Ticket #36 (assigned enhancement)

Opened 3 years ago

Last modified 10 months ago

fcgi remote backends intelligent availability check

Reported by: glen Assigned to: jan (accepted)
Priority: high Milestone: 1.4.20
Component: core Version: 1.3.11
Severity: normal Keywords:
Cc: arkadi@mebius.lv Blocking:
Need Feedback:

Description

say, i have configured three fcgi-handlers for one URI in lighttpd. if lighttpd, sees that fcgi backend is unavailable (say, connection refused), it marks it offline (fcgi server disabled). if in case all of them are disabled, it would be neccessary that the fcgi servers are instantly checked for availability again, without the existing timeout. since the servers might have returned. real case: i restarted fcgi backend daemons one by one. and i had to restart lighttpd to make it again serve fcgi requests.

my idea would be that the timeout for checking fcgi backend is lowered for fcgi server, if all of them are unavailable for same URI, and perhaps exponentally increased if the check of all fcgi servers fails (again). and of course initial first check must be done instantly (ie without timeout). and perhaps if the fcgi server becames available, the disabled-timeout is set back to default normal value.

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Change History

03/01/2005 05:03:57 PM changed by jan

  • status changed from new to assigned.
  • milestone set to lighttpd-1.4.0.

03/01/2005 05:04:13 PM changed by jan

  • severity changed from normal to enhancement.

03/20/2005 09:32:32 AM changed by arkadi@mebius.lv

Please also make #define FCGI_RETRY_TIMEOUT (5 * 60) configurable at least at global level. A short restart of manually spawned PHP processes after php.ini corrections leads to excessive vhost unavailability.

03/20/2005 09:38:35 AM changed by jan

FCGI_RETRY_TIMEOUT is already gone in svn.

12/05/2005 08:34:59 PM changed by glen@delfi.ee

until this above is not implemented, what about improving retry_timeout checks.

when one of the fcgi servers is out (connection refused). then webserver cycles such log entries every $FCGI_RETRY_TIMEOUT seconds: 

2005-12-05 20:27:28: (mod_fastcgi.c.2493) fcgi-server re-enabled: 192.168.5.85 3001
2005-12-05 20:27:29: (mod_fastcgi.c.2665) establishing connection failed: Connection refused
2005-12-05 20:27:29: (mod_fastcgi.c.2804) fcgi-server disabled: 192.168.5.85 3001

i propose to check the fcgi-server:

  1. in tcp level (establish tcp connection).
  2. fcgi protocol level.

and if those succeed, mark fcgi-server online, and send next request there.

i'm not sure, but i think it's possible to do fcgi service check without actually doing FCGI_BEGIN_REQUEST. because sending actual request to fcgi-server to test if it's alive is not very safe operation.

04/21/2007 10:02:15 PM changed by mike503

whatever the intelligent solution is here please make sure it's implemented into the mod_proxy_core replacement for fcgi in 1.5 :) thanks.

Add/Change #36 (fcgi remote backends intelligent availability check)




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