Metrics statistics of Seata Client SDK

## Metrics statistics of Seata Client SDK

### Description:
- metrics statistics help users effectively monitor the execution process and identify possible problems.

### Tasks:
- The main monitoring indicators on the client SDK side include: Global begin / commit / rollback, branch registry / flush undo / report / commit / rollback and other status statistics.

- In addition, the calls to hooks such as undolog and fence should also be counted by metrics.

### Difficulty
- Basic

### Mentor
- Yang Liu (@lvekee , [734843455@qq.com](mailto:734843455@qq.com)), ASoC Mentor, Top contributor of Seata.

### Programming language:
- Java

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## Seata client SDK侧的metrics统计

### 描述：
- metrics统计有助于帮助使用对Seata的执行过程进行有效的监控，帮助发现可能存在的问题。

### 任务：
- 客户端SDK侧的主要监控指标包括：Global begin/commit/rollback， Branch registry/flush undolog/report/commit/rollback等状态统计。
- 另外，对undolog，fence等hook的调用也要做metrics统计。

### 难度
- 基础

### 导师
- Yang Liu (@lvekee , [734843455@qq.com](mailto:734843455@qq.com)), ASoC Mentor, Top contributor of Seata.

### 编程语言：
- Java

The issue names no files, tests, or entry points. Start by locating the Seata client SDK paths for global and branch transaction operations, then inspect the undolog and fence hook calls; done means those operations and hook invocations expose the requested metrics and are covered by suitable tests.

Written by the indexing model from the issue text.