Merge pull request #19 from leilinen/master

checkpoints 翻译

docs/1.7/115.md

 
 
-# Checkpoints
+# 检查点
+
+## 概览
 
 ## Overview
 
+检查点通过恢复任务状态和流的位置使flink达到容错的特性，从而为flink任务提供与无故障执行相同的语句。
+
 Checkpoints make state in Flink fault tolerant by allowing state and the corresponding stream positions to be recovered, thereby giving the application the same semantics as a failure-free execution.
 
+查看[检查点](https://ci.apache.org/projects/flink/flink-docs-release-1.7/dev/stream/state/checkpointing.html)如何在你的flink任务开启和设置checkpoints机制。
+
 See [Checkpointing](//ci.apache.org/projects/flink/flink-docs-release-1.7/dev/stream/state/checkpointing.html) for how to enable and configure checkpoints for your program.
 
+## 检查点保留机制
+
 ## Retained Checkpoints
 
+默认情况下，检查点不会保留，只有在任务失败的情况下才会使用。当程序被取消，它们也会被删除。但是你可以配置要保留的检查点。根据配置，当任务失败或取消时，检查点不会自动被清除，这样你可以通过检查点来恢复失败的任务。
+
 Checkpoints are by default not retained and are only used to resume a job from failures. They are deleted when a program is cancelled. You can, however, configure periodic checkpoints to be retained. Depending on the configuration these _retained_ checkpoints are _not_ automatically cleaned up when the job fails or is canceled. This way, you will have a checkpoint around to resume from if your job fails.
 
 
@@ -19,7 +29,11 @@ CheckpointConfig config = env.getCheckpointConfig();
 config.enableExternalizedCheckpoints(ExternalizedCheckpointCleanup.RETAIN_ON_CANCELLATION);
 ```
 
+`ExternalizedCheckpointCleanup`： 模式指定了当你取消任务的时候会发生什么。
+
+*   **`ExternalizedCheckpointCleanup.RETAIN_ON_CANCELLATION`**：当任务被取消保留检查点。注意在这种情况下，任务被取消后你必须手动去清除检查点状态。
 
+*   **`ExternalizedCheckpointCleanup.DELETE_ON_CANCELLATION`**: 当任务被取消删除检查点。只有当任务失败检查点的状态才会有效。 
 
 The `ExternalizedCheckpointCleanup` mode configures what happens with checkpoints when you cancel the job:
 
@@ -27,10 +41,20 @@ The `ExternalizedCheckpointCleanup` mode configures what happens with checkpoint
 
 *   **`ExternalizedCheckpointCleanup.DELETE_ON_CANCELLATION`**: Delete the checkpoint when the job is cancelled. The checkpoint state will only be available if the job fails.
 
+### 目录结构
+
 ### Directory Structure
 
+与[保存点](savepoints.html)相同，检查点文件包含一个元数据文件以及一些其他数据文件，具体取决于状态后端。元数据文件和数据文件保存的目录由`state.checkpoints.dir` 参数配置，也可以再每个任务的代码中单独指定。
+
 Similarly to [savepoints](savepoints.html), a checkpoint consists of a meta data file and, depending on the state backend, some additional data files. The meta data file and data files are stored in the directory that is configured via `state.checkpoints.dir` in the configuration files, and also can be specified for per job in the code.
 
+#### 通过配置文件设置全局路径 
+
+```
+state.checkpoints.dir: hdfs:///checkpoints/
+```
+
 #### Configure globally via configuration files
 
 
@@ -39,7 +63,11 @@ Similarly to [savepoints](savepoints.html), a checkpoint consists of a meta data
 state.checkpoints.dir: hdfs:///checkpoints/
 ```
 
+#### 在构造状态后端时为每一个任务配置检查点路径
 
+```
+env.setStateBackend(new RocksDBStateBackend("hdfs:///checkpoints-data/");
+```
 
 #### Configure for per job when constructing the state backend
 
@@ -50,16 +78,31 @@ env.setStateBackend(new RocksDBStateBackend("hdfs:///checkpoints-data/");
 ```
 
 
+### 与保存点的差异
 
 ### Difference to Savepoints
 
+检查点与保存点有一些不同，主要在
+
+*   使用状态后端特定的数据格式，可能是增量的。
+
+*   不支持flink的特定功能，例如重新缩放。
+
 Checkpoints have a few differences from [savepoints](savepoints.html). They
 
 *   use a state backend specific (low-level) data format, may be incremental.
 *   do not support Flink specific features like rescaling.
 
+### 通过保留的检查点恢复任务
+
 ### Resuming from a retained checkpoint
 
+通过使用检查点的元数据文件，可以从检查点恢复作业，就像从保存点恢复一样（请参阅[保存点恢复指南](../cli.html#restore-a-savepoint)）。注意如果元数据文件不是自包含的，作业管理器需要访问它指向的数据文件（查看上面的[目录结构](#目录结构)）。
+
+```
+$ bin/flink run -s :checkpointMetaDataPath [:runArgs]
+```
+
 A job may be resumed from a checkpoint just as from a savepoint by using the checkpoint’s meta data file instead (see the [savepoint restore guide](../cli.html#restore-a-savepoint)). Note that if the meta data file is not self-contained, the jobmanager needs to have access to the data files it refers to (see [Directory Structure](#directory-structure) above).