I have set up an Apache Tomcat Cluster with an Apache HTTP server and load balancing on CentOS 6.6 the following way:
+ 1 VM running HTTP server & 1 Tomcat instance (used for deployment, not answering requests)
+ 1 VM running 2 Tomcat instances on different ports
Important things first:
+ watchEnabled: on master = "true", on slaves = "false"
+ HTTP connector only for master node, not defined on slaves
+ port for AJP connector different on every instance
+ tcpListenerPort for NioReceiver different on every instance
+ jvmRoute value equals respective hostname on all instances
+ path to watchDir / tempDir different, deployDir = webapps on every instance
+ port for shutdown different on every instance
+ firewalld/iptables turned off on all nodes (testing environment)
+ YES, I have read lots of things about this topic (official documentation, tutorials, etc...) already.
server.xml (only the important part)
<Server port="8004" shutdown="SHUTDOWN">
<Service name="Catalina">
<!-- HTTP connector on port 8081 -->
<Connector
connectionTimeout="20000"
port="8081" protocol="HTTP/1.1"
redirectPort="8443"/>
<!-- Define an AJP 1.3 Connector on port 8012 -->
<Connector
port="8012"
protocol="AJP/1.3"
redirectPort="8443"/>
<!-- Engine definition for clustering -->
<Engine
defaultHost="localhost"
jvmRoute="acd10-master"
name="Catalina">
<Realm className="org.apache.catalina.realm.MemoryRealm"/>
<Host
appBase="webapps"
autoDeploy="true"
name="192.168.2.139"
undeployOldVersions="true"
unpackWARs="true">
<Cluster
channelSendOptions="6"
className="org.apache.catalina.ha.tcp.SimpleTcpCluster"
useDirtyFlag="true">
<ClusterListener className="org.apache.catalina.ha.session.ClusterSessionListener"/>
<Valve className="org.apache.catalina.ha.tcp.ReplicationValve" filter=""/>
<Valve className="org.apache.catalina.ha.session.JvmRouteBinderValve"/>
<Channel className="org.apache.catalina.tribes.group.GroupChannel">
<Membership
address="228.0.0.4"
className="org.apache.catalina.tribes.membership.McastService"
dropTime="3000"
frequency="500"
port="45564"/>
<Receiver
address="auto"
className="org.apache.catalina.tribes.transport.nio.NioReceiver"
maxThreads="6"
port="4005"
timeout="100"/>
<Sender className="org.apache.catalina.tribes.transport.ReplicationTransmitter">
<Transport
className="org.apache.catalina.tribes.transport.nio.PooledParallelSender"/>
</Sender>
<Interceptor
className="org.apache.catalina.tribes.group.interceptors.TcpFailureDetector"/>
<Interceptor
className="org.apache.catalina.tribes.group.interceptors.MessageDispatch15Interceptor"/>
<Interceptor
className="org.apache.catalina.tribes.group.interceptors.ThroughputInterceptor"/>
</Channel>
<Deployer
className="org.apache.catalina.ha.deploy.FarmWarDeployer"
deployDir="/usr/local/tomcat7/webapps/"
tempDir="/usr/local/tomcat7/war-temp/"
watchDir="/usr/local/tomcat7/war-watch/"
watchEnabled="true"/>
</Cluster>
</Host>
</Engine>
</Service>
</Server>
mod_proxy.conf
<VirtualHost *:80>
DocumentRoot /var/www/html
ProxyRequests Off
ProxyPreserveHost On
<Proxy *>
Order deny,allow
Allow from all
</Proxy>
<Proxy balancer://testcluster>
BalancerMember ajp://192.168.2.166:8010/ route=acd11-node01
BalancerMember ajp://192.168.2.166:8011/ route=acd11-node02
ProxySet lbmethod=byrequests
</Proxy>
# Exclude balancer-manager app to make it available on master
ProxyPass /balancer-manager !
ProxyPass / balancer://testcluster/ stickysession=JSESSIONID|jsessionid
ProxyPassReverse / balancer://testcluster/ stickysession=JSESSIONID|jsessionid
<Location /balancer-manager>
SetHandler balancer-manager
</Location>
</VirtualHost>
EDIT:
Apache error log (what it gives me after startup):
[Tue Jan 06 08:29:49.235859 2015] [mpm_prefork:notice] [pid 9655] AH00170: caught SIGWINCH, shutting down gracefully
[Tue Jan 06 08:29:50.306520 2015] [core:notice] [pid 9727] SELinux policy enabled; httpd running as context system_u:system_r:httpd_t:s0
[Tue Jan 06 08:29:50.307867 2015] [suexec:notice] [pid 9727] AH01232: suEXEC mechanism enabled (wrapper: /usr/sbin/suexec)
[Tue Jan 06 08:29:50.319218 2015] [so:warn] [pid 9727] AH01574: module proxy_module is already loaded, skipping
[Tue Jan 06 08:29:50.319797 2015] [so:warn] [pid 9727] AH01574: module proxy_ajp_module is already loaded, skipping
[Tue Jan 06 08:29:50.319827 2015] [so:warn] [pid 9727] AH01574: module proxy_balancer_module is already loaded, skipping
[Tue Jan 06 08:29:50.320610 2015] [so:warn] [pid 9727] AH01574: module proxy_http_module is already loaded, skipping
AH00558: httpd: Could not reliably determine the server's fully qualified domain name, using fe80::50a0:e2ff:fe74:5294. Set the 'ServerName' directive globally to suppress this message
[Tue Jan 06 08:29:50.328101 2015] [auth_digest:notice] [pid 9727] AH01757: generating secret for digest authentication ...
[Tue Jan 06 08:29:50.329387 2015] [lbmethod_heartbeat:notice] [pid 9727] AH02282: No slotmem from mod_heartmonitor
[Tue Jan 06 08:29:50.333216 2015] [mpm_prefork:notice] [pid 9727] AH00163: Apache/2.4.6 (CentOS) configured -- resuming normal operations
[Tue Jan 06 08:29:50.333263 2015] [core:notice] [pid 9727] AH00094: Command line: '/usr/sbin/httpd -D FOREGROUND'
What I try to achieve:
We have many enterprise web applications which we wanna load balance throughout a Tomcat farm.
What does work:
+ Tomcat clustering
+ Replication
+ FarmWarDeployer
What doesn't work:
Whenever I try to call an application that's been deployed throughout the cluster, it gives me 404 not found. Same for Tomcat root applications such as /manager/html or /host-manager. Only application that is working is /balancer-manager, obviously.
The httpd server is supposed to serve as a load balancer and proxy to the tomcats. It will have to deliver some static content but first and foremost, I need to get this thing up and running to load balance the JavaEE applications (servlets). AJP to the cluster nodes is a must have for me, since http access must not be allow (+ for some other reasons that are worth a totally different discussion).
Since everybody seems to set up the mod_proxy configuration in a different manner, I am looking for a straight forward solution that gives me something I can build on. If you need more information or more configuration details, let me know and I will provide you with those. I already have a second cluster configured using mod_jk and everything is working as intended, but the Stakeholders require this mod_proxy(_ajp) thing and it just grinds my gears.
Your help is much appreciated!
Best regards!
