airbnb 开源reAir 工具 用法及源码解析（一）

reAir 有批量复制与增量复制功能 今天我们先来看看批量复制功能

批量复制使用方式：

cd reair
./gradlew shadowjar -p main -x test
# 如果是本地table-list 一样要加file:/// ; 如果直接写  --table-list ~/reair/local_table_list ,此文件必须在hdfs上！
hadoop jar main/build/libs/airbnb-reair-main-1.0.0-all.jar com.airbnb.reair.batch.hive.MetastoreReplicationJob --config-files my_config_file.xml --table-list file:///reair/local_table_list

1.table_list 内容,用户要复制的库名.表名

db_name1.table_name1
db_name1.table_name2
db_name2.table_name3
...

2. my_config_file.xml 配置

<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>

<configuration>
  <property>
    <name>airbnb.reair.clusters.src.name</name>
    <value>ns8</value>
    <comment>
      Name of the source cluster. It can be an arbitrary string and is used in
      logs, tags, etc.
    </comment>
  </property>

  <property>
    <name>airbnb.reair.clusters.src.metastore.url</name>
    <value>thrift://192.168.200.140:9083</value>
    <comment>Source metastore Thrift URL.</comment>
  </property>

  <property>
    <name>airbnb.reair.clusters.src.hdfs.root</name>
    <value>hdfs://ns8/</value>
    <comment>Source cluster HDFS root. Note trailing slash.</comment>
  </property>

  <property>
    <name>airbnb.reair.clusters.src.hdfs.tmp</name>
    <value>hdfs://ns8/tmp</value>
    <comment>
      Directory for temporary files on the source cluster.
    </comment>
  </property>

  <property>
    <name>airbnb.reair.clusters.dest.name</name>
    <value>ns1</value>
    <comment>
      Name of the destination cluster. It can be an arbitrary string and is used in
      logs, tags, etc.
    </comment>
  </property>

  <property>
    <name>airbnb.reair.clusters.dest.metastore.url</name>
    <value>thrift://dev04:9083</value>
    <comment>Destination metastore Thrift URL.</comment>
  </property>

  <property>
    <name>airbnb.reair.clusters.dest.hdfs.root</name>
    <value>hdfs://ns1/</value>
    <comment>Destination cluster HDFS root. Note trailing slash.</comment>
  </property>

  <property>
    <name>airbnb.reair.clusters.dest.hdfs.tmp</name>
    <value>hdfs://ns1/tmp</value>
    <comment>
      Directory for temporary files on the source cluster. Table / partition
      data is copied to this location before it is moved to the final location,
      so it should be on the same filesystem as the final location.
    </comment>
  </property>

  <property>
    <name>airbnb.reair.clusters.batch.output.dir</name>
    <value>/tmp/replica</value>
    <comment>
      This configuration must be provided. It gives location to store each stage
      MR job output.
    </comment>
  </property>

  <property>
    <name>airbnb.reair.clusters.batch.metastore.blacklist</name>
    <value>testdb:test.*,tmp_.*:.*</value>
    <comment>
      Comma separated regex blacklist. dbname_regex:tablename_regex,...
    </comment>
  </property>

  <property>
    <name>airbnb.reair.batch.metastore.parallelism</name>
    <value>5</value>
    <comment>
      The parallelism to use for jobs requiring metastore calls. This translates to the number of
      mappers or reducers in the relevant jobs.
    </comment>
  </property>

  <property>
    <name>airbnb.reair.batch.copy.parallelism</name>
    <value>5</value>
    <comment>
      The parallelism to use for jobs that copy files. This translates to the number of reducers
      in the relevant jobs.
    </comment>
  </property>

  <property>
    <name>airbnb.reair.batch.overwrite.newer</name>
    <value>true</value>
    <comment>
      Whether the batch job will overwrite newer tables/partitions on the destination. Default is true.
    </comment>
  </property>
 
  <property>
    <name>mapreduce.map.speculative</name>
    <value>false</value>
    <comment>
      Speculative execution is currently not supported for batch replication.
    </comment>
  </property>

  <property>
    <name>mapreduce.reduce.speculative</name>
    <value>false</value>
    <comment>
      Speculative execution is currently not supported for batch replication.
    </comment>
  </property>

</configuration>

---

reAir批量复制步骤,共三个Stage

Stage 1

Mapper:
  1. 读取用户配置.xml文件配置(setup方法)
  2. 读取用户配置的table-list内容
    1). 过滤与黑名单匹配表名
    2). 生成TaskEstimate对象，通过各种策略封装了TaskEstimate.TaskType.xxx 的操作
    3). 如果src 是分区表，通过desc metastore thrift 执行 create/alter/noop 相应表
    4). 如果是分区表，会增加Check_Partition 任务（为每个分区创建任务，如dt=20180801等）
    5). 返回List<String> result，由 	 分割
        result结构：TaskType isUpdateMeta isUpdateData srcPath destPath db_name table_name partition_name
        TaskEstimate对象：  TaskType isUpdateMeta isUpdateData srcPath destPath
        HiveObjectSpec对象：db_name table_name partition_name
    6). map 输出结果：<key:result.hashCode(), new Text(result)>
   
  
对mapper 2-3)的补充说明：
    1). COPY_UNPARTITION_TABLE
    2). NO_OP
    3). COPY_PARTITION_TABLE
        1)). CREATE(如果dest没有对应表); ALTER(如果dest存在相应表(ExistingTable), ExistingTable与我们期待的根据srcTable生成的expectTable不同); NO_OP(默认不操作)
        2)). CHECK_PARTITION(生成分区表所有分区，如dt=20180101,dt=20180102等等)
Reduce:
    1. 反序列化map的vaule值，Pair<TaskEstimate, HiveObjectSpec>
    2. 如果taskType == CHKER_PARTITION，重新对spec做任务类型校验(重复map端检验逻辑)
    3. 输出的result与map的value相同
       <new Text(result), Expection.toString>

Stage 2

Mapper:
    1. 反序列化stage1的result，如果estimate.TaskType == COPY_PARTITION_TABLE OR COPY_UNPARTITION_TABLE 并且需要更新 data 就走updateDir()方法，否则NO_OP
    2. updateDir(): 
        1). 清理destPath，并重新创建
        2). 以srcPath递归所有非隐藏文件
    3. 输出：<key:(srcFile.size + fileModificationTime).hashCode(), value:(srcFileName 	 destPath 	 srcFileSize)>

Reduce:
    1. 反序列化value
    2. 进行校验copy(重试三次)
        1). 成功日志： COPIED srcPathFileName DestPath srcFileSize "" currentSystemTime
        2). 失败(或未通过校验)日志：SKIPPED srcPathFileName DestPath srcFileSize Expection.toString currentSystemTime
        

Stage 3

只有mapper任务
Mapper:
    1. Input为Stage1的输出(<new Text(result), Expection.toString>)
    2. 判断Stage1的结果反序列化得到Estimate.TaskType，进行src/dest元数据的校验，并根据策略进行相应的 CREATE/ALTER/NOOP 操作

官方图参考：