JVM Garbage Collections Test

Manual memory management is time consuming, and error prone. Most programs still contain leaks. This is all doubly true with programs using exception-handling and/or threads. Garbage collection (GC) is a part of a Java application’s JVM that automatically determines what memory a program is no longer using, and recycles it for other use. It is also known as "automatic storage (or memory) reclamation''.  The JVM Garbage Collections test reports the performance statistics pertaining to the JVM's garbage collection.

Target of the test : A Java application

Agent deploying the test : An internal/remote agent

Outputs of the test : One set of results for each garbage collector that is reclaiming the unused memory on the JVM of the Java application being monitored.

Configurable parameters for the test
Parameter Description

Test Period

How often should the test be executed.

Host

The IP address of the host for which this test is to be configured.

Port

Refers to the port at which the specified host listens to.

Mode

This test can extract metrics from the Java application using either of the following mechanisms:

  • Using SNMP-based access to the Java runtime MIB statistics;
  • By contacting the Java runtime (JRE) of the application via JMX

To configure the test to use SNMP, select the SNMP option. On the other hand, choose the JMX option to configure the test to use JMX instead. By default, the JMX option is chosen here.

JMX Remote Port

This parameter appears only if the Mode is set to JMX. Here, specify the port at which the JMX listens for requests from remote hosts. Ensure that you specify the same port that you configured in the management.properties file in the <JAVA_Home>\jre\lib\management folder used by the target application (refer to the Monitoring Java Applications for details).

User, Password, and Confirm Password

These parameters appear only if the Mode is set to JMX. If JMX requires authentication only (but no security), then ensure that the User and Password parameters are configured with the credentials of a user with read-write access to JMX. To know how to create this user, refer to the Monitoring Java Applications. Confirm the password by retyping it in the Confirm Password text box.

JNDIName

This parameter appears only if the Mode is set to JMX. The JNDIName is a lookup name for connecting to the JMX connector. By default, this is jmxrmi. If you have registered the JMX connector in the RMI registery using a different lookup name, then you can change this default value to reflect the same. 

JMX Provider

This parameter appears only if the Mode is set to JMX. This test uses a JMX Provider to access the MBean attributes of the target Java application and collect metrics. Specify the package name of this JMX Provider here. By default, this is set to com.sun.jmx.remote.protocol.

Timeout

Specify the duration (in seconds) for which this test should wait for a response from the target Java application. If there is no response from the target beyond the configured duration, the test will timeout. By default, this is set to 240 seconds if the mode is JMX, and 10 seconds if the mode is SNMP.

SNMPPort

This parameter appears only if the Mode is set to SNMP. Here specify the port number through which the server exposes its SNMP MIB. Ensure that you specify the same port you configured in the management.properties file in the <JAVA_HOME>\jre\lib\management folder used by the target application (refer to the Monitoring Java Applications for details).

SNMPVersion

This parameter appears only if the Mode is set to SNMP. By default, the eG agent supports SNMP version 1. Accordingly, the default selection in the SNMPversion list is v1. However, if a different SNMP framework is in use in your environment, say SNMP v2 or v3, then select the corresponding option from this list.

SNMPCommunity

This parameter appears only if the Mode is set to SNMP. The SNMP community name that the test uses to communicate with the firewall. This parameter is specific to SNMP v1 and v2 only. Therefore, if the SNMPVersion chosen is v3, then this parameter will not appear.

UserName

This parameter appears only when v3 is selected as the SNMPVersion. SNMP version 3 (SNMPv3) is an extensible SNMP Framework which supplements the SNMPv2 Framework, by additionally supporting message security, access control, and remote SNMP configuration capabilities. To extract performance statistics from the MIB using the highly secure SNMP v3 protocol, the eG agent has to be configured with the required access privileges – in other words, the eG agent should connect to the MIB using the credentials of a user with access permissions to be MIB. Therefore, specify the name of such a user against this parameter. 

Context

This parameter appears only when v3 is selected as the SNMPVersion. An SNMP context is a collection of management information accessible by an SNMP entity. An item of management information may exist in more than one context and an SNMP entity potentially has access to many contexts. A context is identified by the SNMPEngineID value of the entity hosting the management information (also called a contextEngineID) and a context name that identifies the specific context (also called a contextName). If the Username provided is associated with a context name, then the eG agent will be able to poll the MIB and collect metrics only if it is configured with the context name as well. In such cases therefore, specify the context name of the UserName in the Context text box.  By default, this parameter is set to none.

AuthPass

Specify the password that corresponds to the above-mentioned UserName. This parameter once again appears only if the SNMPversion selected is v3.

Confirm Password

Confirm the AuthPass by retyping it here.

AuthType

This parameter too appears only if v3 is selected as the SNMPVersion. From the AuthType list box, choose the authentication algorithm using which SNMP v3 converts the specified username and password into a 32-bit format to ensure security of SNMP transactions. You can choose between the following options:

  • MD5 – Message Digest Algorithm
  • SHA – Secure Hash Algorithm

EncryptFlag

This flag appears only when v3 is selected as the SNMPVersion. By default, the eG agent does not encrypt SNMP requests. Accordingly, the this flag is set to No by default. To ensure that SNMP requests sent by the eG agent are encrypted, select the Yes option. 

EncryptType

If this EncryptFlag is set to Yes, then you will have to mention the encryption type by selecting an option from the EncryptType list. SNMP v3 supports the following encryption types:

  • DES – Data Encryption Standard
  • AES – Advanced Encryption Standard

EncryptPassword

Specify the encryption password here.

Confirm Password

Confirm the encryption password by retyping it here.

Data Over TCP

This parameter appears only if the Mode is set to SNMP. By default, in an IT environment, all data transmission occurs over UDP. Some environments however, may be specifically configured to offload a fraction of the data traffic – for instance, certain types of data traffic or traffic pertaining to specific components – to other protocols like TCP, so as to prevent UDP overloads. In such environments, you can instruct the eG agent to conduct the SNMP data traffic related to the monitored target over TCP (and not UDP). For this, set this flag to Yes. By default, this flag is set to No.
Measurements made by the test
Measurement Description Measurement Unit Interpretation

No of garbage collections started

Indicates the number of times this garbage collector was started to release dead objects from memory during the last measurement period.

Number

 

Time taken for garbage collection

Indicates the time taken to by this garbage collector to perform the current garbage collection operation.

Secs

Ideally, the value of both these measures should be low. This is because, the garbage collection (GC) activity tends to suspend the operations of the application until such time that GC ends. Longer the GC time, longer it would take for the application to resume its functions. To minimize the impact of GC on application performance, it is best to ensure that GC activity does not take too long to complete.

Percent of time spent by JVM for garbage collection

Indicates the percentage of time spent by this garbage collector on garbage collection during the last measurement period.

Percent