RR4J [Record Replay 4 Java]

Build Requirements

1. C++ 11
2. Java 8
3. make
4. maven

Building Record Agent

1. Navigate to recordagent folder
2. Run make all command

Building Replay Agent

1. Navigate to replayagent folder
2. Run make all command

Building Java code

1. Run mvn clean install

Record Agent Configuration

Once the build is completed you need to configure the record agent, this can be done through config.json file and the file should be in the same place the agent is. Below is a sample configuration.

{
	"logFileName": "record.log",
	"logFileMaxSize": 100000,
	"maxLogFiles": 2,
	"recordDumpLocation":"",
	"delayedStart":5000,
	"recordCallerSnapshot": true,
	"blacklistPackages":["java/lang","sun/reflect","java/util", "java/io"],
	"rules": [
		{
			"method": "com/example/Test::MethodHasBug(IILjava/lang/String;)Ljava/lang/String;",
			"exception": "java.lang.NullPointerException",
			"additivity": false,
			"exitOnException": true,
			"threadsToMonitor" :1,
			"depth":2,
			"history":10,
			"threadsToRecord":10
		}
	]
}

Example :
methodA() --> Calls --↓
                     methodB() --> Calls --↓
                                          methodC()

Example

Recording the execution

Consider a simple java code, where I want to record a methodA(long time) execution. I will configure my record agent to record 3 iterations with below config values.

"method": "Dummy::methodA(J)I",
"exception": "",
"additivity": false,
"exitOnException": false,
"threadsToMonitor" :1,
"depth":2,
"history":3,
"threadsToRecord":1

class Dummy
{
	int methodA(long time)
	{
		String sTime = String.valueOf(time);
		int val = methodB(sTime);
		return val-1;
		
	}
	
	int methodB(String s)
	{
		int x = methodC().length();
		return s.length()-x;
	}
	
	String methodC()
	{
		String x = "hello world";
		return x;
	}
	
}

public class TestClass
{

	public static void main(String[] args) 
	{
		Dummy d = new Dummy();
		for(int i=0; i<30; i++)
		{
			try {Thread.sleep(1000);} catch(Exception ex) {}
			d.methodA(System.currentTimeMillis());
		}
	}

}

Once done, Start a program with the below command.

export LD_LIBRARY_PATH=<path/to/record/agent/so/file>
java -cp recordreplay-0.0.1-SNAPSHOT-jar-with-dependencies.jar:**TestClass class file path** -agentlib:recordagent TestClass

Post this you will see a dump file generated with the name recordDump-.dmp which can be passed as input during replay mode.

Replaying the execution

Run the following command to start the tool in replay mode.

export LD_LIBRARY_PATH=<path/to/replay/agent/so/file>
java -agentlib:replayagent -cp recordreplay-0.0.1-SNAPSHOT-jar-with-dependencies.jar:**TestClass class file path** com.rr4j.replay.Replay --dumpFile recordDump.dmp

You will see an interactor, you can also add -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=8000 to start the debugger and attach an IDE.

To list all records use '-a' command

You can add a breakpoint in IDE and use '-rs recordIndex' to replay the particular record.

Future scope

1. Record thread state to provide a detailed breakdown, mimic race conditions.
2. Lamda function support.
3. Dynamic class support generated on the fly by ASM and other libraries.
4. Support controlling execution flow, recording only the particular path through line numbers.