【原创】大数据基础之Azkaban（1）简介、源代码解析

Azkaban3.45

一 简介

1 官网

https://azkaban.github.io/

Azkaban was implemented at LinkedIn to solve the problem of Hadoop job dependencies. We had jobs that needed to run in order, from ETL jobs to data analytics products.

Initially a single server solution, with the increased number of Hadoop users over the years, Azkaban has evolved to be a more robust solution.

Azkaban是由LinkedIn为了解决Hadoop环境下任务依赖问题而开发的，LinkedIn团队有很多任务需要按照顺序运行，包括ETL任务以及数据分析任务；

Azkaban一开始是单server方案，现在已经演化为一个更健壮的方案；（可惜当前版本的WebServer还是单点）

Azkaban consists of 3 key components:

• Relational Database (MySQL)
• AzkabanWebServer
• AzkabanExecutorServer

Azkaban有3个核心组件：Mysql、WebServer、ExecutorServer；

2 部署

3 数据库表结构

projects：项目

project_flows：工作流定义

execution_flows：工作流实例

execution_jobs：任务实例

triggers：调度定义

ps：表中很多数据都是编码的，enc_type是编码类型（对应的枚举为EncodingType），2是gzip编码，其他为无编码，2需要调用GZIPUtils.transformBytesToObject解析得到原始字符串；

4 概念

l  Job：最小的执行单元，作为DAG的一个结点，即任务

l  Flow：由多个Job组成，并通过dependent配置Job的依赖属性，即工作流

l  Tirgger：根据指定Cron信息触发Flow，即调度

二 代码解析

1 启动过程

Web Server

AzkabanWebServer.main

         launch

                  prepareAndStartServer

                          configureRoutes

                                   TriggerManager.start

                          FlowTriggerService.start

                                   recoverIncompleteTriggerInstances

                                            SELECT %s FROM execution_dependencies WHERE trigger_instance_id in (SELECT trigger_instance_id FROM execution_dependencies WHERE dep_status = %s or dep_status = %s or (dep_status = %s and flow_exec_id = %s))

                          FlowTriggerScheduler.start

ExecutorManager

         setupExecutors

         loadRunningFlows

QueueProcessorThread.run

ExecutingManagerUpdaterThread.run

Executor Server

AzkabanExecutorServer.main

         launch

                  AzkabanExecutorServer.start

                          insertExecutorEntryIntoDB

2 工作流执行过程

Web Server两个入口：

ExecuteFlowAction.doAction

ExecutorServlet.ajaxExecuteFlow

Web Server分配任务：

ExecutorManager.submitExecutableFlow

         JdbcExecutorLoader.uploadExecutableFlow

                  INSERT INTO execution_flows (project_id, flow_id, version, status, submit_time, submit_user, update_time) values (?,?,?,?,?,?,?)

         ExecutorLoader.addActiveExecutableReference

                  INSERT INTO active_executing_flows (exec_id, update_time) values (?,?)

         queuedFlows.enqueue

QueueProcessorThread.run

         processQueuedFlows

                  ExecutorManager.selectExecutorAndDispatchFlow (get from queuedFlows)

                          selectExecutor

                          dispatch

                                   JdbcExecutorLoader.assignExecutor

                                            UPDATE execution_flows SET executor_id=? where exec_id=?

                                   ExecutorApiGateway.callWithExecutable （调用Executor Server）

Executor Server执行任务：

ExecutorServlet.doGet

         handleAjaxExecute

                  FlowRunnerManager.submitFlow

                          JdbcExecutorLoader.fetchExecutableFlow

                                 SELECT exec_id, enc_type, flow_data FROM execution_flows WHERE exec_id=?

                          FlowPreparer.setup

                          FlowRunner.run

                                   setupFlowExecution

                                   updateFlow

                                            UPDATE execution_flows SET status=?,update_time=?,start_time=?,end_time=?,enc_type=?,flow_data=? WHERE exec_id=?

                                   runFlow

                                            progressGraph

                                                     runReadyJob

                                                             runExecutableNode

                                                                      JobRunner.run

                                                                               uploadExecutableNode

                                                                                        INSERT INTO execution_jobs (exec_id, project_id, version, flow_id, job_id, start_time, end_time, status, input_params, attempt) VALUES (?,?,?,?,?,?,?,?,?,?)

                                                                               prepareJob

                                                                               runJob

                                                                                        Job.run (ProcessJob, JavaJob)

Web Server轮询流程状态：

ExecutingManagerUpdaterThread.run

         getFlowToExecutorMap

         ExecutorApiGateway.callWithExecutionId

         updateExecution

3 调度执行过程

TriggerManager.start

         loadTriggers

                  SELECT trigger_id, trigger_source, modify_time, enc_type, data FROM triggers

         TriggerScannerThread.start

                  checkAllTriggers

                          onTriggerTrigger

                                   TriggerAction.doAction

                                            ExecuteFlowAction.doAction

PS：还有另一套完全独立的定时任务逻辑，通过azkaban.server.schedule.enable_quartz控制（默认false），以下为register job到quartz：

ProjectManagerServlet.ajaxHandleUpload

         SELECT id, name, active, modified_time, create_time, version, last_modified_by, description, enc_type, settings_blob FROM projects WHERE name=? AND active=true

         ProjectManager.loadAllProjectFlows

                  SELECT project_id, version, flow_id, modified_time, encoding_type, json FROM project_flows WHERE project_id=? AND version=?

         FlowTriggerScheduler.scheduleAll

                  SELECT MAX(flow_version) FROM project_flow_files WHERE project_id=? AND project_version=? AND flow_name=?

                  SELECT flow_file FROM project_flow_files WHERE project_id=? AND project_version=? AND flow_name=? AND flow_version=?

                  registerJob

以下为quartz job执行：

FlowTriggerQuartzJob.execute

         FlowTriggerService.startTrigger

                  TriggerInstanceProcessor.processSucceed

                          TriggerInstanceProcessor.executeFlowAndUpdateExecID

                                   ExecutorManager.submitExecutableFlow

4 任务执行过程

Job是任务的核心接口，所有具体任务都是该接口的子类：

Job

         AbstractJob

                  AbstractProcessJob

                          ProcessJob （Shell任务）

                                   JavaProcessJob （Java任务）

                                            JavaJob