Problem Upgrade to Varnish 4.1 - Multiple Backends Not Working

Drew, AJ Drew.AJ at
Fri Sep 23 15:20:46 CEST 2016

Sorry for not being for specific.

The initial backend being set is the one that is always used no matter what the URL.

So, when I come in with a URL of /syscheck/blah.htm, I would expect the alternative backend to be used.  It does not get select, and instead the original one is the one used, and therefore I end up with either a HTTP 404 or a HTTP 503, depending on the mood of Drupal the destination of the initial backend.


A J Drew

Here is some output from varnishlog of a call:

         2 Begin          c req 1 rxreq
         2 Timestamp      c Start: 1474629889.600227 0.000000 0.000000
         2 Timestamp      c Req: 1474629889.600227 0.000000 0.000000
         2 ReqStart       c 34608
         2 ReqMethod      c GET
         2 ReqURL         c /syscheck/wwwul2370.htm
         2 ReqProtocol    c HTTP/1.1
         2 ReqHeader      c Host:
         2 ReqHeader      c Accept: text/html, application/xhtml+xml, */*
         2 ReqHeader      c Accept-Language: en-US
         2 ReqHeader      c User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; rv:11.0) like Gecko
         2 ReqHeader      c Accept-Encoding: gzip, deflate
         2 ReqHeader      c Cookie: ObSSOCookie=loggedout; TLTSID=A5D86DBA4DA97DFA943BD59DA9EFF5B8; dtCookie=3A7E953F591088FA2F6DB23E157B3A54|Q1NTX19FQV9fYXV0aG9yaXphdGlvbi1oYW5kbGVyLWVhcnwxfENTU19fRUFfX2FjY291bnQtYWdncmVnYXRpb24tZWFyfDE; dtLatC=36971; dtPC=-; RANDOM_ID=6529725af06
         2 ReqHeader      c Via: 1.1
         2 ReqHeader      c X-Forwarded-For:
         2 ReqHeader      c X-Forwarded-Host:
         2 ReqHeader      c X-Forwarded-Server:
         2 ReqHeader      c Connection: Keep-Alive
         2 ReqUnset       c X-Forwarded-For:
         2 ReqHeader      c X-Forwarded-For:,
         2 VCL_call       c RECV
         2 VCL_return     c pass
         2 VCL_call       c HASH
         2 VCL_return     c lookup
         2 VCL_call       c PASS
         2 VCL_return     c fetch
         2 Link           c bereq 3 pass
         2 Timestamp      c Fetch: 1474629891.152683 1.552456 1.552456
         2 RespProtocol   c HTTP/1.1
         2 RespStatus     c 404
         2 RespReason     c Not Found
         2 RespHeader     c Date: Fri, 23 Sep 2016 11:24:49 GMT
         2 RespHeader     c Server: Apache
         2 RespHeader     c X-Drupal-Cache: MISS
         2 RespHeader     c Expires: Sun, 19 Nov 1978 05:00:00 GMT
         2 RespHeader     c Cache-Control: public, max-age=3600
         2 RespHeader     c Content-Language: en
         2 RespHeader     c X-Generator: Drupal 7 (
         2 RespHeader     c Etag: "1474629889-0"
         2 RespHeader     c Last-Modified: Fri, 23 Sep 2016 11:24:49 GMT
         2 RespHeader     c Vary: Cookie,Accept-Encoding
         2 RespHeader     c Strict-Transport-Security: max-age=31536000; includeSubDomains; preload
         2 RespHeader     c X-XSS-Protection: 1;
         2 RespHeader     c Content-Type: text/html; charset=utf-8
         2 RespHeader     c X-Varnish: 2
         2 RespHeader     c Age: 0
         2 RespHeader     c Via: 1.1 varnish-v4
         2 VCL_call       c DELIVER
         2 RespHeader     c X-Cache: MISS
         2 RespUnset      c Via: 1.1 varnish-v4
         2 RespUnset      c X-Generator: Drupal 7 (
         2 RespUnset      c Server: Apache
         2 VCL_return     c deliver
         2 Timestamp      c Process: 1474629891.152737 1.552510 0.000054
         2 RespHeader     c Content-Length: 7685
         2 Debug          c "RES_MODE 2"
         2 RespHeader     c Connection: keep-alive
         2 Timestamp      c Resp: 1474629891.152783 1.552556 0.000046
         2 ReqAcct        c 791 0 791 500 7685 8185
         2 End            c

From: Guillaume Quintard [mailto:guillaume at]
Sent: Friday, September 23, 2016 8:12 AM
To: Drew, AJ
Cc: varnish-misc at
Subject: Re: Problem Upgrade to Varnish 4.1 - Multiple Backends Not Working

What does "stop working" mean? Does the vcl fail to compile? do you receive 503s? does it open a portal to an ancient dimension filled with unspoken nightmares? Help us help you.

Guillaume Quintard

On Fri, Sep 23, 2016 at 1:52 PM, Drew, AJ <Drew.AJ at<mailto:Drew.AJ at>> wrote:

We are trying to upgrade to Varnish 4.1 from Varnish 3.0.5.

Most things are working fine, but a big problem we are running into is that we have multiple backends.  We switch backends based on URLs.  This was working fine in Varnish 3, but when we switched over to Varnish 4, it stopped working.

I have tried many variations of the URLs, and even simplified the directors so that they only contain one backend (in my tests) so that I could switch from trying the backend directly to trying the director.

Using either of the options does not seem to matter.

Has anyone else run into this problem?

Here are the sections of my VCL that contain the backends / director definitions and the if statements to switch.  I have also left in the different options (lines) I have used to come up with different combinations for testing.

probe B_probe {
        .request =
        "GET  /zzzzzz/status.php HTTP/1.1"
        "Connection: close";
        .timeout   = 0.3 s;
        .window    = 8;
        .threshold = 7;

backend B_backend1 {
        .host = "";
        .port = "8080";
        .probe = B_probe;

backend syscheck {
#        .host = "localhost";
        .host = "";
        .port = "8081";

backend searchBackend {
        .host = "<>";
        .port = "80";

backend providerBackend {
        .host = "";
        .port = "80";

sub vcl_init {
        new examplehosts = directors.round_robin();

        new examplesyscheck = directors.round_robin();

sub vcl_recv {

#       set req.backend_hint = examplehosts.backend();
        set req.backend_hint = B_backend1;

        if (req.url ~ "^/syscheck/.*$") {
#       if (req.url ~ "^/syscheck/*") {
#       if (req.url ~ "^/syscheck/") {
                set req.backend_hint = syscheck;
#               set req.backend_hint = examplesyscheck.backend();

        # Add simple health check for upstream load balancers
        if (req.url ~ "^/health-check") {
                return( synth(200, "UP"));


A J Drew

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