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The following modules need to be activated in order to do load balancing on several cluster nodes :
mod_proxy_balancer
mod_slotmem_shm (mandatory for mod_proxy_balancer)
mod_lbmethod_byrequests if you choose the by request balancing algorithm (can be also mod_lbmethod_bytraffic or mod_lbmethod_bybusyness)
Part of an apache configuration to enabled load balancing :
# Add a http header to explicitly identify the node and be sticky
Header add Set-Cookie "ROUTEID=.%{BALANCER_WORKER_ROUTE}e; path=/" env=BALANCER_ROUTE_CHANGED
# Declare the http server pool
<Proxy "balancer://plf">
BalancerMember "http://node1:8080" route=node1 acquire=2000 retry=5 keepalive=on ping=30 connectiontimeout=2
BalancerMember "http://node2:8080" route=node2 acquire=2000 retry=5 keepalive=on ping=30 connectiontimeout=2
ProxySet stickysession=ROUTEID
</Proxy>
# Declare the pool dedicated to the websocket tunnels
<Proxy "balancer://plf_ws">
BalancerMember "ws://node1:8080" route=node1 acquire=2000 retry=0 keepalive=on ping=30 connectiontimeout=2 disablereuse=on flushpackets=on
BalancerMember "ws://node2:8080" route=node2 acquire=2000 retry=0 keepalive=on ping=30 connectiontimeout=2 disablereuse=on flushpackets=on
ProxySet stickysession=ROUTEID
</Proxy>
# Common options
ProxyRequests Off
ProxyPreserveHost On
# Declare the redirection for websocket urls, must be declared before the general ProxyPass definition
ProxyPass /cometd "balancer://plf_ws/cometd"
# Declare the redirection for the http requests
ProxyPass / "balancer://plf/"
ProxyPassReverse / "balancer://plf/"
This configuration must be adapted to you specific needs before you go to production.
All the configuration detail can be found on the Apache configuration page
See also