JAML

Java Application Monitoring Library (JAML). JAML was designed to be developer and tester friendly library. Current tools and libraries requires either end users to buy the license or write custom code blocks to monitor the application.

Focus of the JAML is to minimum configuration and maximum output.

Features

This library allows users to monitor three types of monitors in the application,

1. Execution time - This allows users to monitor the method execution time
2. Method invocation count - This allows users to monitor method invocation count
3. Variables at various lines - This allows users to log variables at specified line number

Note: As of now, only one type of monitor info can be added per method.

How to use

Currently there are 2 ways JAML can be used,

• Input file
• JMX client (jconsole)
• In built server (Though you will find code for this in the repo but I am not working on this anymore.)

For both of these options, JAML agent must be configured in Java application startup.

Input file

This method uses the Java agent arugment string to accept the name of the file which should be used as source for monitoring the classes. classfile is the name of the argument which should be specified to use this option.

For example, following agent string specifies that JAML library should be loaded from path /opt/jaml/jaml.jar and classes.txt file at /opt/jaml location should be used as the source for the classes to be monitored.

-javaagent:/opt/jaml/jaml.jar=classfile:/opt/jaml/classes.txt

Input file format

Input file should contain the list of classes with comma separated list of methods.

E.g. Following line will monitor only method1ToMonitor,method2ToMonitor methods

com.app.package.ClassName=method1ToMonitor,method2ToMonitor

Following line will monitor all the methods from this class

com.app.package.OtherClass

Execution time monitor info

To monitor method execution time, use following syntax -

com.app.package.ClassName=exec:method2ToMonitor

Note that default monitor info is execution time monitor info, so if you don’t specify “exec:” prefix then also execution time monitor info will be used.

If you have 2 methods with the same name or you want to check what are the parameter values those are passed to this method, you can print the method parameters using following syntax,

com.app.package.ClassName=exec:method2ToMonitor(printVars)

Invocation counter monitor info

To monitor method invocation count, use following syntax -

com.app.package.ClassName=invoc:method2ToMonitor

Invocation counter monitor info

To monitor variable value, use following syntax (little bit complicated) -

com.app.package.ClassName=var:method2ToMonitor(myVariable-30)

In above example, variable to be monitored is myVariable and is to be logged at line number 30.

If you want to monitor multiple variables or you want to monitor variable at different lines then following syntax should be used -

com.app.package.ClassName=var:method2ToMonitor(myVariable-30|secondVariable-36)

Note, library will calculate the delta of new lines being added in the code, so line numbers should be specified using the source code as reference.

JMX client (jconsole)

This method allows a JMX client like jConsole to configure the classes to be monitored by the JAML library. As of now this method is more powerful as using this method you can control the classes and methods to be monitored at runtime.

Note that For this method to work JMX must be enabled on the server/target JVM which is to be monitored. For more info about how to enable JMX, check this article.

Output

Once you have configured JAML in your application JAML library will start printing the monitoring logs on standard output stream with [JAML] prefix like an example below,

[JAML-DEBUG] Monitoring class : com.app.package.ClassName
[JAML-DEBUG] Transforming class:com.app.package.ClassName
[JAML] [main] [Execution:com.app.package.ClassName:methodToMonitor:1523368988577:1523368988578:1:Arguments:arg1,arg2]
[JAML] [main] [Variable:com.app.package.ClassName:methodToMonitor:myVariable:1775939031]
[JAML] [main] [Invocation:com.app.package.ClassName:methodToMonitor:2]

Monitoring log is printed in above format where, [Execution:CLASS_NAME:METHOD_NAME:START_TIME:END_TIME:TIME_EXECUTED:Arguments:COMMA_SEPARATE_ARGUMENT_LIST]