Category Archives: JAVA

Print stacktraces for all threads on shutdown

April 22, 2020debugging, JAVA, JVM, Scalatobias

If your microservice stops responding from time to time, and they only way out is to kill it with SIGINT or SIGTERM then adding a shutdown hook might be the way to go. Do note that this will not work if you kill the process with SIGKILL (-9), cause that will result in an unclean shutdown.

Some of this code is heavily influenced by Print all of the thread’s information and stack traces : Exception « Development « Java Tutorial. But has been translated into Scala, and cleaned up a little.

import java.io.PrintWriter
import java.lang.management.ManagementFactory

object TryOutShutdownHook {


  def doStuff() = {
    (1 to 1000).foreach( _ => {
      print(".")
      Thread.sleep(1000)
    })
  }


  def main(args: Array[String]): Unit = {
    sys.addShutdownHook({
      println("Shutdown hook!")
      ThreadUtils.printThreadInfo(new PrintWriter(System.out),"Threads during shutdown")
    })

    doStuff()

  }
}



object ThreadUtils {

  private val threadBean = ManagementFactory.getThreadMXBean

  def setContentionTracing(on: Boolean): Unit = {
    threadBean.setThreadContentionMonitoringEnabled( on )
  }

  private def getTaskName(id: Long, name: String): String = {
    if (name == null) id.toString
    else id + " (" + name + ")"
  }

  /**
   * Print all of the thread's information and stack traces.
   *
   * @param stream
   * the stream to
   * @param title
   * a string title for the stack trace
   */
  def printThreadInfo(stream: PrintWriter, title: String): Unit = {
    val STACK_DEPTH = 20
    val contention = threadBean.isThreadContentionMonitoringEnabled
    val threadIds = threadBean.getAllThreadIds
    stream.println("Process Thread Dump: " + title)
    stream.println(threadIds.length + " active threads")
    for (tid <- threadIds) {
      val info = threadBean.getThreadInfo(tid, STACK_DEPTH)
      if (info == null) {
        stream.println("  Inactive")
      } else {
        stream.println("Thread " + getTaskName(info.getThreadId, info.getThreadName) + ":")
        val state = info.getThreadState
        stream.println("  State: " + state)
        stream.println("  Blocked count: " + info.getBlockedCount)
        stream.println("  Waited count: " + info.getWaitedCount)
        if (contention) {
          stream.println("  Blocked time: " + info.getBlockedTime)
          stream.println("  Waited time: " + info.getWaitedTime)
        }
        if (state eq Thread.State.WAITING) stream.println("  Waiting on " + info.getLockName)
        else if (state eq Thread.State.BLOCKED) {
          stream.println("  Blocked on " + info.getLockName)
          stream.println("  Blocked by " + getTaskName(info.getLockOwnerId, info.getLockOwnerName))
        }
        stream.println("  Stack:")
        for (frame <- info.getStackTrace) {
          stream.println("    " + frame.toString)
        }
      }
    }
    stream.flush()
  }
}

import java.io.PrintWriter

import java.lang.management.ManagementFactory

object TryOutShutdownHook {

def doStuff() = {

(1 to 1000).foreach( _ => {

print(".")

Thread.sleep(1000)

})

}

def main(args: Array[String]): Unit = {

sys.addShutdownHook({

println("Shutdown hook!")

ThreadUtils.printThreadInfo(new PrintWriter(System.out),"Threads during shutdown")

})

doStuff()

}

object ThreadUtils {

private val threadBean = ManagementFactory.getThreadMXBean

def setContentionTracing(on: Boolean): Unit = {

threadBean.setThreadContentionMonitoringEnabled( on )

}

private def getTaskName(id: Long, name: String): String = {

if (name == null) id.toString

else id + " (" + name + ")"

}

/**

* Print all of the thread's information and stack traces.

* @param stream

* the stream to

* @param title

* a string title for the stack trace

def printThreadInfo(stream: PrintWriter, title: String): Unit = {

val STACK_DEPTH = 20

val contention = threadBean.isThreadContentionMonitoringEnabled

val threadIds = threadBean.getAllThreadIds

stream.println("Process Thread Dump: " + title)

stream.println(threadIds.length + " active threads")

for (tid <- threadIds) {

val info = threadBean.getThreadInfo(tid, STACK_DEPTH)

if (info == null) {

stream.println(" Inactive")

} else {

stream.println("Thread " + getTaskName(info.getThreadId, info.getThreadName) + ":")

val state = info.getThreadState

stream.println(" State: " + state)

stream.println(" Blocked count: " + info.getBlockedCount)

stream.println(" Waited count: " + info.getWaitedCount)

if (contention) {

stream.println(" Blocked time: " + info.getBlockedTime)

stream.println(" Waited time: " + info.getWaitedTime)

}

if (state eq Thread.State.WAITING) stream.println(" Waiting on " + info.getLockName)

else if (state eq Thread.State.BLOCKED) {

stream.println(" Blocked on " + info.getLockName)

stream.println(" Blocked by " + getTaskName(info.getLockOwnerId, info.getLockOwnerName))

}

stream.println(" Stack:")

for (frame <- info.getStackTrace) {

stream.println(" " + frame.toString)

}

stream.flush()

}

The output would look something like this

...........................Shutdown hook!
Process Thread Dump: Threads during shutdown
8 active threads
Thread 11 (shutdownHook1):
  State: RUNNABLE
  Blocked count: 0
  Waited count: 0
  Stack:
    sun.management.ThreadImpl.getThreadInfo1(Native Method)
    sun.management.ThreadImpl.getThreadInfo(ThreadImpl.java:178)
    sun.management.ThreadImpl.getThreadInfo(ThreadImpl.java:139)
    ThreadUtils$.$anonfun$printThreadInfo$1(TryOutShutdownHook.scala:56)
    ThreadUtils$$$Lambda$7/1354382162.apply$mcVJ$sp(Unknown Source)
    scala.runtime.java8.JFunction1$mcVJ$sp.apply(JFunction1$mcVJ$sp.java:23)
    scala.collection.IndexedSeqOptimized.foreach(IndexedSeqOptimized.scala:36)
    scala.collection.IndexedSeqOptimized.foreach$(IndexedSeqOptimized.scala:33)
    scala.collection.mutable.ArrayOps$ofLong.foreach(ArrayOps.scala:258)
    ThreadUtils$.printThreadInfo(TryOutShutdownHook.scala:55)
    TryOutShutdownHook$.$anonfun$main$1(TryOutShutdownHook.scala:18)
    TryOutShutdownHook$$$Lambda$1/728890494.apply$mcV$sp(Unknown Source)
    scala.sys.ShutdownHookThread$$anon$1.run(ShutdownHookThread.scala:37)
Thread 13 (SIGTERM handler):
  State: WAITING
  Blocked count: 0
  Waited count: 1
  Waiting on scala.sys.ShutdownHookThread$$anon$1@506c589e
  Stack:
    java.lang.Object.wait(Native Method)
    java.lang.Thread.join(Thread.java:1252)
    java.lang.Thread.join(Thread.java:1326)
    java.lang.ApplicationShutdownHooks.runHooks(ApplicationShutdownHooks.java:107)
    java.lang.ApplicationShutdownHooks$1.run(ApplicationShutdownHooks.java:46)
    java.lang.Shutdown.runHooks(Shutdown.java:123)
    java.lang.Shutdown.sequence(Shutdown.java:167)
    java.lang.Shutdown.exit(Shutdown.java:212)
    java.lang.Terminator$1.handle(Terminator.java:52)
    sun.misc.Signal$1.run(Signal.java:212)
    java.lang.Thread.run(Thread.java:748)
Thread 12 (Attach Listener):
  State: RUNNABLE
  Blocked count: 0
  Waited count: 0
  Stack:
Thread 5 (Monitor Ctrl-Break):
  State: RUNNABLE
  Blocked count: 0
  Waited count: 0
  Stack:
    java.net.SocketInputStream.socketRead0(Native Method)
    java.net.SocketInputStream.socketRead(SocketInputStream.java:116)
    java.net.SocketInputStream.read(SocketInputStream.java:171)
    java.net.SocketInputStream.read(SocketInputStream.java:141)
    sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:284)
    sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:326)
    sun.nio.cs.StreamDecoder.read(StreamDecoder.java:178)
    java.io.InputStreamReader.read(InputStreamReader.java:184)
    java.io.BufferedReader.fill(BufferedReader.java:161)
    java.io.BufferedReader.readLine(BufferedReader.java:324)
    java.io.BufferedReader.readLine(BufferedReader.java:389)
    com.intellij.rt.execution.application.AppMainV2$1.run(AppMainV2.java:64)
Thread 4 (Signal Dispatcher):
  State: RUNNABLE
  Blocked count: 0
  Waited count: 0
  Stack:
Thread 3 (Finalizer):
  State: WAITING
  Blocked count: 1
  Waited count: 2
  Waiting on java.lang.ref.ReferenceQueue$Lock@79c01878
  Stack:
    java.lang.Object.wait(Native Method)
    java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:144)
    java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:165)
    java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:216)
Thread 2 (Reference Handler):
  State: WAITING
  Blocked count: 1
  Waited count: 1
  Waiting on java.lang.ref.Reference$Lock@2b1227e6
  Stack:
    java.lang.Object.wait(Native Method)
    java.lang.Object.wait(Object.java:502)
    java.lang.ref.Reference.tryHandlePending(Reference.java:191)
    java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153)
Thread 1 (main):
  State: TIMED_WAITING
  Blocked count: 0
  Waited count: 27
  Stack:
    java.lang.Thread.sleep(Native Method)
    TryOutShutdownHook$.$anonfun$doStuff$1(TryOutShutdownHook.scala:10)
    TryOutShutdownHook$$$Lambda$6/2047526627.apply$mcVI$sp(Unknown Source)
    scala.collection.immutable.Range.foreach$mVc$sp(Range.scala:158)
    TryOutShutdownHook$.doStuff(TryOutShutdownHook.scala:8)
    TryOutShutdownHook$.main(TryOutShutdownHook.scala:21)
    TryOutShutdownHook.main(TryOutShutdownHook.scala)

Process finished with exit code 143 (interrupted by signal 15: SIGTERM)

...........................Shutdown hook!

Process Thread Dump: Threads during shutdown

8 active threads

Thread 11 (shutdownHook1):

State: RUNNABLE

Blocked count: 0

Waited count: 0

Stack:

sun.management.ThreadImpl.getThreadInfo1(Native Method)

sun.management.ThreadImpl.getThreadInfo(ThreadImpl.java:178)

sun.management.ThreadImpl.getThreadInfo(ThreadImpl.java:139)

ThreadUtils$.$anonfun$printThreadInfo$1(TryOutShutdownHook.scala:56)

ThreadUtils$$$Lambda$7/1354382162.apply$mcVJ$sp(Unknown Source)

scala.runtime.java8.JFunction1$mcVJ$sp.apply(JFunction1$mcVJ$sp.java:23)

scala.collection.IndexedSeqOptimized.foreach(IndexedSeqOptimized.scala:36)

scala.collection.IndexedSeqOptimized.foreach$(IndexedSeqOptimized.scala:33)

scala.collection.mutable.ArrayOps$ofLong.foreach(ArrayOps.scala:258)

ThreadUtils$.printThreadInfo(TryOutShutdownHook.scala:55)

TryOutShutdownHook$.$anonfun$main$1(TryOutShutdownHook.scala:18)

TryOutShutdownHook$$$Lambda$1/728890494.apply$mcV$sp(Unknown Source)

scala.sys.ShutdownHookThread$$anon$1.run(ShutdownHookThread.scala:37)

Thread 13 (SIGTERM handler):

State: WAITING

Blocked count: 0

Waited count: 1

Waiting on scala.sys.ShutdownHookThread$$anon$1@506c589e

Stack:

java.lang.Object.wait(Native Method)

java.lang.Thread.join(Thread.java:1252)

java.lang.Thread.join(Thread.java:1326)

java.lang.ApplicationShutdownHooks.runHooks(ApplicationShutdownHooks.java:107)

java.lang.ApplicationShutdownHooks$1.run(ApplicationShutdownHooks.java:46)

java.lang.Shutdown.runHooks(Shutdown.java:123)

java.lang.Shutdown.sequence(Shutdown.java:167)

java.lang.Shutdown.exit(Shutdown.java:212)

java.lang.Terminator$1.handle(Terminator.java:52)

sun.misc.Signal$1.run(Signal.java:212)

java.lang.Thread.run(Thread.java:748)

Thread 12 (Attach Listener):

State: RUNNABLE

Blocked count: 0

Waited count: 0

Stack:

Thread 5 (Monitor Ctrl-Break):

State: RUNNABLE

Blocked count: 0

Waited count: 0

Stack:

java.net.SocketInputStream.socketRead0(Native Method)

java.net.SocketInputStream.socketRead(SocketInputStream.java:116)

java.net.SocketInputStream.read(SocketInputStream.java:171)

java.net.SocketInputStream.read(SocketInputStream.java:141)

sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:284)

sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:326)

sun.nio.cs.StreamDecoder.read(StreamDecoder.java:178)

java.io.InputStreamReader.read(InputStreamReader.java:184)

java.io.BufferedReader.fill(BufferedReader.java:161)

java.io.BufferedReader.readLine(BufferedReader.java:324)

java.io.BufferedReader.readLine(BufferedReader.java:389)

com.intellij.rt.execution.application.AppMainV2$1.run(AppMainV2.java:64)

Thread 4 (Signal Dispatcher):

State: RUNNABLE

Blocked count: 0

Waited count: 0

Stack:

Thread 3 (Finalizer):

State: WAITING

Blocked count: 1

Waited count: 2

Waiting on java.lang.ref.ReferenceQueue$Lock@79c01878

Stack:

java.lang.Object.wait(Native Method)

java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:144)

java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:165)

java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:216)

Thread 2 (Reference Handler):

State: WAITING

Blocked count: 1

Waited count: 1

Waiting on java.lang.ref.Reference$Lock@2b1227e6

Stack:

java.lang.Object.wait(Native Method)

java.lang.Object.wait(Object.java:502)

java.lang.ref.Reference.tryHandlePending(Reference.java:191)

java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153)

Thread 1 (main):

State: TIMED_WAITING

Blocked count: 0

Waited count: 27

Stack:

java.lang.Thread.sleep(Native Method)

TryOutShutdownHook$.$anonfun$doStuff$1(TryOutShutdownHook.scala:10)

TryOutShutdownHook$$$Lambda$6/2047526627.apply$mcVI$sp(Unknown Source)

scala.collection.immutable.Range.foreach$mVc$sp(Range.scala:158)

TryOutShutdownHook$.doStuff(TryOutShutdownHook.scala:8)

TryOutShutdownHook$.main(TryOutShutdownHook.scala:21)

TryOutShutdownHook.main(TryOutShutdownHook.scala)

Process finished with exit code 143 (interrupted by signal 15: SIGTERM)

UDF/User Defined Functions in Cassandra 3.x

August 11, 2016Cassandra, JAVAtobias

I was just playing around with Cassandra WRITETIME and thought it was somewhat difficult to figure out the date / timestamp of a number like this (microseconds since EPOC) 1470645914253000.

So in my example it looked like this

cqlsh:bth> select id, writetime(dateofbirth) from bth.employee;

 id | writetime(dateofbirth)
----+------------------------
  1 |       1470645914253000
  2 |       1470645977177000
  7 |       1470948508799001
  3 |       1470645977178000

(4 rows)
cqlsh:bth>

cqlsh:bth> select id, writetime(dateofbirth) from bth.employee;

id | writetime(dateofbirth)

----+------------------------

1 | 1470645914253000

2 | 1470645977177000

7 | 1470948508799001

3 | 1470645977178000

(4 rows)

cqlsh:bth>

So I figured why not create a UDF that would solve this for me

That turned out to be a little bit of a challenge …

I thought that I could do like this

CREATE FUNCTION bth.ts2date ( input bigint )
	RETURNS NULL ON NULL INPUT
    RETURNS text 
    LANGUAGE java
    AS $$
    	if( input > 0L ) {
    		long ms = input / 1000L;
    		Date date=new Date(ms);
    		SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss,SSS");
    		return sdf.format(date);
    	} else return null;
    $$;

CREATE FUNCTION bth.ts2date ( input bigint )

RETURNS NULL ON NULL INPUT

RETURNS text

LANGUAGE java

AS $$

if( input > 0L ) {

long ms = input / 1000L;

Date date=new Date(ms);

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss,SSS");

return sdf.format(date);

} else return null;

$$;

BUT NO, YOU CAN NOT!!!

There are several WRONGS in here it turns out

First off you have to turn on
enable_user_defined_functions: true
in the conf/cassandra.yaml file
All classes has to be fully qualified, so Date would be java.util.Date, and so on…
The division operator ‘/’ can not be used !!! however +,- and * works fine. surely this must be a bug … this called for some thinking…

The error I got when trying to use the code above without fully qualified names was

cqlsh> CREATE FUNCTION ts2date ( input bigint )
   ... RETURNS NULL ON NULL INPUT
   ...     RETURNS text 
   ...     LANGUAGE java
   ...     AS $$
   ...     if( input != null ) {
   ...     Date date=new Date(mills);
InvalidRequest: code=2200 [Invalid query] message="Functions must be fully qualified with a keyspace name if a keyspace is not set for the session"

cqlsh> CREATE FUNCTION ts2date ( input bigint )

... RETURNS NULL ON NULL INPUT

... RETURNS text

... LANGUAGE java

... AS $$

... if( input != null ) {

... Date date=new Date(mills);

InvalidRequest: code=2200 [Invalid query] message="Functions must be fully qualified with a keyspace name if a keyspace is not set for the session"

And the reason, if I got it right, is that you can not do imports.

The error I got when trying to use the division ‘/’ operator was this:

cqlsh:bth> CREATE FUNCTION bth.ts2date ( input bigint )
       ... RETURNS NULL ON NULL INPUT
       ...     RETURNS text 
       ...     LANGUAGE java
       ...     AS $$
       ...     if( input > 0L ) {
       ...     java.util.Date date=new java.util.Date(input/1000);
Invalid syntax at line 7, char 49
      java.util.Date date=new java.util.Date(input/1000);
                                                  ^
cqlsh:bth>

cqlsh:bth> CREATE FUNCTION bth.ts2date ( input bigint )

... RETURNS NULL ON NULL INPUT

... RETURNS text

... LANGUAGE java

... AS $$

... if( input > 0L ) {

... java.util.Date date=new java.util.Date(input/1000);

Invalid syntax at line 7, char 49

java.util.Date date=new java.util.Date(input/1000);

cqlsh:bth>

The code that works looks like this, using java.math.BigDecimal to solve it was perhaps a so-so solution, but it works:

CREATE FUNCTION bth.ts2date ( input bigint ) 
RETURNS NULL ON NULL INPUT     
RETURNS text      
LANGUAGE java     
AS $$     
	if( input > 0L ) {     
		java.math.BigDecimal t = java.math.BigDecimal.valueOf(1000L);     
		java.math.BigDecimal inp = java.math.BigDecimal.valueOf(input);     
		java.math.BigDecimal mst = inp.divide(t); 
		long ms = mst.longValue();     
		java.util.Date date=new java.util.Date(ms);     
		java.text.SimpleDateFormat sdf = new java.text.SimpleDateFormat("yyyy-MM-dd HH:mm:ss,SSS");     
		return sdf.format(date);     
	} else return null;     
$$;

CREATE FUNCTION bth.ts2date ( input bigint )

RETURNS NULL ON NULL INPUT

RETURNS text

LANGUAGE java

AS $$

if( input > 0L ) {

java.math.BigDecimal t = java.math.BigDecimal.valueOf(1000L);

java.math.BigDecimal inp = java.math.BigDecimal.valueOf(input);

java.math.BigDecimal mst = inp.divide(t);

long ms = mst.longValue();

java.util.Date date=new java.util.Date(ms);

java.text.SimpleDateFormat sdf = new java.text.SimpleDateFormat("yyyy-MM-dd HH:mm:ss,SSS");

return sdf.format(date);

} else return null;

$$;

So now my output in cqlsh.sh looks like this now

cqlsh:bth> select id, ts2date(writetime(dateofbirth)) from bth.employee;

 id | bth.ts2date(writetime(dateofbirth))
----+-------------------------------------
  1 |             2016-08-08 10:45:14,253
  2 |             2016-08-08 10:46:17,177
  7 |             2016-08-11 22:48:28,799
  3 |             2016-08-08 10:46:17,178

(4 rows)
cqlsh:bth>

cqlsh:bth> select id, ts2date(writetime(dateofbirth)) from bth.employee;

id | bth.ts2date(writetime(dateofbirth))

----+-------------------------------------

1 | 2016-08-08 10:45:14,253

2 | 2016-08-08 10:46:17,177

7 | 2016-08-11 22:48:28,799

3 | 2016-08-08 10:46:17,178

(4 rows)

cqlsh:bth>

That is a lot better !

Cassandra set the writetime explicitly with a PreparedStatement

March 16, 2016Cassandra, JAVA, Scalatobias

This is a quick one, I wanted to set the writetime of a row explicitly when I populate the database for testing purposes. We use the writetime of a column to filter them out.

It required some looking around to find out how to do this…. so I figured I write an article about it.

INSERT INTO invoices (invoice_id,amount,tax,description) VALUES ('333',10,3,'ice-cream') USING TIMESTAMP 1458134077121;

1	INSERT INTO invoices (invoice_id,amount,tax,description) VALUES ('333',10,3,'ice-cream') USING TIMESTAMP 1458134077121;

The timestamp will be set for ALL cells in this row (well not the primary key, cause it does not have a timestamp, but the others).

The timestamp is given as millisecondsÂ since EPOC, so lots of digitsÂ :-).

A prepared statement would then look like this (Scala code)

val cql = "INSERT INTO invoices (invoice_id,amount,tax,description) VALUES (?,?,?,?) USING TIMESTAMP ?;"

val stmt = session.prepare( cql )

val bs = stmt.bind()

bs.setString("invoice_id", "333" )

bs.setLong("amount", 10L )

bs.setLong("tax", 3L )

bs.setString("description","ice-cream")

bs.setLong("[timestamp]", 1458134077121L )

val result = Â session.execute( bs )

val cql = "INSERT INTO invoices (invoice_id,amount,tax,description) VALUES (?,?,?,?) USING TIMESTAMP ?;"

val stmt = session.prepare( cql )

val bs = stmt.bind()

bs.setString("invoice_id", "333" )

bs.setLong("amount", 10L )

bs.setLong("tax", 3L )

bs.setString("description","ice-cream")

bs.setLong("[timestamp]", 1458134077121L )

val result = Â session.execute( bs )

TTL and TIMESTAMP can both be set like this, i.e. with [ttl] and [timestamp]

-Tobias

DTrace;ing the JVM, useful tips

October 5, 2013debugging, DTrace, JAVA, JVMtobias

I am using DTrace from time to time and it is really nice, you can do a lot with it.

This page is mostly a reminder to myself cause there are tons of pages out there if you google it, but I figured that why not share the knowledge 🙂

List all Probes available in a process

# <strong>dtrace -ln 'pid$target:::entry' -p 809</strong>
   ID   PROVIDER            MODULE                          FUNCTION NAME
62650     pid809              bash                             __fsr entry
62651     pid809              bash                              main entry
62652     pid809              bash                        exit_shell entry
62653     pid809              bash                           sh_exit entry
62654     pid809              bash               shell_is_restricted entry
[...6778 lines truncated...]

# <strong>dtrace -ln 'pid$target:::entry' -p 809</strong>

ID PROVIDER MODULE FUNCTION NAME

62650 pid809 bash __fsr entry

62651 pid809 bash main entry

62652 pid809 bash exit_shell entry

62653 pid809 bash sh_exit entry

62654 pid809 bash shell_is_restricted entry

[...6778 lines truncated...]

Â List all probes that has to do with the JAVA JVM Hotspot

dtrace -l | grep hotspot

Figure out WHO initiated the Garbage Collection (GC)

dtrace -n ‘hotspot$target:::gc-begin { jstack(); }’ -p 25736

dtrace: description 'hotspot$target:::gc-begin ' matched 4 probes
CPU ID FUNCTION:NAME 
0 54737 __1cRVM_GenCollectFullEdoit6M_v_:gc-begin 
libjvm.so`__1cRVM_GenCollectFullEdoit6M_v_+0x24 
libjvm.so`__1cMVM_OperationIevaluate6M_v_+0x79 
libjvm.so`__1cIVMThreadDrun6M_v_+0x548 
libjvm.so`java_start+0x9d2 
libc.so.1`_thr_setup+0x5b 
libc.so.1`_lwp_start

dtrace: description 'hotspot$target:::gc-begin ' matched 4 probes

CPU ID FUNCTION:NAME

0 54737 __1cRVM_GenCollectFullEdoit6M_v_:gc-begin

libjvm.so`__1cRVM_GenCollectFullEdoit6M_v_+0x24

libjvm.so`__1cMVM_OperationIevaluate6M_v_+0x79

libjvm.so`__1cIVMThreadDrun6M_v_+0x548

libjvm.so`java_start+0x9d2

libc.so.1`_thr_setup+0x5b

libc.so.1`_lwp_start

JVM Probes

http://docs.oracle.com/javase/6/docs/technotes/guides/vm/dtrace.html

Figure out what objects are being allocated using DTrace

http://prefetch.net/blog/index.php/2007/10/31/using-the-dtrace-hotspot-provider-to-observe-java-object-allocations/

JVM: Unable to open door

$ <b>jinfo -flag +ExtendedDTraceProbes `pgrep java`</b>
 590: Unable to open door: target process not responding or HotSpot VM not loaded

1 2	$ <b>jinfo -flag +ExtendedDTraceProbes `pgrep java`</b> 590: Unable to open door: target process not responding or HotSpot VM not loaded

The jinfo command needs to be run by the user the JVM runs as.

tsoft.se

Tobias – With a Passion For Software Development

Category Archives: JAVA

Print stacktraces for all threads on shutdown

UDF/User Defined Functions in Cassandra 3.x

Cassandra set the writetime explicitly with a PreparedStatement

DTrace;ing the JVM, useful tips

Â List all probes that has to do with the JAVA JVM Hotspot

Figure out WHO initiated the Garbage Collection (GC)

JVM Probes

Figure out what objects are being allocated using DTrace

JVM: Unable to open door