[Varnish] #1658: Hash and Random director is deflected at the health-check failover

[Varnish]

#1658: Hash and Random director is deflected at the health-check failover
-------------------+--------------------
 Reporter:  xcir   |       Type:  defect
   Status:  new    |   Priority:  normal
Milestone:         |  Component:  vmod
  Version:  trunk  |   Severity:  normal
 Keywords:         |
-------------------+--------------------
 I have noticed that failover is deflected.

 If health-check failures, select to other backend.
 But, selected backend is near for seed is same.

 --vcl
 {{{
 vcl 4.0;

 import directors;

 backend b1 { .host = "127.0.0.1";.port = "88";}
 backend b2 { .host = "127.0.0.1";.port = "88";}
 backend b3 { .host = "127.0.0.1";.port = "88";}
 backend b4 { .host = "127.0.0.1";.port = "88";}

 sub vcl_init{
   new ws_rand  = directors.random();
   ws_rand.add_backend(b1, 1.0);
   ws_rand.add_backend(b2, 1.0);
   ws_rand.add_backend(b3, 1.0);
   ws_rand.add_backend(b4, 1.0);
 }
 sub vcl_recv{
   set req.backend_hint = ws_rand.backend();
   return(pass);
 }
 }}}
 --command
 {{{
 test:
 #ab -n 1200 -c1 http://localhost/

 get log:
 # varnishlog -graw -ibackend> z
 # cat z|sed -e 's/\s\+/\t/g'|cut -f 7|sort | uniq -c
 }}}

 --log
 {{{
 All backend is healthy:
     298 b1(127.0.0.1,,88)
     313 b2(127.0.0.1,,88)
     304 b3(127.0.0.1,,88)
     285 b4(127.0.0.1,,88)

 b1 is sick:
     605 b2(127.0.0.1,,88)<-It's heavy..
     307 b3(127.0.0.1,,88)
     288 b4(127.0.0.1,,88)

 b2 is sick:
     388 b1(127.0.0.1,,88)
     519 b3(127.0.0.1,,88)
     293 b4(127.0.0.1,,88)

 b3 is sick:
     325 b1(127.0.0.1,,88)
     488 b2(127.0.0.1,,88)
     387 b4(127.0.0.1,,88)

 b4 is sick:
     301 b1(127.0.0.1,,88)
     310 b2(127.0.0.1,,88)
     589 b3(127.0.0.1,,88)
 }}}

 I've created a patch to re-hash the seed at the failover.


 --log(patched)
 {{{
 All backend is healthy:
     294 b1(127.0.0.1,,88)
     303 b2(127.0.0.1,,88)
     318 b3(127.0.0.1,,88)
     285 b4(127.0.0.1,,88)

 b1 is sick:
     356 b2(127.0.0.1,,88)
     429 b3(127.0.0.1,,88)
     415 b4(127.0.0.1,,88)

 b2 is sick:
     439 b1(127.0.0.1,,88)
     366 b3(127.0.0.1,,88)
     395 b4(127.0.0.1,,88)

 b3 is sick:
     425 b1(127.0.0.1,,88)
     394 b2(127.0.0.1,,88)
     381 b4(127.0.0.1,,88)

 b4 is sick:
     394 b1(127.0.0.1,,88)
     405 b2(127.0.0.1,,88)
     401 b3(127.0.0.1,,88)
 }}}

-- 
Ticket URL: <https://www.varnish-cache.org/trac/ticket/1658>
Varnish <https://varnish-cache.org/>
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