[Spike] Try out hack (<?hh) for mediawiki-config
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	greg
	Mar 4 2015, 11:45 PM

Description

A fun hackathon project-level test to see what would be required.

NB: This is not a first step in a proposal to switch us wholly over to Hack.

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Status	Subtype	Assigned	Task
Declined		• demon	T91590 [Spike] Try out hack (<?hh) for mediawiki-config
Resolved		None	T86081 Complete the use of HHVM over Zend PHP on the Wikimedia cluster
Resolved		Joe	T86096 Switch HAT appservers to trusty's ICU (or newer)
Resolved		Joe	T78765 Convert jobrunners to HHVM
Resolved		Joe	T84842 Convert eqiad imagescalers to HHVM, Trusty
Resolved		tstarling	T91468 HHVM with FastCGI does not support streaming output
Resolved		Joe	T93194 Create an HHVM 3.6.0 package, adding Tim's streaming patch
Resolved		kaldari	T58041 updateCollation.php script prohibitively slow for very large wikis
Resolved		jcrespo	T130692 Add new indexes from eec016ece6d2b30addcdf3d3efcc2ba59b10e858 to production databases
Resolved		Volans	T128353 Switchover to new s3 master
Resolved	PRODUCTION ERROR	aaron	T126436 Spikes of mediawiki in read only for job runners after altering the s2 slaves topology
Invalid		None	T126632 Scap should restart job runners to pick up new config
Declined		ArielGlenn	T94277 Convert snapshot hosts to use HHVM and trusty
Resolved		ArielGlenn	T111586 Snapshot hosts need to be manually added to dataset1001's exports
Resolved		ori	T113932 HHVM does not recognize compress.bzip2 streams
Declined		None	T117534 DCAT-AP: XML produces invalid output with HHVM
Resolved		MoritzMuehlenhoff	T143648 Merge facebook/hhvm@9d2be6c30b into build of next hhvm release
Resolved		Joe	T87036 Convert work machines (tin, terbium) to Trusty and hhvm usage
Resolved		Joe	T116728 Reimage mw1152 as a terbium replacement
Resolved		Joe	T124024 Be able to switch programmatically between deployment servers in codfw and eqiad
Resolved		Andrew	T98813 Move wikitech (silver) to HHVM
Resolved		Joe	T104747 Convert tmh100[12] to HHVM and trusty
Duplicate		fgiunchedi	T107313 Backport ffmpeg 2.7.3 to Trusty
Resolved		• brooke	T69953 ogv transcodes have broken audio tracks with ffmpeg2theora 0.29 (Trusty upstream)
Resolved		• brooke	T103335 Investigate impact of switching from ffmpeg to libav (ffmpeg is not in Jessie)
Resolved		bd808	T110707 Upgrade Beta Cluster tmh* host(s) to HHVM and Trusty
Resolved		Joe	T113284 Frequent job timeouts on HHVM video scalers
Resolved		fgiunchedi	T146285 Switch mwscript from Zend PHP5 to default php alternative (e.g. HHVM or PHP7)
Resolved	PRODUCTION ERROR	EBernhardson	T132751 "Elastica: missing curl_init_pooled method" due to mwscript job running with PHP 5 on terbium
Resolved		Krenair	T125540 New version of File:Duniya Na Mane, 1937.webm
Resolved		None	T25748 Bad label on upload max filesize at upload page in spanish version
Resolved		hashar	T146286 mwscript on jessie mediawiki fails
Resolved		tstarling	T145819 Jobs invoking SiteConfiguration::getConfig cause HHVM to fail updating the bytecode cache due to being filesize limited to 512MBytes
Resolved		tstarling	T111441 SiteConfiguration::getConfig() does not work in Wikimedia production

Event Timeline

greg created this task.Mar 4 2015, 11:45 PM

greg assigned this task to • demon.

greg raised the priority of this task from to Lowest.

greg updated the task description. (Show Details)

greg added a project: Release-Engineering-Team.

greg subscribed.

Restricted Application added a subscriber: Aklapper. · View Herald TranscriptMar 4 2015, 11:45 PM

• demon added a project: Wikimedia-Hackathon-2015.Mar 4 2015, 11:46 PM

greg moved this task from Backlog to Hacking proposals on the Wikimedia-Hackathon-2015 board.Mar 4 2015, 11:46 PM

greg mentioned this in T92565: Release/QA tasks at the Wikimedia Hackathon 2015.Mar 12 2015, 9:16 PM

We'll have to turn it on first. I broke testwiki trying :p

Florian subscribed.May 18 2015, 1:10 PM

Did someone work on this project during Wikimedia-Hackathon-2015? If so, please update the task with the results. If not, please remove the label.

greg edited projects, added acl*sre-team; removed Wikimedia-Hackathon-2015.May 28 2015, 5:09 PM

greg set Security to None.

Don't want to lick this cookie too hard, haven't had time to play with it. We'll have to change some settings in HHVM (forgot which one) and scap & co will need updates to reflect the proper linter.

(Should we be linting with hhvm anyway? Hmm....)

We can't even consider this until the entire production MW server fleet is running on HHVM. This includes the misc servers such as tin and turbium. As Tim has pointed out before, it would be embarrassing if we couldn't run our own software. :)

Beyond that blocker, I guess I would be fine with the attempt but I'm not sure what concrete benefits we would hope to achieve beyond an "it didn't break" proof of concept. As far as I understand it, the primary benefits of Hack are the ability to provide stronger type hints for the JIT compiler and access to various async constructs developed uniquely for Facebook. Neither of these sounds like things that would be highly beneficial at the wiki farm config level but maybe I'm missing something.

bd808 added a subtask: T86081: Complete the use of HHVM over Zend PHP on the Wikimedia cluster.Jun 2 2015, 3:45 PM

Ricordisamoa awarded a token.Jun 2 2015, 4:21 PM

Ricordisamoa subscribed.

In T91590#1329608, @demon wrote:

(Should we be linting with hhvm anyway? Hmm....)

Once tin is upgraded to trusty php will point to hhvm and we'd be linting with HHVM. But until 5.3 is dead we should be linting with the lowest requirement.

Also HHVM's linter is significantly slower than PHP5: https://github.com/JakubOnderka/PHP-Parallel-Lint/issues/47

Krenair subscribed.Jun 2 2015, 11:23 PM

In T91590#1332329, @Legoktm wrote:

Also HHVM's linter is significantly slower than PHP5: https://github.com/JakubOnderka/PHP-Parallel-Lint/issues/47

This is a general consequence of HHVM and its JIT. HHVM will always be slower than PHP5 for short lived tasks due to the startup time costs of setting up the JIT system and recording bytecode in the sqlite bytecode cache.

In T91590#1332763, @bd808 wrote:

In T91590#1332329, @Legoktm wrote:

Also HHVM's linter is significantly slower than PHP5: https://github.com/JakubOnderka/PHP-Parallel-Lint/issues/47

This is a general consequence of HHVM and its JIT. HHVM will always be slower than PHP5 for short lived tasks due to the startup time costs of setting up the JIT system and recording bytecode in the sqlite bytecode cache.

Maybe a better first step is just adding HHVM linting to Jenkins? :)

jeremyb subscribed.Jun 30 2015, 5:44 AM

Restricted Application added a subscriber: Matanya. · View Herald TranscriptJun 30 2015, 5:44 AM

Krenair mentioned this in T98813: Move wikitech (silver) to HHVM.Jun 30 2015, 1:42 PM

Do we really want to vendor-lock us into HHVM? For what gain?

Do we really, really have a compelling reason to use hack in mediawiki-config? A performance gain?

In T91590#1517624, @Joe wrote:

Do we really want to vendor-lock us into HHVM? For what gain?

Do we really, really have a compelling reason to use hack in mediawiki-config? A performance gain?

I indirectly replied by editing the description to make it clear this isn't meant to be a backdoor to us using Hack. This is a fun hackathon idea (for Lyon) that didn't happen. Lowest priority for a reason :)

Maybe we should just close this task until we open up the discussion to migrate to Hack? Meanwhile, that is yet another opened bug adding overhead :(

In T91590#1525171, @hashar wrote:

Maybe we should just close this task until we open up the discussion to migrate to Hack? Meanwhile, that is yet another opened bug adding overhead :(

I'm fine with that if there's no plans to do anything with it. @demon?