[MEDIUM] add support for "maxqueue" to limit server queue overload
This patch adds the "maxqueue" parameter to the server. This allows new
sessions to be immediately rebalanced when the server's queue is filled.
It's useful when session stickiness is just a performance boost (even a
huge one) but not a requirement.
This should only be used if session affinity isn't a hard functional
requirement but provides performance boost by keeping server-local
caches hot and compact).
Absence of 'maxqueue' option means unlimited queue. When queue gets filled
up to 'maxqueue' client session is moved from server-local queue to a global
one.
diff --git a/doc/haproxy-en.txt b/doc/haproxy-en.txt
index 09d311e..3e8ce10 100644
--- a/doc/haproxy-en.txt
+++ b/doc/haproxy-en.txt
@@ -1364,6 +1364,21 @@
will receive only 10 simultaneous sessions when the proxy will be under 1000
sessions.
+It is possible to limit server queue length in order to rebalance excess
+sessions between less busy application servers IF session affinity isn't
+hard functional requirement (for example it just gives huge performance boost
+by keeping server-local caches hot and compact). 'maxqueue' option sets a
+queue limit on a server, as in example below:
+
+... (just the same as in example above)
+ server pentium3-800 192.168.1.1:80 cookie s1 weight 8 minconn 10 maxconn 100 check maxqueue 50
+ server opteron-2.0G 192.168.1.2:80 cookie s2 weight 20 minconn 30 maxconn 300 check maxqueue 200
+ server opteron-2.4G 192.168.1.3:80 cookie s3 weight 24 minconn 30 maxconn 300 check
+
+Absence of 'maxqueue' option means unlimited queue. When queue gets filled
+up to 'maxqueue' client session is moved from server-local queue to a global
+one.
+
Notes :
-------
- The requests will not stay indefinitely in the queue, they follow the