FriendlySNMP JVM management and monitoring
JVM plugin is an optional FriendlySNMP agent plugin. It is loaded if the following parameter is present in configuration:

snmp.plugin.jvm=org.friendlysnmp.plugin.jvm.PluginJVM

The plugin provides access to various JVM data declared in the JVM-MANAGEMENT-MIB. This MIB has minor modification made by Frank Fock. The original JVM Management MIB is available here.

The plugin's code is a trivial bulky routine code to access JVM MBeans and map their values to scalars and tables declared in JVM-MANAGEMENT-MIB. The following MBeans are used:

• java.lang.management.ClassLoadingMXBean
• java.lang.management.CompilationMXBean
• java.lang.management.GarbageCollectorMXBean
• java.lang.management.MemoryMXBean
• java.lang.management.MemoryManagerMXBean
• java.lang.management.MemoryPoolMXBean
• java.lang.management.OperatingSystemMXBean
• java.lang.management.RuntimeMXBean
• java.lang.management.ThreadMXBean

The following arguments should be specified in the command line to initialize JVM built-in SNMP agent (ports could be any):

-Dcom.sun.management.snmp.port=161
-Dcom.sun.management.snmp.trap=162

The JVM reads Access Control List file at startup. See details how to prepare this file below.

ACL file preparation
ACL file must be located at JRE_HOME/lib/management/snmp.acl and prepared in advance. You could use file JRE_HOME/lib/management/snmp.acl.template as a template. Add the following lines at the end of the template file for the testing on localhost:

acl = {
  {
    communities = public, private
    access = read-write
    managers = localhost
  }
}
trap = {
  {
    trap-community = public
    hosts = localhost
  }
}

Error: Password file read access must be restricted: C:\\lib\management\snmp.acl
ACL file must be readable only by owner. It’s OK to allow read/write to the acl-file on WinXP with a single owner. Use command: "cacls filename /P username:R" to secure a file. See discussion how to use this command here. The same result could be achieved by changing properties of this file (on WinXP):

1. Open snmp.acl file properties.
2. Go to the tab Security.
3. Click button Advanced.
4. Go to the tab Permissions and uncheck inherit with copy from parent.
5. Go to the tab Permissions and remove all users, except a single one with current login.
6. Go to the tab Owner and select current owner.
7. Click button Apply.

Which one to use?
Both FriendlySNMP and Sun's built-in JVM management and monitoring has pros and cons.

FriendlySNMP JVM management and monitoring plugin should be preferred if FriendlySNMP agent is created and initialized in the application. This JVM plugin requires minimal additional memory and does not require ports allocation.

Sun's SNMP JVM management and monitoring should be preferred if the application does not have FriendlySNMP agent.