Tuning the server

Servoy Application Server Tuning

Java version

Servoy supports both Java 5 and Java 6 (for the server, the clients and developer). Java 6 has numerous performance improvements, so it is preferred over Java 5.

When the hardware of the Servoy is 64bit, make sure to also run a 64 bit Java Virtual Machine. When in doubt which version is used, check the Servoy Admin page, under "Servoy Server Home" > "Servoy Server Status" > "JDK Information":

* 64 bit: java.vm.name=Java HotSpot(TM) 64-Bit Server VM
* 32 bit: java.vm.name=Java HotSpot(TM) Client VM

Java Virtual Machine Server mode

Java has 2 distinct operating modes: client mode and server mode. When running in server mode, the startup of the Java process will take longer and initial execution of code will be slower, but after a while the application will perform faster. The server mode is best suited for the Servoy Application Server.

Whether or not a Java Virtual Machine supports client and/or server mode depends on the hardware, see http://download.oracle.com/javase/6/docs/technotes/guides/vm/server-class.html.

If the JVM supports servermode, it will automatically detect if the machine it is running on is a "capable" machine and automatically run in server or client mode depending. The definition of "capable" may differ from Java version to Java version. For Java 5/6 this means a 2CPU, 2Gb memory machine.

Checking whether or not a Servoy Application Server runs in client or server mode can be seen on the Servoy Admin page, under "Servoy Server Home" > "Servoy Server Status" > "JDK Information":
* Server mode: java.vm.name=Java HotSpot(TM) 64-Bit Server VM
* Client mode: java.vm.name=Java HotSpot(TM) Client VM

It is possible to enforce the Servoy Application Server to run in server mode (assuming the JVM is capable to operate in server mode), an extra startup argument can be added to the startup of the Servoy Application Server.

In servoy_server.sh/bat:

java -server -Djava.awt.headless=true .....

When using the Service wrapper:

# Java Additional Parameters
wrapper.java.additional.1=-Djava.awt.headless=true
wrapper.java.additional.2=-Duser.dir="C:\Users\pbakker\Desktop\tmp servoy\application_server"
wrapper.java.additional.3=-XX:MaxPermSize=128m
wrapper.java.additional.4=-server

Memory

Processes in Java, like the Servoy Application Server, need to be told explicitly the maximum of memory they are allowed to use. This setting, the maximum heap size, is important to adjust to the load the Servoy Application Server is to handle.

The maximum heap size setting is set in {servoy_install}/application_server/servoy_server.sh/.bat, through the "Xmx" setting.

When the Application Server is started as a Service through the setting can be found in {servoy_install}/application_server/service/wrapper.conf, by the name of "wrapper.java.maxmemory".

By default the maximum heap size is set to 256MB. This setting should be changed when:

• The actual used memory is >= 70% of the specified maximum. The actually used memory can be found on the main page of the Admin page, under System Information, like: Heap memory: allocated=549184K, used=371473K, max=699072K
• When the expected client load will exceed the maximum: As a rule of thumb:
  • Smart Client: assume a memory usage of about 300kb for each Smart Client. NOTE: When the Servoy HTTP Tunnel is used, assume 600kb per Client.
  • All other type of Clients (Web, Headless, Batch): the required memory for each client depends on the size and design of the solution, but should be in the order of magnitude of a couple of Mb per Client.

Web Client Tuning

servoy.webclient.templates.use_local_ids

For the Web Client, Servoy generates HTML markup. In order for Servoy to dynamically update only parts of the UI through Ajax, each object in the HTML Markup receives a unique ID. This ID is also placed in the editable Web Client templates.

Servoy has 2 modes for generating the ID's:

• Using unique identifiers that are part of the internal design of the Solution created with Servoy. These ID's, as they are part of the solution design, are the same on any Servoy Application Server where the solution is imported. 
• Using local identifiers. These identifiers are generated at runtime and thus differ per installation and session.

The advantage of the local identifiers are that they are shorter in length, thus bring down the weight of the generated HTML markup. The advantage of the unique identifiers is that they are the same on any server where the solution is running.

If templates are used to modify the generated HTML markup for Web Clients, then the unique identifiers are to be used, in order to maintain the link between the identifiers in the edited templates and the identifiers used at runtime. Otherwise the local identifiers can be used.

By default a Servoy Application Server uses the unique identifiers. Enabling the use of local identifiers can be done by setting the servoy.webclient.templates.use_local_ids option on the Servoy Admin page to true (located under Servoy Settings > Web Client settings) 

Content compression

In order to minimize the size of the content that the browser has to download for the Web Client, it's possible to turn on compression. The Servoy Application Server is currently not configured to automatically compress the content. 

Compression can be done by the Apache Tomcat instance that is part of the Servoy Application Server, or can be done by an HTTP server that is in front of the Servoy application Server, like an Apache HTTPD Server. 

In order to enable compression in the Tomcat instance that is part of the Servoy Application Server, open the file "server.xml" located in {servoy_install}application_server\server\conf\. and locate the Connector:

<Connector port="8080"
  protocol="HTTP/1.1"
  maxThreads="500" connectionTimeout="60000"
  redirectPort="8443" useBodyEncodingForURI="true" />

and add the following atttributes:

• compressableMimeType="text/html,text/xml,text/css,text/javascript,text/plain" 
• compression="on"
• compressionMinSize="2048" 
• noCompressionUserAgents="gozilla, traviata"

so the connector is configured like this:

<Connector port="8080"
  protocol="HTTP/1.1"
  maxThreads="500" connectionTimeout="60000"
  redirectPort="8443" useBodyEncodingForURI="true"
  compressableMimeType="text/html,text/xml,text/css,text/javascript,text/plain" compression="on"
  compressionMinSize="2048"/>

Save the edits and restart the Servoy Application Server to let the configuration changes take effect.

It is also possible to handle the compression outside of the Servoy Application Server, for example in an Apache HTTPD Server placed between the Servoy Application Server and the outside world. The advantage of this is that Tomcat's compression options are limited, so an external HTTP server offers more options.

When it comes to Apache HTTPD server, there are two options:

1. Compression using mod_deflate
2. Compression using gzip

When it comes to compression, there are two factors that come into play, the time it takes to do the actual compression and the rate of compression achieved, resulting in quicker downloads to the browser due to smaller size. This is primary difference between mod_deflate and gzip in Apache HTTPD: while gzip gets a better compression rate than mod_deflate, it takes more time and CPU to perform the compression. In the case of Servoy Web Clients, that, due to it's Ajax driven design, performs a lot (albeit small) requests to the server, the overall performance will be better using mod_deflate.

Details on setting up mod_deflate on an Apache HTTPD server can be found here: http://httpd.apache.org/docs/2.0/mod/mod_deflate.html