{"id":333,"date":"2009-03-15T13:49:28","date_gmt":"2009-03-15T10:49:28","guid":{"rendered":"http:\/\/www.void.gr\/kargig\/blog\/?p=333"},"modified":"2009-05-03T13:13:59","modified_gmt":"2009-05-03T10:13:59","slug":"how-much-can-misconfigured-wordpress-plugins-stall-your-servers-performance","status":"publish","type":"post","link":"https:\/\/www.void.gr\/kargig\/blog\/2009\/03\/15\/how-much-can-misconfigured-wordpress-plugins-stall-your-servers-performance\/","title":{"rendered":"How much can misconfigured wordpress plugins stall your server’s performance"},"content":{"rendered":"

A couple of days ago I’ve met a guy who has a high traffic blog about tech stuff. The guy was telling me that he has hosting problems and that his blog is getting slower and slower by the day. I’ve offered to help him by providing hosting for him in one of the servers that I administer. After making the transition from his old hosting to my server, which was not an easy thing to do due to latin1 to utf8 conversions that had to be made – it deserves a post of it’s own, I started to notice increased load on my server. Sure his blog had heavy traffic…but could it be that bad ?
\n
\nThe first thing I noticed was that the disk usage was raising FAST.
\n\"server-df-day\"<\/a><\/p>\n

Since there was no heavy network traffic the data must have been created internally by the server. I started checking on the \/var\/log\/ directory.
\n# du -sh \/var\/log\/
\n4.6G \/var\/log\/<\/code>
\nThat needed further investigation for sure!
\n# du --max-depth=1 -h \/var\/log\/
\n[..snip..]
\n8.0K \/var\/log\/postgresql
\n4.6G \/var\/log\/mysql
\n12K \/var\/log\/fsck
\n[..snip..]
\n4.6G \/var\/log\/<\/code>
\nOK…the culprit was mysql for a reason. The directory mostly contained mysql binary logs.
\n# ls -Fla \/var\/log\/mysql\/ | grep mysql-bin | wc -l
\n58
\n# ls -Fla \/var\/log\/mysql\/ | grep mysql-bin | grep 03-14| wc -l
\n46
\n<\/code>
\nOut of the 58 binlogs, 46 were produced on the day of the transition. While the previous dates had binlogs of around 30-40Mb, the day of the transition had 46 binlogs of around 100Mb each! That’s 4.6Gb vs 40Mb for just one day!
\nI’ve opened up a few of those using mysql: # mysql -u root -p
\nSHOW BINLOG EVENTS IN 'mysql-bin.000337';
\n<\/code>
\nThe binlogs were full of some wordpress queries by the newly installed blog.<\/p>\n

I then asked for a wordpress admin account on the blog to check on the plugins. I found a lot of plugins installed. Two of those were WP-Cache<\/a> and DB-Cache<\/a>.
\nI started checking on WP-Cache. When I went to Settings->WP-Cache, it complained that it was misconfigured. It couldn’t create the cache files due to wrong permissions on some directories. So I changed the proper permissions and I could immediately see a difference on server load and on blog loading time. The blog took over 2.5 seconds to load when WP-Cache was misconfigured but it could now load in under 2 seconds. Still the mysql binlogs continued to increase in size very very fast.
\nDB-Cache on the other hand did not complain about anything when I went to Settings->DB-Cache. Only when I tried changing some settings it notified me that there was again a permissions’ problem. Fixing that started showing again some results. Blog’s load time fell down to 1.5-1.7 seconds. There were also less queries on the binlogs but still there were many. Many of those looked like:
\nUPDATE wp_options SET option_value = 'O:8:\\\"stdClass\\\":3:{s:7:\\\"updates\\\";a:1:{
\ni:0;O:8:\\\"stdClass\\\":5:{s:8:\\\"response\\\";s:7:\\\"upgrade\\\";s:3:\\\"url\\\";s:30:\\\"http:\/\/wordpress.org\/download\/\\\";s:7:\\\"package\\\";s:40:\\\"
\nhttp:\/\/wordpress.org\/wordpress-2.7.1.zip\\\";s:7:\\\"current\\\";s:5:\\\"2.7.1\\\";s:6:\\\"locale\\\";s:5:\\\"en_US\\\";}}s:12:\\\"last_checked\\\";i:1237
\n062227;s:15:\\\"version_checked\\\";s:3:\\\"abc\\\";}' WHERE option_name = 'update_core'<\/code>
\nI have no idea why wordpress with db-cache keeps doing those queries when DB-cache is enabled.<\/p>\n

Anyway, I disabled DB-Cache so the blog could only rely on my own cache settings for mysqld. The results were magnificent. Blog load time reduced to 1.0-1.2 seconds!! Mysql got a boost on cached queries and server load avg is also very low again.<\/p>\n

\"server-mysql_queries-day\"<\/a>
\n(ignore the spike at the end and notice the difference that happens sometime around saturday evening when the cached hits, purple, surpass the select, green)<\/p>\n

\"server-load-day\"<\/a><\/p>\n

Everybody is happy, client has a fast blog and I’ve got a very responsive and fast server \ud83d\ude42<\/p>\n","protected":false},"excerpt":{"rendered":"

A couple of days ago I’ve met a guy who has a high traffic blog about tech stuff. The guy was telling me that he has hosting problems and that his blog is getting slower and slower by the day. I’ve offered to help him by providing hosting for him in one of the servers […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"ep_exclude_from_search":false,"footnotes":""},"categories":[3],"tags":[20,17,595,19,16,18],"class_list":["post-333","post","type-post","status-publish","format-standard","hentry","category-linux","tag-caching","tag-db-cache","tag-linux","tag-mysql","tag-wordpress","tag-wp-cache"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t