Lighttpd error sockets disabled, out-of-fds - fastcgi

Question

I have used lighttpd for a long, since its very fast for busy webapplications ins fast-cgi(PHP)
2 or 3 months ago sometimes I got this erro:
2015-07-06 17:58:55: (server.c.1398) [note] sockets enabled again
2015-07-06 17:58:55: (server.c.1446) [note] sockets disabled, out-of-fds
2015-07-06 17:58:59: (server.c.1398) [note] sockets enabled again
2015-07-06 17:58:59: (server.c.1446) [note] sockets disabled, out-of-fds
2015-07-06 17:59:05: (server.c.1398) [note] sockets enabled again
2015-07-06 17:59:05: (server.c.1446) [note] sockets disabled, out-of-fds
2015-07-06 17:59:10: (server.c.1398) [note] sockets enabled again
2015-07-06 17:59:10: (server.c.1446) [note] sockets disabled, out-of-fds
2015-07-06 17:59:14: (server.c.1398) [note] sockets enabled again
2015-07-06 17:59:14: (server.c.1446) [note] sockets disabled, out-of-fds
2015-07-06 17:59:18: (server.c.1398) [note] sockets enabled again
2015-07-06 17:59:18: (server.c.1446) [note] sockets disabled, out-of-fds
2015-07-06 17:59:22: (server.c.1398) [note] sockets enabled again
2015-07-06 17:59:22: (server.c.1446) [note] sockets disabled, out-of-fds
2015-07-06 17:59:26: (server.c.1398) [note] sockets enabled again
2015-07-06 17:59:26: (server.c.1446) [note] sockets disabled, out-of-fds
I was using version 1.4.29 and now after upgrade to 1.4.35 the problem persists. Since then I've been looking very different solutions and found nothing that could help me.
Some relevant config info:
h2. lighttpd.conf
server.username = "lighttpd"
server.groupname = "lighttpd"
server.event-handler = "linux-sysepoll"
server.max-fds = 4096 #same as ulimit -n
server.max-connections = 2048
server.stat-cache-engine = "simple"
server.max-keep-alive-idle = 5
server.max-keep-alive-requests = 4
server.max-read-idle = 30
server.max-write-idle = 360
h2. fast-cgi.conf
server.modules += ( "mod_fastcgi" )
fastcgi.server = ( ".php" =>
( "php-local" =>
(
"socket" => "/tmp/php-fastcgi-1.socket",
# "socket" => "/tmp/php-fastcgi-1.socket"+var.PID,
"bin-path" => "/usr/bin/php-cgi",
"max-procs" => 30,
"broken-scriptfilename" => "enable",
)
),
( "php-tcp" =>
(
"host" => "127.0.0.1",
"port" => 9999,
"check-local" => "disable",
"broken-scriptfilename" => "enable",
)
),
( "php-tcp2" =>
(
"host" => "127.0.0.1",
"port" => 9998,
"check-local" => "disable",
"broken-scriptfilename" => "enable",
)
),
( "php-num-procs" =>
(
"socket" => "/tmp/php-fastcgi-2.socket",
"bin-path" => "/usr/bin/php-cgi",
"max-procs" => 30,
"bin-environment" => (
"PHP_FCGI_CHILDREN" => "30",
"PHP_FCGI_MAX_REQUESTS" => "2048",
),
"broken-scriptfilename" => "enable",
)
),
)
This server is dedicated to that application.
Is running at more than four years with at least 2 lighttpd php applications with large volumes of access, the record was in 2013 with 14,000 unique visits and 85,000 page views, then this record had no problems with the limit.
Today keep the average 8,000 visitors and 44,000 page views per day.
:
What's wrong?

Answer 1

lighttpd 1.4 keeps an internal count of (some of the) file descriptors it has opened. lighttpd 1.4 disables the server sockets when its internal count (cur_fds + want_fds -- line 1408 of src/server.c) reaches 90% of server.max-fds from lighttpd.conf
It is possible (unsubstantiated) that the internal count does not match the actual number of file descriptors in use.
If this happens again, would you check how many fds are actually used by the lighttpd server process? If the lighttpd server process has pid 1234, then check the number of open fds of a process on Linux with
ls -1 /proc/1234/fd/ | wc -l
If the result is much less than 90% of server.max-fds (which you have set to 4096), then that would suggest a bug in lighttpd internal fd count. You can go to http://redmine.lighttpd.net/projects/lighttpd/issues and Register for an account. Then, you'll be able to submit a bug report.
Again, if this is the problem, you might also look at your application to see how frequently it is encountering fatal errors, dying, and being restarted.