below apache2ctl status with almost no users online.
For over 5 years we (cloud ERP supplier) deploy instances on Google Cloud with Apache with mod_perl.
This week our largest server became slow and unresponsive. No idle workers were available. It turned out increasing both MaxRequestWorkers and ServerLimit to 400 from 150 in mpm_prefork.conf got our server back fast.
I’m wondering why many requests stay in "R" Reading Request, at least 10 times more requests then actually should be.
We did further checking, DoS does not seem to be the issue, as also other servers – in different clouds as ASW or Alibaba – we notice the same ratio of 10 between requests actually being processed (R/W/K) and requests that stay in Reading mode.
What could cause this?
sudo /usr/sbin/apache2ctl status Apache Server Status for localhost (via 127.0.0.1)
Server Version: Apache/2.4.7 (Ubuntu) PHP/5.5.9-1ubuntu4.29 OpenSSL/1.0.1f mod_perl/2.0.8 Perl/v5.18.2 Server MPM: prefork Server Built: Apr 3 2019 18:04:25
Current Time: Saturday, 29-Feb-2020 10:15:35 CET Restart Time: Thursday, 27-Feb-2020 09:45:48 CET Parent Server Config. Generation: 1 Parent Server MPM Generation: 0 Server uptime: 2 days 29 minutes 47 seconds Server load: 0.75 0.77 0.75 Total accesses: 1581181 - Total Traffic: 8.6 GB CPU Usage: u30.32 s9.64 cu0 cs0 - .0229% CPU load 9.06 requests/sec - 51.5 kB/second - 5.7 kB/request 96 requests currently being processed, 9 idle workers
RRKRRRK_RKRKKRRRRRK_RRRRKRCK_RRRC_CKK_KCRKCRK_RCR__CKKCCRCRRRRRR RRRRR.RRRKRRRKRRR_RR..R.K.RCRKR.CKK.RRKKR.W.RRKR.....RR......... ................................................................ ................................................................ ................................................................ ................................................................ ................
Scoreboard Key: "_" Waiting for Connection, "S" Starting up, "R" Reading Request, "W" Sending Reply, "K" Keepalive (read), "D" DNS Lookup, "C" Closing connection, "L" Logging, "G" Gracefully finishing, "I" Idle cleanup of worker, "." Open slot with no current process