# monitor

[`monitor`在线教程](https://arthas.aliyun.com/doc/arthas-tutorials.html?language=cn&id=command-monitor)

::: tip
方法执行监控
:::

对匹配 `class-pattern`／`method-pattern`／`condition-express`的类、方法的调用进行监控。

`monitor` 命令是一个非实时返回命令.

实时返回命令是输入之后立即返回，而非实时返回的命令，则是不断的等待目标 Java 进程返回信息，直到用户输入 `Ctrl+C` 为止。

服务端是以任务的形式在后台跑任务，植入的代码随着任务的中止而不会被执行，所以任务关闭后，不会对原有性能产生太大影响，而且原则上，任何 Arthas 命令不会引起原有业务逻辑的改变。

## 监控的维度说明

|    监控项 | 说明                       |
| --------: | :------------------------- |
| timestamp | 时间戳                     |
|     class | Java 类                    |
|    method | 方法（构造方法、普通方法） |
|     total | 调用次数                   |
|   success | 成功次数                   |
|      fail | 失败次数                   |
|        rt | 平均 RT                    |
| fail-rate | 失败率                     |

## 参数说明

方法拥有一个命名参数 `[c:]`，意思是统计周期（cycle of output），拥有一个整型的参数值

|            参数名称 | 参数说明                                                           |
| ------------------: | :----------------------------------------------------------------- |
|     _class-pattern_ | 类名表达式匹配                                                     |
|    _method-pattern_ | 方法名表达式匹配                                                   |
| _condition-express_ | 条件表达式                                                         |
|                 [E] | 开启正则表达式匹配，默认为通配符匹配                               |
|              `[c:]` | 统计周期，默认值为 120 秒                                          |
|                 [b] | 在**方法调用之前**计算 condition-express                           |
|         `[m <arg>]` | 指定 Class 最大匹配数量，默认值为 50。长格式为`[maxMatch <arg>]`。 |

## 使用参考

```bash
$ monitor -c 5 demo.MathGame primeFactors
Press Ctrl+C to abort.
Affect(class-cnt:1 , method-cnt:1) cost in 94 ms.
 timestamp            class          method        total  success  fail  avg-rt(ms)  fail-rate
-----------------------------------------------------------------------------------------------
 2018-12-03 19:06:38  demo.MathGame  primeFactors  5      1        4     1.15        80.00%

 timestamp            class          method        total  success  fail  avg-rt(ms)  fail-rate
-----------------------------------------------------------------------------------------------
 2018-12-03 19:06:43  demo.MathGame  primeFactors  5      3        2     42.29       40.00%

 timestamp            class          method        total  success  fail  avg-rt(ms)  fail-rate
-----------------------------------------------------------------------------------------------
 2018-12-03 19:06:48  demo.MathGame  primeFactors  5      3        2     67.92       40.00%

 timestamp            class          method        total  success  fail  avg-rt(ms)  fail-rate
-----------------------------------------------------------------------------------------------
 2018-12-03 19:06:53  demo.MathGame  primeFactors  5      2        3     0.25        60.00%

 timestamp            class          method        total  success  fail  avg-rt(ms)  fail-rate
-----------------------------------------------------------------------------------------------
 2018-12-03 19:06:58  demo.MathGame  primeFactors  1      1        0     0.45        0.00%

 timestamp            class          method        total  success  fail  avg-rt(ms)  fail-rate
-----------------------------------------------------------------------------------------------
 2018-12-03 19:07:03  demo.MathGame  primeFactors  2      2        0     3182.72     0.00%
```

### 指定 Class 最大匹配数量

```bash
$ monitor -c 1 -m 1 demo.MathGame primeFactors
Press Q or Ctrl+C to abort.
Affect(class count:1 , method count:1) cost in 384 ms, listenerId: 6.
 timestamp            class          method        total  success  fail  avg-rt(ms)  fail-rate
-----------------------------------------------------------------------------------------------
 2022-12-25 21:12:58  demo.MathGame  primeFactors  1      1        0     0.18        0.00%

 timestamp            class          method        total  success  fail  avg-rt(ms)  fail-rate
-----------------------------------------------------------------------------------------------
 2022-12-25 21:12:59  demo.MathGame  primeFactors  0      0        0     0.00       0.00%
```

### 计算条件表达式过滤统计结果(方法执行完毕之后)

```bash
monitor -c 5 demo.MathGame primeFactors "params[0] <= 2"
Press Q or Ctrl+C to abort.
Affect(class count: 1 , method count: 1) cost in 19 ms, listenerId: 5
 timestamp            class          method         total  success  fail  avg-rt(ms)  fail-rate
-----------------------------------------------------------------------------------------------
 2020-09-02 09:42:36  demo.MathGame  primeFactors    5       3       2      0.09       40.00%

 timestamp            class          method         total  success  fail  avg-rt(ms)  fail-rate
----------------------------------------------------------------------------------------------
 2020-09-02 09:42:41  demo.MathGame  primeFactors    5       2       3      0.11       60.00%

 timestamp            class          method         total  success  fail  avg-rt(ms)  fail-rate
----------------------------------------------------------------------------------------------
 2020-09-02 09:42:46  demo.MathGame  primeFactors    5       1       4      0.06       80.00%

 timestamp            class          method         total  success  fail  avg-rt(ms)  fail-rate
----------------------------------------------------------------------------------------------
 2020-09-02 09:42:51  demo.MathGame  primeFactors    5       1       4      0.12       80.00%

 timestamp            class          method         total  success  fail  avg-rt(ms)  fail-rate
----------------------------------------------------------------------------------------------
 2020-09-02 09:42:56  demo.MathGame  primeFactors    5       3       2      0.15       40.00%
```

### 计算条件表达式过滤统计结果(方法执行完毕之前)

```bash
monitor -b -c 5 com.test.testes.MathGame primeFactors "params[0] <= 2"
Press Q or Ctrl+C to abort.
Affect(class count: 1 , method count: 1) cost in 21 ms, listenerId: 4
 timestamp            class          method         total  success  fail  avg-rt(ms)  fail-rate
----------------------------------------------------------------------------------------------
 2020-09-02 09:41:57  demo.MathGame  primeFactors    1       0        1      0.10      100.00%

 timestamp            class          method         total  success  fail  avg-rt(ms)  fail-rate
----------------------------------------------------------------------------------------------
 2020-09-02 09:42:02  demo.MathGame  primeFactors    3       0        3      0.06      100.00%

 timestamp            class          method         total  success  fail  avg-rt(ms)  fail-rate
----------------------------------------------------------------------------------------------
 2020-09-02 09:42:07  demo.MathGame  primeFactors    2       0        2      0.06      100.00%

 timestamp            class          method         total  success  fail  avg-rt(ms)  fail-rate
----------------------------------------------------------------------------------------------
 2020-09-02 09:42:12  demo.MathGame  primeFactors    1       0        1      0.05      100.00%

 timestamp            class          method         total  success  fail  avg-rt(ms)  fail-rate
----------------------------------------------------------------------------------------------
 2020-09-02 09:42:17  demo.MathGame  primeFactors    2       0        2      0.10      100.00%
```