Now, both the Liferay Portal server nodes are ready. As a next step, we need to configure the Apache Web Server to connect with both the Liferay Portal nodes and also distribute the load on both the Liferay Portal nodes. The Apache Web Server provides many options to connect with the Liferay Portal Tomcat server. But there are three options which are more popular. Let's understand these options and the scenarios in which they are best suitable.
This option allows us to configure the load balancer using the mod_jk module of the Apache Web server. Internally, the mod_jk module connects with the Liferay Portal Tomcat server using the AJP protocol. Using this option, the Apache Web Server distributes all requests on the AJP port of Liferay Portal Tomcat servers. Let's learn how to configure the software load balancer using this option.
- Download and copy the
mod_jkmodule in the<APACHE_HOME>/modulesdirectory. - Create a new file called
mod_jk.confin the<APACHE_HOME>/confdirectory, and add the following configuration into it:LoadModule jk_module modules/mod_jk.so JkWorkersFile /etc/httpd/conf/workers.properties JkShmFile /var/log/httpd/mod_jk.shm JkLogFile /var/log/httpd/mod_jk.log JkLogLevel info JkLogStampFormat "[%a %b %d %H:%M:%S %Y] " JkMount /* loadbalancer
- Now edit the
httpd.conffile located in the<APACHE_HOME>/confdirectory, and add the following line at the bottom:Includemod_jk.conf
- Add a new file called
worker.propertiesin the<APACHE_HOME>/confdirectory, and add the following lines into it:#Name of the load balancer workers worker.list=loadbalancer #Worker configuration for liferay-node-01 #AJP Connector port of node-01 on liferay-node-01 server worker.node-01.port=8009 worker.node-01.host=<IP of liferay-node-01 server> worker.node-01.type=ajp13 #Factor which decides the load sharing by this worker in the cluster worker.node-01.lbfactor=1 #Worker configuration for liferay-node-02 worker.node-02.port=8009 worker.node-02.host=<IP of liferay-node-02 server> worker.node-02.type=ajp13 worker.node-02.lbfactor=1 #load balancer configuration properties worker.loadbalancer.type=lb #list of worker nodes that are part of the cluster worker.loadbalancer.balance_workers=node-01,node-02 worker.loadbalancer.sticky_session=1 worker.loadbalancer.method=B
- Now edit the
server.xmlfile ofliferay-node-01located innode-01liferay-portal-6.1.1-ce-ga2 tomcat-7.0.27conf, and add thejvmRouteattribute to the<Engine>tag as given here:<Engine defaultHost="localhost" name="Catalina" jvmRoute="node-01">
- Similarly, add the
jvmRouteparameter inserver.xmlofliferay-node-02. Here the value ofjvmRoutewill benode-02. - We are ready to test our configuration. Restart both the Liferay Portal nodes and the Apache Web Server to test the configuration. We can access Liferay Portal directly by using the
http://<Apache Web Server IP>URL.
To connect the Apache Web Server with the Liferay Portal Tomcat server, we installed the mod_jk module in the Apache Web Server. We then configured the Apache Web Server to load the mod_jk module and provided the mod_jk configuration parameters. We defined the logfile and shared memory file locations and logfile formats for the mod_jk module. The most important configuration is to add worker nodes on which we want to distribute the load. We defined this by providing the worker configuration file. In the worker configuration file, we defined two Liferay Portal nodes. We then configured the load balancer and added Liferay Portal nodes to it. We configured the load balancer method to Busyness (B) which means, the load balancer will distribute the requests depending upon the load on Liferay Portal Tomcat servers. Other possible load balancer methods include By Requests (distributes the load based on the number of requests and load factor of the worker) and By Traffic (distributes load based on the traffic in bytes and load factor). Finally, we enabled session stickiness. Session stickiness is used to distribute all the requests for a specific session to a specific Liferay Portal Server node. Only in case of failure of the specific node, subsequent requests will be served by the other node. It is very important to use the sticky session feature to save resources. In order to make sure the sticky session functionality works fine, we configured jvmRoute in both the Tomcat nodes with unique values. The Apache Web Server appends jvmRoute in the session ID and based on the jvmRoute value, the Apache Web Server can ensure sending requests to the right Liferay Portal Tomcat node.
Another way to configure the software load balancer using Apache Web Server is through the mod_proxy_ajp and mod_proxy_balancer modules. This is a newer approach introduced in Apache Web Server 2.2. It uses the mod_proxy module and connects the Liferay Portal server using the AJP protocol. Let's understand how to configure the software load balancer using this option.
- Create a new file called
mod_proxy_ajp.confin the<APACHE_HOME>/confdirectory, and add the following content:LoadModuleproxy_modulemodules/mod_proxy.so LoadModule proxy_ajp_module modules/mod_proxy_ajp.so LoadModule proxy_balancer_module /modules/mod_proxy_balancer.so
- In the same file, add the following configuration settings:
<VirtualHost *:80> ServerName localhost.localdomain ErrorLog /var/log/apache2/ajp.error.log CustomLog /var/log/apache2/ajp.log combined <Proxy *> AddDefaultCharSet Off Order deny,allow Allow from all </Proxy> ProxyPass / balancer://ajpCluster/ stickysession=JSESSIONID ProxyPassReverse / balancer://ajpCluster/ stickysession=JSESSIONID <Proxy balancer://ajpCluster> BalancerMember ajp://<IP of liferay-node-01>:8009 route=node-01 BalancerMember ajp:// <IP of liferay-node-02>:8009 route=node-02 ProxySet lbmethod=byrequests </Proxy> </VirtualHost> - Now edit the
httpd.conffile located in the<APACHE_HOME>/confdirectory, and add the following lines at the bottom:Include mod_proxy_ajp.conf
- Now, edit the
server.xmlfile ofliferay-node-01located innode-01liferay-portal-6.1.1-ce-ga2 tomcat-7.0.27conf, and add thejvmRouteattribute to the<Engine>tag as shown here:<Engine defaultHost="localhost" name="Catalina" jvmRoute="node-01">
- Similarly, add the
jvmRouteparameter inserver.xmlofliferay-node-02. Here the value ofjvmRoutewill benode-02. - Now restart both the Liferay Portal Servers and the Apache Web server, and test the configuration using the
http://<Apache Web Server IP>URL.
This approach requires the mod_proxy, mod_proxy_ajp and mod_proxy_balancer modules. These modules, by default, ship with the Apache Web Server binary. We enabled them by using the LoadModule command. We then configured the virtual host for our local instance. In the virtual host configuration, we provided the locations of the logfiles. We added the load balancer using the <Proxy balancer> tag. Again in the load balancer configuration, we provided the hostname and port of both the Liferay Portal Servers. We also provided the jvmRoute value using the route parameter. This parameter must match with jvmRoute configured in steps 4 and 5. We also configured the load balancing method to By Requests (byrequests). This load balancing method distributes the load on both the Liferay Portal servers in a round robin manner. We also configured the virtual host to route all the requests to the load balancer using the mod_proxy configuration. We configured to use session stickiness through the mod_proxy configuration.
This method is very similar to mod_proxy_ajp. The only difference here is the load balancer configuration. Here the Apache Web Server and the Liferay Portal Tomcat server will connect using the HTTP or HTTPS protocol. So let's configure the load balancer using this option.
- Similar to previous options, we need to load the necessary modules. Create a new file called
mod_proxy_http.confin the<APACHE_HOME>/confdirectory and add the following content:LoadModuleproxy_modulemodules/mod_proxy.so LoadModule proxy_http_module modules/mod_proxy_http.so LoadModule proxy_balancer_module /modules/mod_proxy_balancer.so
- In the same file, add the following configuration settings:
<VirtualHost *:80> ServerName localhost.localdomain ErrorLog /var/log/apache2/http.error.log CustomLog /var/log/apache2/http.log combined <Proxy *> AddDefaultCharSet Off Order deny,allow Allow from all </Proxy> ProxyPass / balancer://httpCluster/ stickysession=JSESSIONID ProxyPassReverse / balancer://httpCluster/ stickysession=JSESSIONID <Proxy balancer://httpCluster> BalancerMember http:// <IP of liferay-node-01>:8080 route=node-01 BalancerMember http:// <IP of liferay-node-02>:8080 route=node-02 ProxySet lbmethod=byrequests </Proxy> </VirtualHost> - Now edit the
httpd.conffile located in the<APACHE_HOME>/confdirectory and add the following line at the bottom:Include mod_proxy_http.conf
- Now edit the
server.xmlfile ofliferay-node-01located innode-01liferay-portal-6.1.1-ce-ga2 tomcat-7.0.27conf, and add thejvmRouteattribute to the<Engine>tag as follows:<Engine defaultHost="localhost" name="Catalina" jvmRoute="node-01">
- Similarly, add the
jvmRouteparameter inserver.xmlofliferay-node-02. Here the value ofjvmRoutewill benode-02. - Now restart both the Liferay Portal Servers and the Apache Web server and test the configuration using the
http://<IP of Apache Web Server>URL.
These steps are very similar to the previous option. The only difference is that we are using the HTTP protocol. This connector allows us to establish an encrypted connection between the web server and the Liferay Portal application server using the HTTPS protocol.
We have learned three different methods of configuring the software load balancer using the Apache Web Server. Now let's learn some of the best practices associated with these options:
- The software load balancer configuration using
mod_jkis most recommended becausemod_jkis a reliable and error free module compared to other options. From the performance point of view it gives the best performance. Themod_proxy_ajpmodule is similar tomod_jkbut it is relatively new. If there is a need to use a secured connection between the Apache Web Server and Liferay Portal Tomcat server, we can consider using themod_proxy_httpmodule. It provides easy configuration to implement this scenario. - We learned that the Liferay Portal Tomcat server and the Apache Web Server either connect using the AJP connector or the HTTP connector. None of the connectors use both the connectors at the same time. The Liferay Portal Tomcat server, by default, enables both the connectors. It is a best practice to disable the connector which we are not using. This can save resources on the Liferay Portal application server. We can disable any of the connectors by commenting the respective
<Connector>tag from theserver.xmlfile of the Liferay Portal Tomcat server. - It is advisable to select the load balancer method carefully. Depending upon the nature of the application, the right load balancer method should be chosen. If we are using the
mod_jkconnector, it is recommended to use the Busyness load balancer method. This will help in distributing requests on Liferay Portal servers with respect to their current load.