tt¶
Check the parameters, return values and exceptions of the methods at different times.
watch is a powerful command but due to its feasibility and complexity, it’s quite hard to locate the issue effectively.
In such difficulties, tt comes into play.
With the help of tt (TimeTunnel), you can check the contexts of the methods at different times in execution history.
Usage¶
Let’s record the whole calling contexts:
$ tt -t -n 3 *Test print
Press Ctrl+D or Ctrl+X to abort.
Affect(class-cnt:1 , method-cnt:1) cost in 115 ms.
+----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+
| INDEX | TIMESTAMP | COST(ms) | IS-RET | IS-EXP | OBJECT | CLASS | METHOD |
+----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+
| 1007 | 2015-07-26 12:23:21 | 138 | true | false | 0x42cc13a0 | GaOgnlUtilsTest | print |
+----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+
| 1008 | 2015-07-26 12:23:22 | 143 | true | false | 0x42cc13a0 | GaOgnlUtilsTest | print |
+----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+
| 1009 | 2015-07-26 12:23:23 | 130 | true | false | 0x42cc13a0 | GaOgnlUtilsTest | print |
+----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+
$
F.Y.I¶
-trecord the calling context of the method
*Test.print-n 3limit the number of the records (avoid overflow for too many records; with
-noption, Arthas can automatically stop recording once the records reach the specified limit)
Property¶
| Name | Specification |
|---|---|
| INDEX | the index for each call based on time |
| TIMESTAMP | time to invoke the method |
| COST(ms) | time cost of the method call |
| IS-RET | whether method exits with normal return |
| IS-EXP | whether method failed with exceptions |
| OBJECT | hashCode() of the object invoking the method |
| CLASS | class name of the object invoking the method |
| METHOD | method being invoked |
Condition expression¶
Tips:
tt -t *Test print params[0].length==1with different amounts of parameters;tt -t *Test print 'params[1] instanceof Integer'with different types of parameters;tt -t *Test print params[0].mobile=="13989838402"with specified parameter.
Advanced:
Searching for records¶
All the recorded¶
$ tt -l
+----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+
| INDEX | TIMESTAMP | COST(ms) | IS-RET | IS-EXP | OBJECT | CLASS | METHOD |
+----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+
| 1000 | 2015-07-26 01:16:27 | 130 | true | false | 0x42cc13a0 | GaOgnlUtilsTest | print |
+----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+
| 1001 | 2015-07-26 01:16:27 | 0 | false | true | 0x42cc13a0 | GaOgnlUtilsTest | printAddress |
+----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+
| 1002 | 2015-07-26 01:16:28 | 119 | true | false | 0x42cc13a0 | GaOgnlUtilsTest | print |
+----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+
| 1003 | 2015-07-26 01:16:28 | 0 | false | true | 0x42cc13a0 | GaOgnlUtilsTest | printAddress |
+----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+
| 1004 | 2015-07-26 12:21:56 | 130 | true | false | 0x42cc13a0 | GaOgnlUtilsTest | print |
+----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+
| 1005 | 2015-07-26 12:21:57 | 138 | true | false | 0x42cc13a0 | GaOgnlUtilsTest | print |
+----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+
| 1006 | 2015-07-26 12:21:58 | 130 | true | false | 0x42cc13a0 | GaOgnlUtilsTest | print |
+----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+
Affect(row-cnt:7) cost in 2 ms.
$
A specified method¶
$ tt -s method.name=="printAddress"
+----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+
| INDEX | TIMESTAMP | COST(ms) | IS-RET | IS-EXP | OBJECT | CLASS | METHOD |
+----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+
| 1001 | 2015-07-26 01:16:27 | 0 | false | true | 0x42cc13a0 | GaOgnlUtilsTest | printAddress |
+----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+
| 1003 | 2015-07-26 01:16:28 | 0 | false | true | 0x42cc13a0 | GaOgnlUtilsTest | printAddress |
+----------+----------------------+------------+----------+----------+-----------------+--------------------------------+--------------------------------+
Affect(row-cnt:2) cost in 55 ms.
$
Advanced:
Check context of the call¶
Using tt -i <index> to check a specific calling details.
$
$ tt -i 1003
+-----------------+------------------------------------------------------------------------------------------------------+
| INDEX | 1003 |
+-----------------+------------------------------------------------------------------------------------------------------+
| GMT-CREATE | 2015-07-26 01:16:28 |
+-----------------+------------------------------------------------------------------------------------------------------+
| COST(ms) | 0 |
+-----------------+------------------------------------------------------------------------------------------------------+
| OBJECT | 0x42cc13a0 |
+-----------------+------------------------------------------------------------------------------------------------------+
| CLASS | GaOgnlUtilsTest |
+-----------------+------------------------------------------------------------------------------------------------------+
| METHOD | printAddress |
+-----------------+------------------------------------------------------------------------------------------------------+
| IS-RETURN | false |
+-----------------+------------------------------------------------------------------------------------------------------+
| IS-EXCEPTION | true |
+-----------------+------------------------------------------------------------------------------------------------------+
| PARAMETERS[0] | Address@53448f87 |
+-----------------+------------------------------------------------------------------------------------------------------+
| THROW-EXCEPTION | java.lang.RuntimeException: test |
| | at GaOgnlUtilsTest.printAddress(Unknown Source) |
| | at GaOgnlUtilsTest.<init>(Unknown Source) |
| | at GaOgnlUtilsTest.main(Unknown Source) |
+-----------------+------------------------------------------------------------------------------------------------------+
Affect(row-cnt:1) cost in 1 ms.
$
Re-produce¶
Since Arthas stores the context of the call, you can even replay the method calling afterwards with extra option -p to re-produce the issue for advanced troubleshooting.
$ tt -i 1003 -p
+-----------------+---------------------------------------------------------------------------------------------------------+
| RE-INDEX | 1003 |
+-----------------+---------------------------------------------------------------------------------------------------------+
| GMT-REPLAY | 2015-07-26 17:29:51 |
+-----------------+---------------------------------------------------------------------------------------------------------+
| OBJECT | 0x42cc13a0 |
+-----------------+---------------------------------------------------------------------------------------------------------+
| CLASS | GaOgnlUtilsTest |
+-----------------+---------------------------------------------------------------------------------------------------------+
| METHOD | printAddress |
+-----------------+---------------------------------------------------------------------------------------------------------+
| PARAMETERS[0] | Address@53448f87 |
+-----------------+---------------------------------------------------------------------------------------------------------+
| IS-RETURN | false |
+-----------------+---------------------------------------------------------------------------------------------------------+
| IS-EXCEPTION | true |
+-----------------+---------------------------------------------------------------------------------------------------------+
| THROW-EXCEPTION | java.lang.RuntimeException: test |
| | at GaOgnlUtilsTest.printAddress(GaOgnlUtilsTest.java:78) |
| | at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) |
| | at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) |
| | at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) |
| | at java.lang.reflect.Method.invoke(Method.java:483) |
| | at com.github.ompc.Arthas.util.GaMethod.invoke(GaMethod.java:81) |
| | at com.github.ompc.Arthas.command.TimeTunnelCommand$6.action(TimeTunnelCommand.java:592) |
| | at com.github.ompc.Arthas.server.DefaultCommandHandler.execute(DefaultCommandHandler.java:175) |
| | at com.github.ompc.Arthas.server.DefaultCommandHandler.executeCommand(DefaultCommandHandler.java:83) |
| | at com.github.ompc.Arthas.server.GaServer$4.run(GaServer.java:329) |
| | at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) |
| | at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) |
| | at java.lang.Thread.run(Thread.java:745) |
+-----------------+---------------------------------------------------------------------------------------------------------+
replay time fragment[1003] success.
Affect(row-cnt:1) cost in 3 ms.
$
F.Y.I
- the calling stack is little different using Arthas now unlike the original;
- Loss of the thread local variables will be a undeniable fact since there is no way for Arthas to record the thread local info (If you find one, please share with us in issues tracker).
- Potential modifications of objects can happen since only a reference will be recorded while later operations might modify objects without Arthas’s watch.