获得502,504高CPU使用率。 Wordpress仪表板太慢了

Question

I've been getting this error when logged in users try to create new posts, save new posts

 upstream timed out (110: Connection timed out) while reading response header from upstream, client: 127.0.0.1, server: www.website.com, request: "POST /wp-admin/admin-ajax.php HTTP/1.1", upstream: "fastcgi://127.0.0.1:9000", host: "www.website.com", referrer: "http://www.website.com/wp-admin/post-new.php"

After racking my brains and trying almost everything I can find online, I see that mysql is taking too much cpu and it's in sleep state:

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND
 1165 mysql     20   0 6710000 392500   7704 S 538.4  1.2 429:15.23 mysqld
 8538 nginx     20   0 1011120 767704  28384 R  96.5  2.3   0:38.88 php5-fpm
 8631 nginx     20   0 1008752 765972  28516 S  64.8  2.3   0:41.22 php5-fpm
 8933 nginx     20   0  342324 105612  27164 S  14.9  0.3   1:12.39 php5-fpm
 8282 nginx     20   0  284956  47704  28680 S  11.9  0.1   0:22.16 php5-fpm
 8696 nginx     20   0  285428  48580  27180 S  11.9  0.1   1:06.20 php5-fpm
 7893 nginx     20   0  276920  39524  28536 S   9.9  0.1   0:29.77 php5-fpm
 8839 nginx     20   0  284152  47772  27736 S   9.9  0.1   0:07.72 php5-fpm
 1239 nobody    20   0 1562720 388788  83312 S   8.9  1.2   9:01.75 varnishd
 9176 nginx     20   0  282612  43620  24884 S   8.9  0.1   0:00.95 php5-fpm
 7781 nginx     20   0  287504  50200  28740 S   8.3  0.2   0:39.74 php5-fpm
 8905 nginx     20   0  283128  47108  27852 S   8.3  0.1   0:05.36 php5-fpm
 7913 nginx     20   0  284684  47424  28672 S   7.6  0.1   0:29.60 php5-fpm
 8728 nginx     20   0  587692 350692  27232 S   7.6  1.1   1:06.50 php5-fpm
 8750 nginx     20   0  282872  46640  27644 S   7.6  0.1   0:08.28 php5-fpm
 8277 nginx     20   0  313220  75636  28504 S   6.9  0.2   1:19.49 php5-fpm
 8675 nginx     20   0  284944  47280  28268 S   6.9  0.1   0:09.52 php5-fpm

How to solve this issue?

I'm not able to save anything or create new posts, the dashboard is horribly slow. Please guide me.

UPDATE: I decided to check the wait_timeout and this is what I got:

SHOW SESSION VARIABLES LIKE "%wait%";
+---------------------------------------------------+----------+
| Variable_name                                     | Value    |
+---------------------------------------------------+----------+
| innodb_lock_wait_timeout                          | 50       |
| innodb_spin_wait_delay                            | 6        |
| lock_wait_timeout                                 | 31536000 |
| performance_schema_events_waits_history_long_size | 10000    |
| performance_schema_events_waits_history_size      | 10       |
| wait_timeout                                      | 28800    |
+---------------------------------------------------+----------+

Is it just me or the wait_timeout of 28800 is insanely high? Can this be the problem?

Answer 1

first and most important question - do you have installed cache plugin (if cache is configured then data should be pulled from cache, not from db)