Github user mridulm commented on a diff in the pull request: https://github.com/apache/spark/pull/151#discussion_r10638435 --- Diff: core/src/main/scala/org/apache/spark/deploy/yarn/YarnAllocationHandlerMacro.scala --- @@ -0,0 +1,46 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +package org.apache.spark.deploy.yarn + +import scala.language.experimental.macros +import scala.reflect.macros.Context + +private[yarn] object YarnAllocationHandlerMacro { + def getAMResp(resp: Any): Any = macro getAMRespImpl + + /** + * From Hadoop CDH 4.4.0+ (2.1.0-beta), + * AMResponse is merged into AllocateResponse, + * so we don't need to call getAMResponse(), just use AllocateResponse directly. + * This macro will test the existence of AMResponse, + * and generate diffenert expressions. + * + * This macro now is only used in spark's alpha version of yarn api. + * It stays in the core project, for the two-stage compiling of + * the scala macro system. + */ + def getAMRespImpl(c: Context)(resp: c.Expr[Any]) = { + try { + import c.universe._ + c.mirror.staticClass("org.apache.hadoop.yarn.api.records.AMResponse") + c.Expr[Any](Apply(Select(resp.tree, newTermName("getAMResponse")), List())) + } catch { + case _: Throwable => resp + } --- End diff -- I would look at this as a very uncommon and temporary situation. We would need to continue supporting the old api for only a little while longer - after which we can remove the reflection stuff; and ideally, yarn should converge on a stable api soon enough. So until then, unfortunately, we have instability in our impl. On Sat, Mar 15, 2014 at 10:32 PM, gzm55 <notificati...@github.com> wrote: > In > core/src/main/scala/org/apache/spark/deploy/yarn/YarnAllocationHandlerMacro.scala: > > > + * so we don't need to call getAMResponse(), just use AllocateResponse directly. > > + * This macro will test the existence of AMResponse, > > + * and generate diffenert expressions. > > + * > > + * This macro now is only used in spark's alpha version of yarn api. > > + * It stays in the core project, for the two-stage compiling of > > + * the scala macro system. > > + */ > > + def getAMRespImpl(c: Context)(resp: c.Expr[Any]) = { > > + try { > > + import c.universe._ > > + c.mirror.staticClass("org.apache.hadoop.yarn.api.records.AMResponse") > > + c.Expr[Any](Apply(Select(resp.tree, newTermName("getAMResponse")), List())) > > + } catch { > > + case _: Throwable => resp > > + } > > I tried to use runtime refleciton, and found some difficults. because > amResp will have different type, I've to give it a duck type like > > AnyRef { > def getAllocatedContainers ... > def getAvailableResources ... > def getCompletedContainersStatuses ... > } > > or have to cache four reflection methods (the upper three plus > getAMResponse()). in the future, each time we introduce a method of > AMResponse/AllocateResponse, we'll have to make additional cache for it. > > -- > Reply to this email directly or view it on GitHub<https://github.com/apache/spark/pull/151/files#r10638121> > . >
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