The job https://integration.wikimedia.org/ci/job/beta-scap-eqiad/ takes a while, notably when generating the cache_git_info:
00:00:08.393 19:39:20 Started cache_git_info 00:12:20.924 19:51:33 Finished cache_git_info (duration: 12m 12s)
12 minutes :(
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Takes a while on beta because of all the extensions (plus disks are slower than in production where it takes like 20 seconds). IIRC we haven't done much to parallelize any of this, it serially walks the extensions directory. There are probably some easy wins here, but, again, it's been a beta-only problem so it hasn't been a high priority.
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I gave it a quick try on deployment-deploy01 reproducing scap.tasks.cache_git_info(). Namely getting extensions and skins git information with scap.git.info and writing the json to a dummy file take roughly 40 seconds:
/home/hashar/scap_git.py
#!/usr/bin/python import json from scap.git import info as git_info from scap.utils import iterate_subdirectories for kind in ['extensions', 'skins']: for stuff in iterate_subdirectories('/srv/mediawiki-staging/php-master/%s' % kind): print('Stuff: %s' % stuff) info = git_info(stuff) with open('/tmp/foo.json', 'w') as f: json.dump(info, f)
$ time python scap_git.py real 0m40.602s user 0m13.600s sys 0m26.824s
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I ended up manually hacking scap on deployment-deploy01 https://integration.wikimedia.org/ci/job/beta-scap-eqiad/222901/console:
00:00:06.979 09:11:21 cache_git_info( version=master ) wikidb is dewiktionary 00:00:07.705 09:11:22 Writing cache file /srv/mediawiki-staging/php-master/cache/gitinfo/info.json 00:00:08.447 09:11:23 Writing cache file /srv/mediawiki-staging/php-master/cache/gitinfo/info-extensions-WikibaseQualityExternalValidation.json 00:00:09.177 09:11:23 Writing cache file /srv/mediawiki-staging/php-master/cache/gitinfo/info-extensions-SubpageFun.json 00:00:09.934 09:11:24 Writing cache file /srv/mediawiki-staging/php-master/cache/gitinfo/info-extensions-Ads.json 00:00:10.697 09:11:25 Writing cache file /srv/mediawiki-staging/php-master/cache/gitinfo/info-extensions-HierarchyBuilder.json 00:00:11.434 09:11:26 Writing cache file /srv/mediawiki-staging/php-master/cache/gitinfo/info-extensions-FixedHeaderTable.json ... 00:12:30.765 09:23:45 Writing cache file /srv/mediawiki-staging/php-master/cache/gitinfo/info-skins-Slate.json 00:12:31.562 09:23:46 Writing cache file /srv/mediawiki-staging/php-master/cache/gitinfo/info-skins-Refreshed.json 00:12:31.565 09:23:46 Finished cache_git_info (duration: 12m 24s)
Using iwatch shows that is quite slow:
[24/Sep/2018 09:17:51] IN_MODIFY ./info-extensions-ExtensionDistributor.json [24/Sep/2018 09:17:51] IN_OPEN ./info-extensions-ExtensionDistributor.json [24/Sep/2018 09:17:51] IN_MODIFY ./info-extensions-ExtensionDistributor.json [24/Sep/2018 09:17:51] IN_CLOSE_WRITE ./info-extensions-ExtensionDistributor.json [24/Sep/2018 09:17:51] * ./info-extensions-ExtensionDistributor.json is closed [24/Sep/2018 09:17:52] IN_MODIFY ./info-extensions-WikiLabels.json [24/Sep/2018 09:17:52] IN_OPEN ./info-extensions-WikiLabels.json [24/Sep/2018 09:17:52] IN_MODIFY ./info-extensions-WikiLabels.json [24/Sep/2018 09:17:52] IN_CLOSE_WRITE ./info-extensions-WikiLabels.json [24/Sep/2018 09:17:52] * ./info-extensions-WikiLabels.json is closed [24/Sep/2018 09:17:53] IN_MODIFY ./info-extensions-SacredText.json [24/Sep/2018 09:17:53] IN_OPEN ./info-extensions-SacredText.json [24/Sep/2018 09:17:53] IN_MODIFY ./info-extensions-SacredText.json [24/Sep/2018 09:17:53] IN_CLOSE_WRITE ./info-extensions-SacredText.json [24/Sep/2018 09:17:53] * ./info-extensions-SacredText.json is closed [24/Sep/2018 09:17:53] IN_MODIFY ./info-extensions-BoilerPlate.json [24/Sep/2018 09:17:53] IN_OPEN ./info-extensions-BoilerPlate.json [24/Sep/2018 09:17:53] IN_MODIFY ./info-extensions-BoilerPlate.json [24/Sep/2018 09:17:53] IN_CLOSE_WRITE ./info-extensions-BoilerPlate.json [24/Sep/2018 09:17:53] * ./info-extensions-BoilerPlate.json is closed
Then strace shows a spam of close(x) = -1 EBADF (Bad file descriptor), that might be a reason for the slow down. That also happens with my dummy scap_git.py script though it is still WAY faster.
Maybe that is related to writes to /srv/mediawiki-staging/php-master/cache/gitinfo being slow.
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Mentioned in SAL (#wikimedia-releng) [2018-09-24T09:24:08Z] <hashar> Live hacked scap code on deployment-deploy01 for T204762 and reverted hack changes
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Mentioned in SAL (#wikimedia-releng) [2018-09-24T09:51:48Z] <hashar> deployment-deploy01 : backed up /srv/mediawiki-staging/php-master/cache/gitinfo and created a new. Its size of 69632 bytes might cause slow writes?? | T204762
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The spam of close(x) = -1 EBADF (Bad file descriptor) comes from a call to os.closerange
scap/sh.py
1679 class OProc(object): 1691 def __init__(self, command, parent_log, cmd, stdin, stdout, stderr, 1862 self.pid = os.fork() 1863 1864 # child 1865 if self.pid == 0: # pragma: no cover 1955 # don't inherit file descriptors 1956 max_fd = resource.getrlimit(resource.RLIMIT_NOFILE)[0] 1957 os.closerange(3, max_fd)
That is https://amoffat.github.io/sh/ which looks like syntaxic sugar to run shell commands so one can sh.git.show("HEAD"). It seems to reimplement subprocess methods, which is probably not a good idea :] But that is orthogonal to the disk slowness.
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Even funnier, I wanted to trace the execution of scap sync using the python trace module. The git caching took less than a minute!
$ ssh deployment-deploy01.deployment-prep.eqiad.wmflabs $ sudo su - jenkins-deploy $ cd /srv/mediawiki-staging $ scap sync 10:44:34 Started scap: (no justification provided) ... 10:44:40 Started cache_git_info 10:45:35 Finished cache_git_info (duration: 00m 54s) ... 10:47:00 Finished scap: (no justification provided) (duration: 02m 26s)
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I wanted some historical build durations. I took the IRC logs from https://wm-bot.wmflabs.org/logs/%23wikimedia-releng/ and looked for the irc notification when beta-scap-eqiad is fixed.
| Date | Build # | Duration |
|---|---|---|
| 20180701 03:49:13 | #214047 | 5 min 18 sec |
| 20180704 05:37:09 | #214503 | 4 min 13 sec |
| 20180705 11:17:56 | #214593 | 4 min 8 sec |
| 20180707 03:56:23 | #214858 | 12 min |
| 20180717 23:29:25 | #216392 | 47 min |
| 20180719 21:28:19 | #216629 | 4 min 30 sec |
| 20180723 02:58:01 | #217108 | 4 min 18 sec |
| 20180824 22:43:06 | #220162 | 48 min |
| 20180827 21:44:55 | #220424 | 31 min |
| 20180828 21:13:24 | #220501 | 29 min |
| 20180829 12:42:51 | #220555 | 15 min |
| 20180830 22:49:50 | #220677 | 16 min |
| 20180902 13:33:44 | #220907 | 15 min |
| 20180903 08:15:54 | #220979 | 14 min |
| 20180904 03:39:51 | #221051 | 16 min |
| 20180904 17:43:15 | #221102 | 15 min |
| 20180905 17:10:59 | #221179 | 17 min |
| 20180906 08:21:04 | #221229 | 15 min |
| 20180907 21:19:51 | #221362 | 49 min |
| 20180913 14:38:40 | #221839 | 13 min |
| 20180914 11:51:19 | #221925 | 14 min |
| 20180914 14:38:12 | #221938 | 14 min |
| 20180914 21:36:33 | #221966 | 14 min |
| 20180916 17:55:32 | #222151 | 13 min |
| 20180916 22:26:51 | #222169 | 16 min |
| 20180920 01:47:10 | #222474 | 13 min |
| 20180920 11:17:15 | #222513 | 13 min |
| 20180921 01:39:15 | #222570 | 13 min |
| 20180922 18:21:48 | #222737 | 13 min |
| 20180923 15:36:11 | #222825 | 13 min |
| 20180924 02:47:59 | #222872 | 14 min |
| 20180924 08:39:05 | #222897 | 15 min |
| 20180924 16:37:12 | #222932 | 13 min |
| 20180925 06:38:30 | #222988 | 13 min |
| 20180925 10:57:25 | #223006 | 15 min |
| 20180925 11:16:23 | #223008 | 13 min |
There are holes in the data set, but July 23th 2018 and they are definitely slow since at least August 30th.
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If that is from scap, that might be one of:
- 35e4dc6ea8557bb0ba63ec7eacd7e7233a24cd7e - sync-wikiversion: don't overwrite AbstractSync
- 8bd680cf1a51c29ab355ad192d83924d5e0db1ab - Add --force to AbstractSync
f7cb839114333a5b00ed99f44f13fbfb64157857 from August 28th already notes that cache_git_info is slow on beta.
Or (most probably) it is entirely unrelated to scap itself.