backend polling mistery

[Jonas Kraw]

Dear All,

we have a strange random backend polling error.

There is a varnish box (2.1.4 running on debian lenny) for debugging and
testing which polls our two production backends:

a) STATICnode - nginx
b) APACHEnode - apache 2.2.9 with

Keepalive ON
Timeout 30
KeepAliveTimeout 12
MaxKeepAliveRequests 0
Prefork-MaxRequestsPerChild 20000

VCL:

backend APACHEnode {
    .host = "10.0.80.15";        .port = "8082";
    .probe = { .url = "/robots.txt"; .timeout = 10ms; .interval = 1s;
.window = 10; .threshold = 9; }
}
backend STATICnode {
    .host = "10.0.80.11";
    .port = "8080";
    .probe = { .url = "/robots.txt"; .timeout = 300ms; .interval = 2s;
.window = 10; .threshold = 8; }
}


The test case is for simulating our production varnish server, which acts
exactly the same way...

Here is the varnishlog:

   0 Backend_health - APACHEnode Still healthy 4--X-RH 9 9 10
0.000914 0.000993 HTTP/1.1 200 OK
   0 Backend_health - STATICnode Still healthy 4--X-RH 10 8 10
0.000354 0.000371 HTTP/1.1 200 OK
   0 Backend_health - APACHEnode Still healthy 4--X-RH 9 9 10
0.000686 0.000917 HTTP/1.1 200 OK
   0 Backend_health - APACHEnode Still healthy 4--X-RH 9 9 10
0.000639 0.000847 HTTP/1.1 200 OK
   0 Backend_health - STATICnode Still healthy 4--X-RH 10 8 10
0.000400 0.000379 HTTP/1.1 200 OK
   0 CLI          - Rd ping
   0 CLI          - Wr 200 19 PONG 1304944200 1.0
   0 Backend_health - APACHEnode Still healthy 4--X-RH 9 9 10
0.000685 0.000807 HTTP/1.1 200 OK
   0 Backend_health - APACHEnode Still healthy 4--X-RH 9 9 10
0.000696 0.000779 HTTP/1.1 200 OK
   0 Backend_health - STATICnode Still healthy 4--X-RH 10 8 10
0.000366 0.000376 HTTP/1.1 200 OK
   0 Backend_health - APACHEnode Went sick 4--X--- 8 9 10 0.000000
0.000779 HTTP/1.1 200 OK
Date: Mon, 09 May 2011 12:30:02 GMT
Server: Apache/2.2.9
Last-Modified: Fri, 08 Apr 2011 09:52:29 GMT
ETag:
   0 CLI          - Rd ping
   0 CLI          - Wr 200 19 PONG 1304944203 1.0
   0 Backend_health - APACHEnode Still sick 4--X-RH 8 9 10 0.002321
0.001165 HTTP/1.1 200 OK
   0 Backend_health - STATICnode Still healthy 4--X-RH 10 8 10
0.000367 0.000373 HTTP/1.1 200 OK
   0 Backend_health - APACHEnode Back healthy 4--X-RH 9 9 10 0.001611
0.001276 HTTP/1.1 200 OK
   0 Backend_health - APACHEnode Still healthy 4--X-RH 9 9 10
0.000676 0.001126 HTTP/1.1 200 OK
   0 Backend_health - STATICnode Still healthy 4--X-RH 10 8 10
0.000391 0.000378 HTTP/1.1 200 OK
   0 CLI          - Rd ping
   0 CLI          - Wr 200 19 PONG 1304944206 1.0
   0 Backend_health - APACHEnode Still healthy 4--X-RH 9 9 10
0.006641 0.002505 HTTP/1.1 200 OK
   0 Backend_health - APACHEnode Still healthy 4--X-RH 9 9 10
0.002885 0.002600 HTTP/1.1 200 OK
   0 Backend_health - STATICnode Still healthy 4--X-RH 10 8 10
0.000436 0.000392 HTTP/1.1 200 OK
   0 Backend_health - APACHEnode Still healthy 4--X-RH 9 9 10
0.000750 0.002137 HTTP/1.1 200 OK
   0 CLI          - Rd ping
   0 CLI          - Wr 200 19 PONG 1304944209 1.0
   0 Backend_health - APACHEnode Still healthy 4--X-RH 9 9 10
0.000787 0.001800 HTTP/1.1 200 OK
   0 Backend_health - STATICnode Still healthy 4--X-RH 10 8 10
0.000384 0.000390 HTTP/1.1 200 OK
   0 Backend_health - APACHEnode Still healthy 4--X-RH 9 9 10
0.000720 0.001530 HTTP/1.1 200 OK
   0 Backend_health - APACHEnode Still healthy 4--X-RH 9 9 10
0.000825 0.001354 HTTP/1.1 200 OK
^C

# varnishstat -1

client_conn                 0         0.00 Client connections accepted
client_drop                 0         0.00 Connection dropped, no sess/wrk
client_req                  0         0.00 Client requests received
cache_hit                   0         0.00 Cache hits
cache_hitpass               0         0.00 Cache hits for pass
cache_miss                  0         0.00 Cache misses
backend_conn                0         0.00 Backend conn. success
backend_unhealthy            0         0.00 Backend conn. not attempted
backend_busy                0         0.00 Backend conn. too many
backend_fail                0         0.00 Backend conn. failures
backend_reuse               0         0.00 Backend conn. reuses
backend_toolate             0         0.00 Backend conn. was closed
backend_recycle             0         0.00 Backend conn. recycles
backend_unused              0         0.00 Backend conn. unused


Can anyone give us a hint for tracking down this error?
Much Obliged

Jonas
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://www.varnish-cache.org/lists/pipermail/varnish-misc/attachments/20110509/d5a1d75b/attachment-0003.html>