Servoy 2020 Documentation
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When the Maximum Heap Space size is too low for that is actually needed by the Java process, the following exception will be thrown: java.lang.OutOfMemoryError: Java heap space

Java Perm Space (java 7)

The Perm Space is the space used by Java to store loaded classes and other static objects. The setting related to the Java Perm Space is only the following.

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(warning)  The above mentioned settings are settings that can be applied when launching a Java process command-line or form a .bat/.sh script. Certain application might provide other ways to specify the same settings, for example the Service component that is part of the Servoy distribution. For more information on how to configure these settings withing Servoy, read the next paragraph.

 

Java metaspace (java 8 and higher, replacement of the java 7 perm space above)

Java 8 changed the way it stored classes and is using now native memory for that instead of a special java heap

these settings can be adjusted by using the following vm arguments:

-XX:MetaspaceSize=200M -XX:MaxMetaspaceSize=200M -XX:MinMetaspaceFreeRatio=0 -XX:MaxMetaspaceFreeRatio=100 

 

this sets it to use 200MB for that if you get a java.lang.OutOfMemoryError: metaspace because a lot of plugins are used then you need to update that value to something higher like 300/400.

Server Memory Management

Memory management for a Servoy Application Server revolves around managing the values for the Java Heap Space and Java Perm Space.

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  • Java Heap Space: 1280Mb
  • Java Perm Space: 128Mb (java7)
  • Java meta space: 200Mb (java8+)

Depending on how the Servoy Application Server is launched, the location where these values can be managed differs:

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When using the Service component to automatically launch the Servoy Application Server when the machine on which it is installed is booted, the memory settings for the Application Server can be configured inside {serverInstall}\application_server\service\wrapper.conf by altering the wrapper.java.maxmemory setting: 

Code Block
wrapper.java.additional.5=-XX:MetaspaceSize=200M
wrapper.java.additional.6=-XX:MaxMetaspaceSize=200M
wrapper.java.additional.7=-XX:MinMetaspaceFreeRatio=0
wrapper.java.additional.48=-XX:MaxMetaspaceFreeRatio=100 
wrapper.java.additional.9=-XX:MaxPermSize=128m
wrapper.java.additional.10=-XX:+UseG1GC
# make sure that the hardcoded System.gc() or Runtime.gc() are ignored (rmi does this)
wrapper.java.additional.11=-XX:+DisableExplicitGC
# Initial Java Heap Size (in MB), when G1GC is used just set the init memory to the max memory
wrapper.java.initmemory=321280  
# Maximum Java Heap Size (in MB)
wrapper.java.maxmemory=1280

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Code Block
java ... -Djava.awt.headless=true -Xmx1280m -Xms64m -XX:MetaspaceSize=200M -XX:MaxMetaspaceSize=200M -XX:MinMetaspaceFreeRatio=0 -XX:MaxPermSizeMaxMetaspaceFreeRatio=128m100  .....


Note
titleSpecifying -Xmx and -Xms values

When specifying the -Xmx and -Xms values, the following needs to be taken into account:

  • The value can only be an integer value
  • The value needs to be places directly behind the parameter, no spaces or equal signs
  • The value needs to be post fixed with the unit: 'm' or 'M' for megabytes, 'g' or 'G' for gigabytes
  • When changing the -Xms options,  make sure that the -Xmx option has a higher value
  • Both values need to be lower than the available memory on the machine

In a default Servoy Application Server installation, the Maximum Heap Space value (-Xmx) is set to 1280m. For servers that have limited memory, this value could be too high, resulting in the following error when trying to start the server:

Code Block
Error occurred during initialization of VM
Could not reserve enough space for object heap
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.

Either lower the -Xmx value or make sure that more memory is available for the Java process on the server, by closing other applications or adding more physical memory to the server.

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(warning)   An 32 bit JVM will allow a maximum memory assignment of 2Gb in total. In order to assign more than 2Gb of memory, a 64 bit JVM on a 64 bit OS is required.

Determining the Required Java Metaspace or Perm Space Value

By default the Java Heap Space size is set to 128Mb/200Mb, which is a sufficient value for most deployments. A scenario in which this value needs increasing is when the Servoy Application Server is loaded up with a lot of additional plugins, beans, LAF's and drivers.

Configuring the Java Perm/Metaspace Space Value

For all three scenario's that the Servoy Application Server can be started (as a service, manual stand-alone or manual clustered), the value for the Java Perm Space is controlled by the 'XX:MaxPermSize' setting in the above mentioned configuration location .for java 7 or for java 8:

-XX:MetaspaceSize=200M -XX:MaxMetaspaceSize=200M -XX:MinMetaspaceFreeRatio=0 -XX:MaxMetaspaceFreeRatio=100 

Monitoring the Memory Usage

The actual memory usage of a Servoy Application Server can be observed on the Servoy Admin page. The 'Servoy Server Status' overview on the 'Servoy Server Home' page displays the allocated, used and maximum values for the Heap memory and all other spaces combined (non-Heap memory).

Or through Monitoring Servoy with JMX

 

Running big servers with big heaps for many Web/NGClients

For large heaps (more then 4G) that needs to handle quite a lot of Web or NGClients the vm needs some tuning to be able to handle this nicely.

Use the latest Java 8 and use the G1 Garbagabe collector for this and make sure that the initial heap and the maximum heap ist just set to the same value:

-server -Xms4G -Xmx4G -XX:+UseG1GC -XX:MetaspaceSize=200M -XX:MaxMetaspaceSize=200M -XX:MinMetaspaceFreeRatio=0 -XX:MaxMetaspaceFreeRatio=100 -XX:+DisableExplicitGC

 

Where the 4G for the initial (Xms) and the max (Xmx) should be set to the maximum heap you want or can assign to the java vm.

Smart Client Memory Management

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