Play期间会发生什么！控制器实例化？

时间：2016-02-16 18:05:44

标签： scala playframework-2.4 elastic4s

我在Play框架中的控制器中遇到奇怪的行为。我使用elastic4s连接到Elasticsearch集群，并且根据建立连接的精确时间，它可以工作，也可以不工作。我最小的例子看起来像这样：

class EsController extends Controller {


  def buildClient() = ElasticClient.transport(Settings.builder
      .put("cluster.name", "es").build,
    "127.0.0.1:9300")

  val eagerClient = buildClient()
  lazy val lazyClient = buildClient()


  object ElasticConnection extends ElasticDsl {

    def eagerStats = eagerClient.execute(get cluster stats)

    def lazyStats = lazyClient.execute(get cluster stats)
  }

  // accessible via GET /eagerStats
  def eagerStats = Action.async {
    ElasticConnection.eagerStats map (s => Ok(s.toString))
  }

  // accessible via GET /lazyStats
  def lazyStats = Action.async {
    ElasticConnection.lazyStats map (s => Ok(s.toString))
  }
}

我通过sbt run启动应用。然后我可以尝试获得两个端点。 curl localhost:9000/lazyStats/工作正常，与我的ES节点对话并返回正确的统计信息。 curl localhost:9000/eagerStats/从ES传输层抛出异常（末尾的堆栈跟踪）。由于我的代码在两种情况下都是相同的（唯一的区别是val vs lazy val），我认为构造函数是以一种奇怪的方式实例化的。任何人都可以确认或否认吗？

作为旁注，我可以创建一个单独的类来处理ES连接并@Inject它（可能使它也成为@Singleton） - 这可能是首选的解决方案。我发现所描述的行为很奇怪，我很乐意看到解释。​​

elastic4s是官方ES Java驱动程序的一个小包装器，我非常有信心在这种情况下没有任何神奇的事情发生。

更新： 我在独立进程的同一台机器上运行单节点ES群集。它配置正确，甚至还有一个kopf插件启动并运行。 REST界面工作正常;传输接口也可以工作，只要我使用懒惰的初始连接。

我正在使用ES 2.2.0（客户端和服务器端），Play 2.4.6，scala 2.11.7和SBT 0.13.8。

来自急切连接的堆栈跟踪：

play.api.http.HttpErrorHandlerExceptions$$anon$1: Execution exception[[NoNodeAvailableException: None of the configured nodes are available: [{#transport#-1}{127.0.0.1}{127.0.0.1:9300}]]]
at play.api.http.HttpErrorHandlerExceptions$.throwableToUsefulException(HttpErrorHandler.scala:265) ~[play_2.11-2.4.6.jar:2.4.6]
at play.api.http.DefaultHttpErrorHandler.onServerError(HttpErrorHandler.scala:191) ~[play_2.11-2.4.6.jar:2.4.6]
at play.api.GlobalSettings$class.onError(GlobalSettings.scala:179) [play_2.11-2.4.6.jar:2.4.6]
at play.api.DefaultGlobal$.onError(GlobalSettings.scala:212) [play_2.11-2.4.6.jar:2.4.6]
at play.api.http.GlobalSettingsHttpErrorHandler.onServerError(HttpErrorHandler.scala:94) [play_2.11-2.4.6.jar:2.4.6]
at play.core.server.netty.PlayDefaultUpstreamHandler$$anonfun$9$$anonfun$apply$1.applyOrElse(PlayDefaultUpstreamHandler.scala:151) [play-netty-server_2.11-2.4.6.jar:2.4.6]
at play.core.server.netty.PlayDefaultUpstreamHandler$$anonfun$9$$anonfun$apply$1.applyOrElse(PlayDefaultUpstreamHandler.scala:148) [play-netty-server_2.11-2.4.6.jar:2.4.6]
at scala.runtime.AbstractPartialFunction.apply(AbstractPartialFunction.scala:36) [scala-library-2.11.7.jar:na]
at scala.util.Failure$$anonfun$recover$1.apply(Try.scala:216) [scala-library-2.11.7.jar:na]
at scala.util.Try$.apply(Try.scala:192) [scala-library-2.11.7.jar:na]
at scala.util.Failure.recover(Try.scala:216) [scala-library-2.11.7.jar:na]
at scala.concurrent.Future$$anonfun$recover$1.apply(Future.scala:324) [scala-library-2.11.7.jar:na]
at scala.concurrent.Future$$anonfun$recover$1.apply(Future.scala:324) [scala-library-2.11.7.jar:na]
at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:32) [scala-library-2.11.7.jar:na]
at play.api.libs.iteratee.Execution$trampoline$.executeScheduled(Execution.scala:109) [play-iteratees_2.11-2.4.6.jar:2.4.6]
at play.api.libs.iteratee.Execution$trampoline$.execute(Execution.scala:71) [play-iteratees_2.11-2.4.6.jar:2.4.6]
at scala.concurrent.impl.CallbackRunnable.executeWithValue(Promise.scala:40) [scala-library-2.11.7.jar:na]
at scala.concurrent.impl.Promise$DefaultPromise.tryComplete(Promise.scala:248) [scala-library-2.11.7.jar:na]
at scala.concurrent.Promise$class.complete(Promise.scala:55) [scala-library-2.11.7.jar:na]
at scala.concurrent.impl.Promise$DefaultPromise.complete(Promise.scala:153) [scala-library-2.11.7.jar:na]
at scala.concurrent.impl.Future$PromiseCompletingRunnable.run(Future.scala:23) [scala-library-2.11.7.jar:na]
at akka.dispatch.TaskInvocation.run(AbstractDispatcher.scala:40) [akka-actor_2.11-2.3.13.jar:na]
at akka.dispatch.ForkJoinExecutorConfigurator$AkkaForkJoinTask.exec(AbstractDispatcher.scala:397) [akka-actor_2.11-2.3.13.jar:na]
at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260) [scala-library-2.11.7.jar:na]
at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339) [scala-library-2.11.7.jar:na]
at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979) [scala-library-2.11.7.jar:na]
at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107) [scala-library-2.11.7.jar:na]
Caused by: org.elasticsearch.client.transport.NoNodeAvailableException: None of the configured nodes are available: [{#transport#-1}{127.0.0.1}{127.0.0.1:9300}]
at org.elasticsearch.client.transport.TransportClientNodesService.ensureNodesAreAvailable(TransportClientNodesService.java:290) ~[elasticsearch-2.2.0.jar:2.2.0]
at org.elasticsearch.client.transport.TransportClientNodesService.execute(TransportClientNodesService.java:207) ~[elasticsearch-2.2.0.jar:2.2.0]
at org.elasticsearch.client.transport.support.TransportProxyClient.execute(TransportProxyClient.java:55) ~[elasticsearch-2.2.0.jar:2.2.0]
at org.elasticsearch.client.transport.TransportClient.doExecute(TransportClient.java:286) ~[elasticsearch-2.2.0.jar:2.2.0]
at org.elasticsearch.client.support.AbstractClient.execute(AbstractClient.java:351) ~[elasticsearch-2.2.0.jar:2.2.0]
at org.elasticsearch.client.support.AbstractClient$ClusterAdmin.execute(AbstractClient.java:845) ~[elasticsearch-2.2.0.jar:2.2.0]
at org.elasticsearch.action.ActionRequestBuilder.execute(ActionRequestBuilder.java:85) ~[elasticsearch-2.2.0.jar:2.2.0]
at com.sksamuel.elastic4s.admin.ClusterDsl$ClusterStatsExecutable$$anonfun$apply$2.apply(ClusterDsl.scala:24) ~[elastic4s-core_2.11-2.2.0.jar:2.2.0]
at com.sksamuel.elastic4s.admin.ClusterDsl$ClusterStatsExecutable$$anonfun$apply$2.apply(ClusterDsl.scala:24) ~[elastic4s-core_2.11-2.2.0.jar:2.2.0]
at com.sksamuel.elastic4s.Executable$class.injectFuture(Executable.scala:30) ~[elastic4s-core_2.11-2.2.0.jar:2.2.0]
at com.sksamuel.elastic4s.admin.ClusterDsl$ClusterStatsExecutable$.injectFuture(ClusterDsl.scala:21) ~[elastic4s-core_2.11-2.2.0.jar:2.2.0]
at com.sksamuel.elastic4s.admin.ClusterDsl$ClusterStatsExecutable$.apply(ClusterDsl.scala:24) ~[elastic4s-core_2.11-2.2.0.jar:2.2.0]
at com.sksamuel.elastic4s.admin.ClusterDsl$ClusterStatsExecutable$.apply(ClusterDsl.scala:21) ~[elastic4s-core_2.11-2.2.0.jar:2.2.0]
at com.sksamuel.elastic4s.ElasticClient.execute(ElasticClient.scala:20) ~[elastic4s-core_2.11-2.2.0.jar:2.2.0]
at controllers.BookController$ElasticConnection$.eagerStats(BookController.scala:35) ~[classes/:na]
at controllers.BookController$$anonfun$eagerStats$1.apply(BookController.scala:41) ~[classes/:na]
at controllers.BookController$$anonfun$eagerStats$1.apply(BookController.scala:41) ~[classes/:na]
at play.api.mvc.ActionBuilder$$anonfun$async$1.apply(Action.scala:456) ~[play_2.11-2.4.6.jar:2.4.6]
at play.api.mvc.ActionBuilder$$anonfun$async$1.apply(Action.scala:456) ~[play_2.11-2.4.6.jar:2.4.6]
at play.api.mvc.Action$.invokeBlock(Action.scala:533) ~[play_2.11-2.4.6.jar:2.4.6]
at play.api.mvc.Action$.invokeBlock(Action.scala:530) ~[play_2.11-2.4.6.jar:2.4.6]
at play.api.mvc.ActionBuilder$$anon$1.apply(Action.scala:493) ~[play_2.11-2.4.6.jar:2.4.6]
at play.api.mvc.Action$$anonfun$apply$1$$anonfun$apply$4$$anonfun$apply$5.apply(Action.scala:105) ~[play_2.11-2.4.6.jar:2.4.6]
at play.api.mvc.Action$$anonfun$apply$1$$anonfun$apply$4$$anonfun$apply$5.apply(Action.scala:105) ~[play_2.11-2.4.6.jar:2.4.6]
at play.utils.Threads$.withContextClassLoader(Threads.scala:21) ~[play_2.11-2.4.6.jar:2.4.6]
at play.api.mvc.Action$$anonfun$apply$1$$anonfun$apply$4.apply(Action.scala:104) ~[play_2.11-2.4.6.jar:2.4.6]
at play.api.mvc.Action$$anonfun$apply$1$$anonfun$apply$4.apply(Action.scala:103) ~[play_2.11-2.4.6.jar:2.4.6]
at scala.Option.map(Option.scala:146) ~[scala-library-2.11.7.jar:na]
at play.api.mvc.Action$$anonfun$apply$1.apply(Action.scala:103) ~[play_2.11-2.4.6.jar:2.4.6]
at play.api.mvc.Action$$anonfun$apply$1.apply(Action.scala:96) ~[play_2.11-2.4.6.jar:2.4.6]
at play.api.libs.iteratee.DoneIteratee$$anonfun$mapM$2.apply(Iteratee.scala:741) ~[play-iteratees_2.11-2.4.6.jar:2.4.6]
at play.api.libs.iteratee.DoneIteratee$$anonfun$mapM$2.apply(Iteratee.scala:741) ~[play-iteratees_2.11-2.4.6.jar:2.4.6]
at scala.concurrent.impl.Future$PromiseCompletingRunnable.liftedTree1$1(Future.scala:24) [scala-library-2.11.7.jar:na]
at scala.concurrent.impl.Future$PromiseCompletingRunnable.run(Future.scala:24) [scala-library-2.11.7.jar:na]
... 6 common frames omitted

1 个答案:

答案 0 :(得分：1)

事实证明这是一种奇怪的竞争条件，所以你现在也可以停止阅读。

以下是我对发生的事情的假设：

竞争条件是由ES java驱动程序处理连接的方式引起的， 并且与Play或elastic4s无关。

在建立连接之前，

ElasticClient.transport(...)不会阻止;它只使用给定的设置初始化驱动程序。这会导致驱动程序尝试连接到ES群集，但连接尝试在引擎盖下是异步的。如果驱动程序在请求任何API调用之前设法建立连接，则一切正常。另一方面，如果在驱动程序初始化之后立即进行任何API调用且尚未建立连接，则API调用将失败并出现此确切异常。在通常情况下，这一切都发生得非常快，并没有造成任何麻烦。我怀疑从交互式sbt会话运行会增加复杂性，因为Play自动加载 - 内存有限（部分由SBT本身消耗），而JVM负载很重，因为编译，Play引导程序和ES连接init都是根据请求发生的。 / p>

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