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166 lines
6.7 KiB
Markdown
166 lines
6.7 KiB
Markdown
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Check the `parameters`, `return values` and `exceptions` of the methods at different times.
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`watch` is a powerful command but due to its feasibility and complexity, it's quite hard to locate the issue effectively.
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In such difficulties, `tt` comes into play.
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With the help of `tt` (*TimeTunnel*), you can check the contexts of the methods at different times in execution history.
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### Usage
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#### Record method calls
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`tt -t demo.MathGame primeFactors`{{execute T2}}
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Press `Q`{{execute T2}} or `Ctrl+C` to abort
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```bash
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$ tt -t demo.MathGame primeFactors
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Press Ctrl+C to abort.
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Affect(class-cnt:1 , method-cnt:1) cost in 66 ms.
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INDEX TIMESTAMP COST(ms) IS-RET IS-EXP OBJECT CLASS METHOD
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-------------------------------------------------------------------------------------------------------------------------------------
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1000 2018-12-04 11:15:38 1.096236 false true 0x4b67cf4d MathGame primeFactors
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1001 2018-12-04 11:15:39 0.191848 false true 0x4b67cf4d MathGame primeFactors
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1002 2018-12-04 11:15:40 0.069523 false true 0x4b67cf4d MathGame primeFactors
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1003 2018-12-04 11:15:41 0.186073 false true 0x4b67cf4d MathGame primeFactors
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1004 2018-12-04 11:15:42 17.76437 true false 0x4b67cf4d MathGame primeFactors
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```
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* `-t`
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record the calling context of the method `demo.MathGame primeFactors`
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* `-n 3`
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limit the number of the records (avoid overflow for too many records; with `-n` option, Arthas can automatically stop recording once the records reach the specified limit)
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* Property
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|Name|Specification|
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|---|---|
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|INDEX|the index for each call based on time|
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|TIMESTAMP|time to invoke the method|
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|COST(ms)|time cost of the method call|
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|IS-RET|whether method exits with normal return|
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|IS-EXP|whether method failed with exceptions|
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|OBJECT|`hashCode()` of the object invoking the method|
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|CLASS|class name of the object invoking the method|
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|METHOD|method being invoked|
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* Condition expression
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Tips:
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1. `tt -t *Test print params.length==1` with different amounts of parameters;
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2. `tt -t *Test print 'params[1] instanceof Integer'` with different types of parameters;
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3. `tt -t *Test print params[0].mobile=="13989838402"` with specified parameter.
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Advanced:
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* [Critical fields in expression](https://arthas.aliyun.com/doc/en/advice-class.html)
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* [Special usage](https://github.com/alibaba/arthas/issues/71)
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* [OGNL official guide](https://commons.apache.org/proper/commons-ognl/language-guide.html)
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#### List all records
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`tt -l`{{execute T2}}
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```bash
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$ tt -l
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INDEX TIMESTAMP COST(ms) IS-RET IS-EXP OBJECT CLASS METHOD
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-------------------------------------------------------------------------------------------------------------------------------------
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1000 2018-12-04 11:15:38 1.096236 false true 0x4b67cf4d MathGame primeFactors
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1001 2018-12-04 11:15:39 0.191848 false true 0x4b67cf4d MathGame primeFactors
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1002 2018-12-04 11:15:40 0.069523 false true 0x4b67cf4d MathGame primeFactors
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1003 2018-12-04 11:15:41 0.186073 false true 0x4b67cf4d MathGame primeFactors
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1004 2018-12-04 11:15:42 17.76437 true false 0x4b67cf4d MathGame primeFactors
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9
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1005 2018-12-04 11:15:43 0.4776 false true 0x4b67cf4d MathGame primeFactors
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Affect(row-cnt:6) cost in 4 ms.
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```
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#### Searching for records
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`tt -s 'method.name=="primeFactors"'`{{execute T2}}
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```bash
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$ tt -s 'method.name=="primeFactors"'
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INDEX TIMESTAMP COST(ms) IS-RET IS-EXP OBJECT CLASS METHOD
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-------------------------------------------------------------------------------------------------------------------------------------
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1000 2018-12-04 11:15:38 1.096236 false true 0x4b67cf4d MathGame primeFactors
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1001 2018-12-04 11:15:39 0.191848 false true 0x4b67cf4d MathGame primeFactors
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1002 2018-12-04 11:15:40 0.069523 false true 0x4b67cf4d MathGame primeFactors
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1003 2018-12-04 11:15:41 0.186073 false true 0x4b67cf4d MathGame primeFactors
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1004 2018-12-04 11:15:42 17.76437 true false 0x4b67cf4d MathGame primeFactors
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9
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1005 2018-12-04 11:15:43 0.4776 false true 0x4b67cf4d MathGame primeFactors
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Affect(row-cnt:6) cost in 607 ms.
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```
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Advanced:
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* [Critical fields in expression](advice-class.md)
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#### Check context of the call
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`tt -i 1003`{{execute T2}}
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Using `tt -i <index>` to check a specific calling details.
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```bash
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$ tt -i 1003
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INDEX 1003
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GMT-CREATE 2018-12-04 11:15:41
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COST(ms) 0.186073
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OBJECT 0x4b67cf4d
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CLASS demo.MathGame
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METHOD primeFactors
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IS-RETURN false
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IS-EXCEPTION true
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PARAMETERS[0] @Integer[-564322413]
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THROW-EXCEPTION java.lang.IllegalArgumentException: number is: -564322413, need >= 2
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at demo.MathGame.primeFactors(MathGame.java:46)
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at demo.MathGame.run(MathGame.java:24)
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at demo.MathGame.main(MathGame.java:16)
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Affect(row-cnt:1) cost in 11 ms.
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```
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### Replay record
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Since Arthas stores the context of the call, you can even *replay* the method calling afterwards with extra option `-p` to replay the issue for advanced troubleshooting, option `--replay-times`
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define the replay execution times, option `--replay-interval` define the interval(unit in ms,with default value 1000) of replays
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`tt -i 1004 -p`{{execute T2}}
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```bash
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$ tt -i 1004 -p
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RE-INDEX 1004
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GMT-REPLAY 2018-12-04 11:26:00
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OBJECT 0x4b67cf4d
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CLASS demo.MathGame
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METHOD primeFactors
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PARAMETERS[0] @Integer[946738738]
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IS-RETURN true
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IS-EXCEPTION false
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RETURN-OBJ @ArrayList[
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@Integer[2],
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@Integer[11],
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@Integer[17],
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@Integer[2531387],
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]
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Time fragment[1004] successfully replayed.
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Affect(row-cnt:1) cost in 14 ms.
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```
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F.Y.I
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1. **Loss** of the `ThreadLocal`
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Arthas save params into an array, then invoke the method with the params again. The method execute in another thread, so the `ThreadLocal` **lost**.
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1. params may be modified
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Arthas save params into an array, they are object references. The Objects may be modified by other code.
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