf      mmr = image/vnd.fujixerox.edmics-mmr      mng = video/x-mng      mny = application/x-msmoney      mobi = application/x-mobipocket-ebook      mods = application/mods+xml      mov = video/quicktime      movie = video/x-sgi-movie      mp2 = audio/mpeg      mp21 = application/mp21      mp2a = audio/mpeg      mp3 = audio/mpeg      mp4 = video/mp4      mp4a = audio/mp4      mp4s = application/mp4      mp4v = video/mp4      mpc = application/vnd.mophun.certificate      mpe = video/mpeg      mpeg = video/mpeg      mpg = video/mpeg      mpg4 = video/mp4      mpga = audio/mpeg      mpkg = application/vnd.apple.installer+xml      mpm = application/vnd.blueice.multipass      mpn = application/vnd.mophun.application      mpp = application/vnd.ms-project      mpt = application/vnd.ms-project      mpy = application/vnd.ibm.minipay      mqy = application/vnd.mobius.mqy      mrc = application/marc      mrcx = application/marcxml+xml      ms = text/troff      mscml = application/mediaservercontrol+xml      mseed = application/vnd.fdsn.mseed      mseq = application/vnd.mseq      msf = application/vnd.epson.msf      msh = model/mesh      msi = application/x-msdownload      msl = application/vnd.mobius.msl      msty = application/vnd.muvee.style      mts = model/vnd.mts      mus = application/vnd.musician      musicxml = application/vnd.recordare.musicxml+xml      mvb = application/x-msmediaview      mwf = application/vnd.mfer      mxf = application/mxf      mxl = application/vnd.recordare.musicxml      mxml = application/xv+xml      mxs = application/vnd.triscape.mxs      mxu = video/vnd.mpegurl      n3 = text/n3      nb = application/mathematica      nbp = application/vnd.wolfram.player      nc = application/x-netcdf      ncx = application/x-dtbncx+xml      nfo = text/x-nfo      ngdat = application/vnd.nokia.n-gage.data      nitf = application/vnd.nitf      nlu = application/vnd.neurolanguage.nlu      nml = application/vnd.enliven      nnd = application/vnd.noblenet-directory      nns = application/vnd.noblenet-sealer      nnw = application/vnd.noblenet-web      npx = image/vnd.net-fpx      nsc = application/x-conference      nsf = application/vnd.lotus-notes      ntf = application/vnd.nitf      nzb = application/x-nzb      oa2 = application/vnd.fujitsu.oasys2      oa3 = application/vnd.fujitsu.oasys3      oas = application/vnd.fujitsu.oasys      obd = application/x-msbinder      obj = application/x-tgif      oda = application/oda      odb = application/vnd.oasis.opendocument.database      odc = application/vnd.oasis.opendocument.chart      odf = application/vnd.oasis.opendocument.formula      odft = application/vnd.oasis.opendocument.formula-template      odg = application/vnd.oasis.opendocument.graphics      odi = application/vnd.oasis.opendocument.image      odm = application/vnd.oasis.opendocument.text-master      odp = application/vnd.oasis.opendocument.presentation      ods = application/vnd.oasis.opendocument.spreadsheet      odt = application/vnd.oasis.opendocument.text      oga = audio/ogg      ogg = audio/ogg      ogv = video/ogg      ogx = application/ogg      omdoc = application/omdoc+xml      onepkg = application/onenote      onetmp = application/onenote      onetoc = application/onenote      onetoc2 = application/onenote      opf = application/oebps-package+xml      opml = text/x-opml      oprc = application/vnd.palm      org = application/vnd.lotus-organizer      osf = application/vnd.yamaha.openscoreformat      osfpvg = application/vnd.yamaha.openscoreformat.osfpvg+xml      otc = application/vnd.oasis.opendocument.chart-template      otf = application/x-font-otf      otg = application/vnd.oasis.opendocument.graphics-template      oth = application/vnd.oasis.opendocument.text-web      oti = application/vnd.oasis.opendocument.image-template      otp = application/vnd.oasis.opendocument.presentation-template      ots = application/vnd.oasis.opendocument.spreadsheet-template      ott = application/vnd.oasis.opendocument.text-template      oxps = application/oxps      oxt = application/vnd.openofficeorg.extension      p = text/x-pascal      p10 = application/pkcs10      p12 = application/x-pkcs12      p7b = application/x-pkcs7-certificates      p7c = application/pkcs7-mime      p7m = application/pkcs7-mime      p7r = application/x-pkcs7-certreqresp      p7s = application/pkcs7-signature      p8 = application/pkcs8      pas = text/x-pascal      paw = application/vnd.pawaafile      pbd = application/vnd.powerbuilder6      pbm = image/x-portable-bitmap      pcap = application/vnd.tcpdump.pcap      pcf = application/x-font-pcf      pcl = application/vnd.hp-pcl      pclxl = application/vnd.hp-pclxl      pct = image/pict      pct = image/x-pict      pcurl = application/vnd.curl.pcurl      pcx = image/x-pcx      pdb = application/vnd.palm      pdf = application/pdf      pfa = application/x-font-type1      pfb = application/x-font-type1      pfm = application/x-font-type1      pfr = application/font-tdpfr      pfx = application/x-pkcs12      pgm = image/x-portable-graymap      pgn = application/x-chess-pgn      pgp = application/pgp-encrypted      pic = image/pict      pic = image/x-pict      pict = image/pict      pkg = application/octet-stream      pki = application/pkixcmp      pkipath = application/pkix-pkipath      plb = application/vnd.3gpp.pic-bw-large      plc = application/vnd.mobius.plc      plf = application/vnd.pocketlearn      pls = application/pls+xml      pml = application/vnd.ctc-posml      png = image/png      pnm = image/x-portable-anymap      pnt = image/x-macpaint      pntg = image/x-macpaint      portpkg = application/vnd.macports.portpkg      pot = application/vnd.ms-powerpoint      potm = application/vnd.ms-powerpoint.template.macroenabled.12      potx = application/vnd.openxmlformats-officedocument.presentationml.template      ppam = application/vnd.ms-powerpoint.addin.macroenabled.12      ppd = application/vnd.cups-ppd      ppm = image/x-portable-pixmap      pps = application/vnd.ms-powerpoint      ppsm = application/vnd.ms-powerpoint.slideshow.macroenabled.12      ppsx = application/vnd.openxmlformats-officedocument.presentationml.slideshow      ppt = application/vnd.ms-powerpoint      pptm = application/vnd.ms-powerpoint.presentation.macroenabled.12      pptx = application/vnd.openxmlformats-officedocument.presentationml.presentation      pqa = application/vnd.palm      prc = application/x-mobipocket-ebook      pre = application/vnd.lotus-freelance      prf = application/pics-rules      ps = application/postscript      psb = application/vnd.3gpp.pic-bw-small      psd = image/vnd.adobe.photoshop      psf = application/x-font-linux-psf      pskcxml = application/pskc+xml      ptid = application/vnd.pvi.ptid1      pub = application/x-mspublisher      pvb = application/vnd.3gpp.pic-bw-var      pwn = application/vnd.3m.post-it-notes      pya = audio/vnd.ms-playready.media.pya      pyv = video/vnd.ms-playready.media.pyv      qam = application/vnd.epson.quickanime      qbo = application/vnd.intu.qbo      qfx = application/vnd.intu.qfx      qps = application/vnd.publishare-delta-tree      qt = video/quicktime      qti = image/x-quicktime      qtif = image/x-quicktime      qwd = application/vnd.quark.quarkxpress      qwt = application/vnd.quark.quarkxpress      qxb = application/vnd.quark.quarkxpress      qxd = application/vnd.quark.quarkxpress      qxl = application/vnd.quark.quarkxpress      qxt = application/vnd.quark.quarkxpress      ra = audio/x-pn-realaudio      ram = audio/x-pn-realaudio      rar = application/x-rar-compressed      ras = image/x-cmu-raster      rcprofile = application/vnd.ipunplugged.rcprofile      rdf = application/rdf+xml      rdz = application/vnd.data-vision.rdz      rep = application/vnd.businessobjects      res = application/x-dtbresource+xml      rgb = image/x-rgb      rif = application/reginfo+xml      rip = audio/vnd.rip      ris = application/x-research-info-systems      rl = application/resource-lists+xml      rlc = image/vnd.fujixerox.edmics-rlc      rld = application/resource-lists-diff+xml      rm = application/vnd.rn-realmedia      rmi = audio/midi      rmp = audio/x-pn-realaudio-plugin      rms = application/vnd.jcp.javame.midlet-rms      rmvb = application/vnd.rn-realmedia-vbr      rnc = application/relax-ng-compact-syntax      roa = application/rpki-roa      roff = text/troff      rp9 = application/vnd.cloanto.rp9      rpss = application/vnd.nokia.radio-presets      rpst = application/vnd.nokia.radio-preset      rq = application/sparql-query      rs = application/rls-services+xml      rsd = application/rsd+xml      rss = application/rss+xml      rtf = application/rtf      rtx = text/richtext      s = text/x-asm      s3m = audio/s3m      saf = application/vnd.yamaha.smaf-audio      sbml = application/sbml+xml      sc = application/vnd.ibm.secure-container      scd = application/x-msschedule      scm = application/vnd.lotus-screencam      scq = application/scvp-cv-request      scs = application/scvp-cv-response      scurl = text/vnd.curl.scurl      sda = application/vnd.stardivision.draw      sdc = application/vnd.stardivision.calc      sdd = application/vnd.stardivision.impress      sdkd = application/vnd.solent.sdkm+xml      sdkm = application/vnd.solent.sdkm+xml      sdp = application/sdp      sdw = application/vnd.stardivision.writer      see = application/vnd.seemail      seed = application/vnd.fdsn.seed      sema = application/vnd.sema      semd = application/vnd.semd      semf = application/vnd.semf      ser = application/java-serialized-object      setpay = application/set-payment-initiation      setreg = application/set-registration-initiation      sfs = application/vnd.spotfire.sfs      sfv = text/x-sfv      sgi = image/sgi      sgl = application/vnd.stardivision.writer-global      sgm = text/sgml      sgml = text/sgml      sh = application/x-sh      shar = application/x-shar      shf = application/shf+xml      sid = image/x-mrsid-image      sig = application/pgp-signature      sil = audio/silk      silo = model/mesh      sis = application/vnd.symbian.install      sisx = application/vnd.symbian.install      sit = application/x-stuffit      sitx = application/x-stuffitx      skd = application/vnd.koan      skm = application/vnd.koan      skp = application/vnd.koan      skt = application/vnd.koan      sldm = application/vnd.ms-powerpoint.slide.macroenabled.12      sldx = application/vnd.openxmlformats-officedocument.presentationml.slide      slt = application/vnd.epson.salt      sm = application/vnd.stepmania.stepchart      smf = application/vnd.stardivision.math      smi = application/smil+xml      smil = application/smil+xml      smv = video/x-smv      smzip = application/vnd.stepmania.package      snd = audio/basic      snf = application/x-font-snf      so = application/octet-stream      spc = application/x-pkcs7-certificates      spf = application/vnd.yamaha.smaf-phrase      spl = application/x-futuresplash      spot = text/vnd.in3d.spot      spp = application/scvp-vp-response      spq = application/scvp-vp-request      spx = audio/ogg      sql = application/x-sql      src = application/x-wais-source      srt = application/x-subrip      sru = application/sru+xml      srx = application/sparql-results+xml      ssdl = application/ssdl+xml      sse = application/vnd.kodak-descriptor      ssf = application/vnd.epson.ssf      ssml = application/ssml+xml      st = application/vnd.sailingtracker.track      stc = application/vnd.sun.xml.calc.template      std = application/vnd.sun.xml.draw.template      stf = application/vnd.wt.stf      sti = application/vnd.sun.xml.impress.template      stk = application/hyperstudio      stl = application/vnd.ms-pki.stl      str = application/vnd.pg.format      stw = application/vnd.sun.xml.writer.template      sub = image/vnd.dvb.subtitle      sub = text/vnd.dvb.subtitle      sus = application/vnd.sus-calendar      susp = application/vnd.sus-calendar      sv4cpio = application/x-sv4cpio      sv4crc = application/x-sv4crc      svc = application/vnd.dvb.service      svd = application/vnd.svd      svg = image/svg+xml      svgz = image/svg+xml      swa = application/x-director      swf = application/x-shockwave-flash      swi = application/vnd.aristanetworks.swi      sxc = application/vnd.sun.xml.calc      sxd = application/vnd.sun.xml.draw      sxg = application/vnd.sun.xml.writer.global      sxi = application/vnd.sun.xml.impress      sxm = application/vnd.sun.xml.math      sxw = application/vnd.sun.xml.writer      t = text/troff      t3 = application/x-t3vm-image      taglet = application/vnd.mynfc      tao = application/vnd.tao.intent-module-archive      tar = application/x-tar      tcap = application/vnd.3gpp2.tcap      tcl = application/x-tcl      teacher = application/vnd.smart.teacher      tei = application/tei+xml      teicorpus = application/tei+xml      tex = application/x-tex      texi = application/x-texinfo      texinfo = application/x-texinfo      text = text/plain      tfi = application/thraud+xml      tfm = application/x-tex-tfm      tga = image/x-tga      thmx = application/vnd.ms-officetheme      tif = image/tiff      tiff = image/tiff      tmo = application/vnd.tmobile-livetv      torrent = application/x-bittorrent      tpl = application/vnd.groove-tool-template      tpt = application/vnd.trid.tpt      tr = text/troff      tra = application/vnd.trueapp      trm = application/x-msterminal      ts = video/mp2t      tsd = application/timestamped-data      tsv = text/tab-separated-values      ttc = application/x-font-ttf      ttf = application/x-font-ttf      ttl = text/turtle      twd = application/vnd.simtech-mindmapper      twds = application/vnd.simtech-mindmapper      txd = application/vnd.genomatix.tuxedo      txf = application/vnd.mobius.txf      txt = text/plain      u32 = application/x-authorware-bin      udeb = application/x-debian-package      ufd = application/vnd.ufdl      ufdl = application/vnd.ufdl      ulx = application/x-glulx      umj = application/vnd.umajin      unityweb = application/vnd.unity      uoml = application/vnd.uoml+xml      uri = text/uri-list      uris = text/uri-list      urls = text/uri-list      ustar = application/x-ustar      utz = application/vnd.uiq.theme      uu = text/x-uuencode      uva = audio/vnd.dece.audio      uvd = application/vnd.dece.data      uvf = application/vnd.dece.data      uvg = image/vnd.dece.graphic      uvh = video/vnd.dece.hd      uvi = image/vnd.dece.graphic      uvm = video/vnd.dece.mobile      uvp = video/vnd.dece.pd      uvs = video/vnd.dece.sd      uvt = application/vnd.dece.ttml+xml      uvu = video/vnd.uvvu.mp4      uvv = video/vnd.dece.video      uvva = audio/vnd.dece.audio      uvvd = application/vnd.dece.data      uvvf = application/vnd.dece.data      uvvg = image/vnd.dece.graphic      uvvh = video/vnd.dece.hd      uvvi = image/vnd.dece.graphic      uvvm = video/vnd.dece.mobile      uvvp = video/vnd.dece.pd      uvvs = video/vnd.dece.sd      uvvt = application/vnd.dece.ttml+xml      uvvu = video/vnd.uvvu.mp4      uvvv = video/vnd.dece.video      uvvx = application/vnd.dece.unspecified      uvvz = application/vnd.dece.zip      uvx = application/vnd.dece.unspecified      uvz = application/vnd.dece.zip      vcard = text/vcard      vcd = application/x-cdlink      vcf = text/x-vcard      vcg = application/vnd.groove-vcard      vcs = text/x-vcalendar      vcx = application/vnd.vcx      vis = application/vnd.visionary      viv = video/vnd.vivo      vob = video/x-ms-vob      vor = application/vnd.stardivision.writer      vox = application/x-authorware-bin      vrml = model/vrml      vsd = application/vnd.visio      vsf = application/vnd.vsf      vss = application/vnd.visio      vst = application/vnd.visio      vsw = application/vnd.visio      vtu = model/vnd.vtu      vxml = application/voicexml+xml      w3d = application/x-director      wad = application/x-doom      wav = audio/x-wav      wax = audio/x-ms-wax      wbmp = image/vnd.wap.wbmp      wbs = application/vnd.criticaltools.wbs+xml      wbxml = application/vnd.wap.wbxml      wcm = application/vnd.ms-works      wdb = application/vnd.ms-works      wdp = image/vnd.ms-photo      weba = audio/webm      webm = video/webm      webp = image/webp      wg = application/vnd.pmi.widget      wgt = application/widget      wks = application/vnd.ms-works      wm = video/x-ms-wm      wma = audio/x-ms-wma      wmd = application/x-ms-wmd      wmf = application/x-msmetafile      wml = text/vnd.wap.wml      wmlc = application/vnd.wap.wmlc      wmls = text/vnd.wap.wmlscript      wmlsc = application/vnd.wap.wmlscriptc      wmv = video/x-ms-wmv      wmx = video/x-ms-wmx      wmz = application/x-ms-wmz      wmz = application/x-msmetafile      woff = application/x-font-woff      wpd = application/vnd.wordperfect      wpl = application/vnd.ms-wpl      wps = application/vnd.ms-works      wqd = application/vnd.wqd      wri = application/x-mswrite      wrl = model/vrml      wsdl = application/wsdl+xml      wspolicy = application/wspolicy+xml      wtb = application/vnd.webturbo      wvx = video/x-ms-wvx      x32 = application/x-authorware-bin      x3d = model/x3d+xml      x3db = model/x3d+binary      x3dbz = model/x3d+binary      x3dv = model/x3d+vrml      x3dvz = model/x3d+vrml      x3dz = model/x3d+xml      xaml = application/xaml+xml      xap = application/x-silverlight-app      xar = application/vnd.xara      xbap = application/x-ms-xbap      xbd = application/vnd.fujixerox.docuworks.binder      xbm = image/x-xbitmap      xdf = application/xcap-diff+xml      xdm = application/vnd.syncml.dm+xml      xdp = application/vnd.adobe.xdp+xml      xdssc = application/dssc+xml      xdw = application/vnd.fujixerox.docuworks      xenc = application/xenc+xml      xer = application/patch-ops-error+xml      xfdf = application/vnd.adobe.xfdf      xfdl = application/vnd.xfdl      xht = application/xhtml+xml      xhtml = application/xhtml+xml      xhvml = application/xv+xml      xif = image/vnd.xiff      xla = application/vnd.ms-excel      xlam = application/vnd.ms-excel.addin.macroenabled.12      xlc = application/vnd.ms-excel      xlf = application/x-xliff+xml      xlm = application/vnd.ms-excel      xls = application/vnd.ms-excel      xlsb = application/vnd.ms-excel.sheet.binary.macroenabled.12      xlsm = application/vnd.ms-excel.sheet.macroenabled.12      xlsx = application/vnd.openxmlformats-officedocument.spreadsheetml.sheet      xlt = application/vnd.ms-excel      xltm = application/vnd.ms-excel.template.macroenabled.12      xltx = application/vnd.openxmlformats-officedocument.spreadsheetml.template      xlw = application/vnd.ms-excel      xm = audio/xm      xml = application/xml      xo = application/vnd.olpc-sugar      xop = application/xop+xml      xpi = application/x-xpinstall      xpl = application/xproc+xml      xpm = image/x-xpixmap      xpr = application/vnd.is-xpr      xps = application/vnd.ms-xpsdocument      xpw = application/vnd.intercon.formnet      xpx = application/vnd.intercon.formnet      xsl = application/xml      xslt = application/xslt+xml      xsm = application/vnd.syncml+xml      xspf = application/xspf+xml      xul = application/vnd.mozilla.xul+xml      xvm = application/xv+xml      xvml = application/xv+xml      xwd = image/x-xwindowdump      xyz = chemical/x-xyz      xz = application/x-xz      yang = application/yang      yin = application/yin+xml      z1 = application/x-zmachine      z2 = application/x-zmachine      z3 = application/x-zmachine      z4 = application/x-zmachine      z5 = application/x-zmachine      z6 = application/x-zmachine      z7 = application/x-zmachine      z8 = application/x-zmachine      zaz = application/vnd.zzazz.deck+xml      zip = application/zip      zir = application/vnd.zul      zirz = application/vnd.zul      zmm = application/vnd.handheld-entertainment+xml   }}