It doesn't happen every time, but often. It's intermittent. Even within a single job some writes succeed, and then another one fails.
```
Tue Feb 10 5:58:38 UTC 2015
integration-slave1006
build276
SqlBagOStuff::set/single-row
5
database is locked
REPLACE INTO objectcache (keyname,value,exptime) VALUES ('build276:resourceloader:modulemodifiedhash:mediawiki.language.data:ade3504093df2f931359f1c5028d085d',x'15cacb09c0200c00d05d3241cc879a388d54450f4221bd95ee5efaceaf3af9132e0eb3c68412cee4505b674541e336681827561be954a4dc306bfb9f39dc6bf7b8ebbea02c4f42ac7258cae5fd00','20380119031407')
```
```
DatabaseBase::query: Writes done: REPLACE INTO objectcache (keyname,value,exptime) VALUES ('X')
SQL ERROR: database is locked
[SQLBagOStuff] DBError: A database error has occurred. Did you forget to run maintenance/update.php after upgrading? See: https://www.mediawiki.org/wiki/Manual:Upgrading#Run_the_update_script
Query: REPLACE INTO objectcache (keyname,value,exptime) VALUES ('build276:resourceloader:modulemodifiedhash:mediawiki.language.data:ade3504093df2f931359f1c5028d085d',x'15cacb09c0200c00d05d3241cc879a388d54450f4221bd95ee5efaceaf3af9132e0eb3c68412cee4505b674541e336681827561be954a4dc306bfb9f39dc6bf7b8ebbea02c4f42ac7258cae5fd00','20380119031407')
Function: SqlBagOStuff::set/single-row
Error: 5 database is locked
[SQLBagOStuff] SqlBagOStuff::handleWriteError: ignoring query error
LoadBalancer::getConnection: using server for group
LoadBalancer::getConnection: using server for group
DatabaseBase::query: Writes done: PRAGMA case_sensitive_like = N
Connected to database 0 at
DatabaseBase::query: Writes done: REPLACE INTO objectcache (keyname,value,exptime) VALUES ('X')
SQL ERROR (ignored): database is locked
DatabaseBase::query: Writes done: DELETE FROM l10n_cache WHERE lc_lang = 'X'
LoadBalancer::getConnection: using server for group
LoadBalancer::getConnection: using server for group
LoadBalancer::getConnection: using server for group
LocalisationCache::isExpired(ar): cache missing, need to make one
DatabaseBase::query: Writes done: INSERT INTO l10n_cache (lc_lang,lc_key,lc_value) VALUES ('X')
DatabaseBase::query: Writes done: INSERT INTO l10n_cache (lc_lang,lc_key,lc_value) VALUES ('X')
LocalisationCache::recache: got localisation for ar from source
DatabaseBase::query: Writes done: INSERT INTO l10n_cache (lc_lang,lc_key,lc_value) VALUES ('X')
DatabaseBase::query: Writes done: INSERT INTO l10n_cache (lc_lang,lc_key,lc_value) VALUES ('X')
```