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Once the Apache HTTP Server
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Using Apache HTTP server as a front-end to load-balance a cluster of Servoy Application Servers is optional. You should be able to do this in other ways, including custom balancing inside a Tomcat instance application or using other HTTP servers such as IIS that support (or have modules for) AJP1.3. Read through the section even if you do not plan to use Apache HTTP Server as it also shows configuration changes needed for Servoy Application Servers to run in a similar setup.
Smart clients will connect directly to the individual Servoy Application Servers in the cluster. The load-balancing is done by serving the JNLP file from different servers when the Apache HTTP front-end is accessed. Add to each of the Servoy Application Server's "servoy.properties" files the following line (needed for Smart Client load balancing):
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servoy.jnlpCodebaseOverride=http://thisServersHostnameAsSeenByClients:port
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What you should also take into consideration when setting up a load-balanced cluster, is allowing smart-clients to connect directly to individual servers in the cluster. This means that all Servoy Application Servers should be accessible from the client side - and you might want to isolate the cluster so that connections to ports used by Terracotta (see tc-config.xml) are only allowed from within the cluster, even if connections from client machines on Servoy ports should be allowed to all Servoy Application Servers.
3.1 Configure Apache HTTP Server
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is installed, it can be configured to operate as Load Balancer.
- Apply any standard configuration that you want/need (Listen, ServerName, ServerAdmin, ...) if any is needed to make HTTP server operational.
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- Copy 'mod_jk-1.2.28-httpd-2.2.3.so
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- ' to
{ApacheHTTPServerDir}/modules
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_
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- and
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- rename
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- it
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- to
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- 'mod_jk.so
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- '.
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- The name
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- might
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- depending
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- , see
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Add the lines below into
{ApacheHTTPServerDir}/conf/httpd.conf
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after
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all
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other
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LoadModule
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lines:
Code Block LoadModule jk_module modules/mod_jk.so # JK/Worker configuration # Where to find workers.properties JkWorkersFile conf/workers.properties # Where to put jk logs JkLogFile logs/mod_jk.log # Set the jk log level [debug/error/info] JkLogLevel info JkMount /* loadbalancer # In case you want to be able to monitor JK status # <Location /jkmanager/> # JkMount jkstatus # Order deny,allow # Deny from all # Allow from 127.0.0.1 # </Location>
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For more info on available options, see http://tomcat.apache.org/connectors-doc/webserver_howto/apache.html
- Copy worker.properties file from
{servoyInstall}/application_server/terracottadirectory to{ApacheHTTPServerDir}/conf. The default worker.properties file contains the configuration to load balance two Servoy application Servers, running on 2 different machines, both using port 8009. - Open the copied worker.properties and change the 'worker.servoyX.host' entries to the correct hostnames of the Servoy Application Servers. It is recommended to use port 8009 as well for all workers (default). If more than two Servoy Application Servers need to be load-balanced, add worker.servoyX sections and update worker.list and worker.loadbalancer.balance_workers
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- lines.
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- For
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- information
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- how
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- to
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- tune
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- workers,
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You have a possibility to monitor and control worker activity by uncommenting the "jkstatus" related comments in *worker.properties* and *httpd.conf* and accessing "_\[randd:yourServerUrl\]/jkmanager/_". This page will also allow you to activate/disable workers. You should add a worker for each Servoy Application Server that you will possibly start in your cluster, even if you do not plan to have them started all at once. There is no problem if only a part of those Servoy Application Servers are started. Load-balancing will work on servers defined in the *worker.properties* file that are also available. If you do define workers for Servoy Application Servers that are not started, disable them from the jkmanager page in order to avoid delays caused by load-balancer trying to check the availability of these workers. |
3.2 Configure each Servoy Tomcat Server in the cluster to work with the AJP 1.3 connector
This will describe how to set up the two Tomcat Servers in your Servoy installations as used by original worker.properties file above. You can adapt it when using more Servoy installations.
- Assume Servoy is installed twice, once on "servoyServer1Host" and once on "servoyServer2Host".
Wiki Markup In \[randd:servoy_install_folder\]/application_server/server/conf/server.xml:- Change line "<Engine name="Catalina" defaultHost="localhost">" into "<Engine jvmRoute="servoy1" name="Catalina" defaultHost="localhost">"; for second server use "servoy2".
- Add the following connector before the already declared one in both installations:
Code Block <Connector port="8009" enableLookups="false" maxThreads="500" connectionTimeout="60000" redirectPort="8443" useBodyEncodingForURI="true" protocol="AJP/1.3"/>
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It's possibility to monitor and control worker activity by uncommenting the 'jkstatus' related comments in worker.properties and httpd.conf and accessing {loadBalancerUrl}/jkmanager/. This page will also allow to activate/disable workers. A worker should be added for each Servoy Application Server that will possibly be started in the cluster, even when not planning to have them started all at once. There is no problem if only a part of those Servoy Application Servers are started. Load-balancing will work on servers defined in the worker.properties file that are also available. If workers are defined for Servoy Application Servers that are not started, disable them from the jkmanager page in order to avoid delays caused by load-balancer trying to check the availability of these workers.
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