Spark深入解读（十二）---- 有向无环图DAG(代码及图解)
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目录：
1、有向无环图
2、代码结构
3、代码学习步鄹及方法
4、重点代码讲解
5、代码展现
6、运行结果
1、有向无环图
在图论中，如果一个有向图无法从某个顶点出发经过若干条边回到该点，则这个图是一个有向无环图（DAG图）。
因为有向图中一个点经过两种路线到达另一个点未必形成环，因此有向无环图未必能转化成树，但任何有向树均为有向无环图。
性质：有向无环图的生成树个数等于入度非零的节点的入度积。
2、代码结构
3、代码学习步鄹及方法
1、本文中涉及到了Spark的Dag和设计模式中的命令
2、Dag学习步鄹：task --> Node --> DAG --> DAGExecutor
3、设计模式命令 http://blog.csdn.net/silentwolfyh/article/details/52839495
4、图解Dag类的学习步鄹
4、重点代码讲解
下面这段代码是核心也是最难的，如何找到父节点
//判断Node的task节点的父节点运行状态（flase ，true）
private def getPending: Option[T] = {
_pending.find { name =>
val parents = _nodes(name)
!parents.exists(name => !_success.contains(name))
}
}
1、nodes没有父节点时，!parents.exists() 为true
2、parents.exists() 为flase时，!parents.exists() 为true
5、代码展现
DAG.scala
package com.yh.dag
import java.time.{Duration, LocalDate}
import com.yh.nodeexecutor._
import org.slf4j.LoggerFactory
import scala.collection.immutable.{ListMap, ListSet}
/**
* Created by yuhui on 2016/8/25.
* task --> Node --> DAG --> DAGExecutor
*/
case class Node[T](task: T, parent: T*) {
override def toString: String = {
s"$task(${parent.mkString(",")})"
}
}
case class DAG[T](nodes: Node[T]*)
case class DAGExecutor[T](dag: DAG[T]) {
private val LOG = LoggerFactory.getLogger(this.getClass)
private val _nodes: Map[T, Seq[T]] = dag.nodes.map(node => (node.task, node.parent.filter(_ != null))).toMap
private var _pending: Set[T] = ListSet()
private var _fails = ListMap[T, String]()
private var _success = Seq[T]()
//判断Node的task节点的父节点运行状态（flase ，true）
private def getPending: Option[T] = {
_pending.find { name =>
val parents = _nodes(name)
!parents.exists(name => !_success.contains(name))
}
}
private def fail(name: T, message: String): Unit = {
_pending -= name
_fails += name -> message
for (child <- _pending.filter(child => _nodes(child).contains(name))) {
fail(child, s"依赖的任务无法执行: $name")
}
}
private def success(name: T): Unit = {
_pending -= name
_success = _success :+ name
}
def execute(func: T => Unit): Unit = {
_pending = _nodes.keySet
_fails = ListMap()
_success = Seq()
var running = true
while (running) {
val taskOpt = getPending
if (taskOpt.nonEmpty) {
val task = taskOpt.get
val startMills = System.currentTimeMillis()
LOG.info("start task {}", task)
try {
println("=============")
func(task) //执行executor方法
println("+++++++++++++")
val time = Duration.ofMillis(System.currentTimeMillis() - startMills)
LOG.info(s"end task $task time=$time")
success(task)
} catch {
case e: Throwable => fail(task, e.getMessage)
LOG.error(e.getMessage, e)
LOG.info(s"fail task $task")
}
} else {
running = false
}
}
for (name <- _success) {
LOG.info(s"success task: $name")
}
for (name <- _fails) {
LOG.info(s"fail task: ${name._1} - ${name._2}")
}
}
}
object DAG {
val allSDKDAG = new DAG[Task](
Node(UserDetailsExecutor, WebSdkparseExecutor),
Node(UserTagExecutor, WebSdkparseExecutor,WebSdkparseExecutor),
Node(WebSdkparseExecutor),
Node(UserOverviewExecutor, WebSdkparseExecutor)
)
def main(args: Array[String]): Unit = {
DAGExecutor(allSDKDAG).execute { task =>task.executor("appkey": String, LocalDate.now(), LocalDate.now())}
}
}
Task.scala
package com.yh.dag
import java.time.LocalDate
import org.apache.spark.sql.SQLContext
import org.slf4j.LoggerFactory
/**
* Created by yuhui on 2016/12/27.
*/
abstract class Task {
protected val LOG = LoggerFactory.getLogger(this.getClass)
def executor(appkey: String, startDay: LocalDate, endDay: LocalDate): Unit
def run(appkey: String, startDay: LocalDate, endDay: LocalDate): Unit = {
executor(appkey, startDay, endDay)
}
}
abstract class Executor extends Task with SQLContextAware {
override def run(appkey: String, startDay: LocalDate, endDay: LocalDate)={}
}
trait SQLContextAware {
implicit var ctx: SQLContext = _
}
UserDetailsExecutor.scala
package com.yh.nodeexecutor
import java.time.LocalDate
import com.yh.dag.Executor
object UserDetailsExecutor extends Executor{
override def executor(appkey: String, startDay: LocalDate, endDay: LocalDate): Unit = {
println("++++我的UserDetailsProcessor的执行过程++++")
}
}
UserOverviewExecutor.scala
package com.yh.nodeexecutor
import java.time.LocalDate
import com.yh.dag.Executor
/**
* Created by yuhui on 2016/12/27.
*/
object UserOverviewExecutor extends Executor{
override def executor(appkey: String, startDay: LocalDate, endDay: LocalDate): Unit = {
println("++++我的UserOverviewProcessor的执行过程++++")
}
}
UserTagExecutor.scala
package com.yh.nodeexecutor
import java.time.LocalDate
import com.yh.dag.Executor
/**
* Created by yuhui on 2016/12/27.
*/
object UserTagExecutor extends Executor{
override def executor(appkey: String, startDay: LocalDate, endDay: LocalDate): Unit = {
println("++++我的UserTagProcessor的执行过程++++")
}
}
WebSdkparseExecutor.scala
package com.yh.nodeexecutor
import java.time.LocalDate
import com.yh.dag.Executor
/**
* Created by yuhui on 2016/12/27.
*/
object WebSdkparseExecutor extends Executor{
override def executor(appkey: String, startDay: LocalDate, endDay: LocalDate): Unit = {
println("++++我的WebSdkparseProcessor的执行过程++++")
}
}
6、运行结果
=============
++++我的WebSdkparseProcessor的执行过程++++
+++++++++++++
=============
++++我的UserDetailsProcessor的执行过程++++
+++++++++++++
=============
++++我的UserTagProcessor的执行过程++++
+++++++++++++
=============
++++我的UserOverviewProcessor的执行过程++++
+++++++++++++
Process finished with exit code 0
