Varnish 2.0.5 - question on health status

[Jim Hayter]

Running varnish 2.0.5 on Ubuntu 9.10.

I have a question about how health checks are handled.  As shown in the varnishlog entries below, the server stopped responding to the health checks.  Once the count of successful checks dropped below 7 out of 10, it went sick. (Backend config for server also included below).

What I find confusing is that immediately after that the health checks started succeeding but the count of successful checks out of the last 10 remained at 6 until 7 successive health checks succeeded and the count went to 7.  It looks like being sick dropped the count to zero but didn't report that.  Is this the way it should work?


    0 Backend_health - server_abc Still healthy 4--X-S-RH 10 7 10 0.230660 0.097101 HTTP/1.1 200 OK
    0 Backend_health - server_abc Still healthy 4--X-S--- 9 7 10 0.000000 0.097101
    0 Backend_health - server_abc Still healthy 4--X-S--- 8 7 10 0.000000 0.097101
    0 Backend_health - server_abc Still healthy 4--X-S--- 7 7 10 0.000000 0.097101
    0 Backend_health - server_abc Went sick 4--X-S--- 6 7 10 0.000000 0.097101
    0 Backend_health - server_abc Still sick 4--X-S-RH 6 7 10 0.694192 0.246374 HTTP/1.1 200 OK
    0 Backend_health - server_abc Still sick 4--X-S-RH 6 7 10 0.025580 0.191176 HTTP/1.1 200 OK
    0 Backend_health - server_abc Still sick 4--X-S-RH 6 7 10 0.022060 0.148897 HTTP/1.1 200 OK
    0 Backend_health - server_abc Still sick 4--X-S-RH 6 7 10 0.018023 0.116178 HTTP/1.1 200 OK
    0 Backend_health - server_abc Still sick 4--X-S-RH 6 7 10 0.019373 0.091977 HTTP/1.1 200 OK
    0 Backend_health - server_abc Still sick 4--X-S-RH 6 7 10 0.073107 0.087259 HTTP/1.1 200 OK
    0 Backend_health - server_abc Back healthy 4--X-S-RH 7 7 10 0.172980 0.108689 HTTP/1.1 200 OK
    0 Backend_health - server_abc Still healthy 4--X-S-RH 8 7 10 0.076496 0.100641 HTTP/1.1 200 OK
    0 Backend_health - server_abc Still healthy 4--X-S-RH 9 7 10 0.026741 0.082166 HTTP/1.1 200 OK
    0 Backend_health - server_abc Still healthy 4--X-S-RH 10 7 10 0.020648 0.066786 HTTP/1.1 200 OK


Backend server stanza in vcl:

backend server_abc {
    .host = "server_abc";
    .port = "8080";
    .connect_timeout = 1s;
    .first_byte_timeout = 20s;
    .probe = {
        .request =
            "HEAD /favicon.ico HTTP/1.1"
            "Host: www.<domain>"
            "User-Agent: varnish health probe"
            "Connection: close" ;
        .timeout = 1s;
        .interval = 2s;
        .window = 10;
        .threshold = 7; }
}

Thanks,
Jim
--
Jim Hayter