Github user steveloughran commented on a diff in the pull request:
https://github.com/apache/spark/pull/8744#discussion_r43387678
--- Diff:
yarn/src/history/main/scala/org/apache/spark/deploy/history/yarn/YarnHistoryService.scala
---
@@ -0,0 +1,1328 @@
+/*
+ * 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.history.yarn
+
+import java.io.InterruptedIOException
+import java.net.{ConnectException, URI}
+import java.util.concurrent.atomic.{AtomicBoolean, AtomicInteger}
+import java.util.concurrent.{LinkedBlockingDeque, TimeUnit}
+
+import scala.collection.JavaConverters._
+import scala.collection.mutable
+
+import com.codahale.metrics.{Counter, MetricRegistry, Timer}
+import org.apache.hadoop.security.UserGroupInformation
+import org.apache.hadoop.yarn.api.records.timeline.{TimelineDomain,
TimelineEntity, TimelineEvent}
+import org.apache.hadoop.yarn.api.records.{ApplicationAttemptId,
ApplicationId}
+import org.apache.hadoop.yarn.client.api.TimelineClient
+import org.apache.hadoop.yarn.conf.YarnConfiguration
+
+import org.apache.spark.deploy.history.yarn.YarnTimelineUtils._
+import org.apache.spark.metrics.source.Source
+import org.apache.spark.scheduler._
+import org.apache.spark.scheduler.cluster.{SchedulerExtensionService,
SchedulerExtensionServiceBinding}
+import org.apache.spark.util.{SystemClock, Utils}
+import org.apache.spark.{Logging, SparkContext}
+
+/**
+ * A Yarn Extension Service to post lifecycle events to a registered YARN
Timeline Server.
+ *
+ * Posting algorithm
+ *
+ * 1. The service subscribes to all events coming from the Spark Context.
+ * 1. These events are serialized into JSON objects for publishing to the
timeline service through
+ * HTTP(S) posts.
+ * 1. Events are buffered into `pendingEvents` until a batch is aggregated
into a
+ * [[TimelineEntity]] for posting.
+ * 1. That aggregation happens when a lifecycle event (application
start/stop) takes place,
+ * or the number of pending events in a running application exceeds the
limit set in
+ * `spark.hadoop.yarn.timeline.batch.size`.
+ * 1. Posting operations take place in a separate thread from the spark
event listener.
+ * 1. If an attempt to post to the timeline server fails, the service
sleeps and then
+ * it is re-attempted after the retry period defined by
+ * `spark.hadoop.yarn.timeline.post.retry.interval`.
+ * 1. If the number of events buffered in the history service exceed the
limit set in
+ * `spark.hadoop.yarn.timeline.post.limit`, then further events other than
application start/stop
+ * are dropped.
+ * 1. When the service is stopped, it will make a best-effort attempt to
post all queued events.
+ * the call of [[stop()]] can block up to the duration of
+ * `spark.hadoop.yarn.timeline.shutdown.waittime` for this to take place.
+ * 1. No events are posted until the service receives a
[[SparkListenerApplicationStart]] event.
+ *
+ * If the spark context has a metrics registry, then the internal counters
of queued entities,
+ * post failures and successes, and the performance of the posting
operation are all registered
+ * as metrics.
+ *
+ * The shutdown logic is somewhat convoluted, as the posting thread may be
blocked on HTTP IO
+ * when the shutdown process begins. In this situation, the thread
continues to be blocked, and
+ * will be interrupted once the wait time has expired. All time consumed
during the ongoing
+ * operation will be counted as part of the shutdown time period.
+ */
+private[spark] class YarnHistoryService extends SchedulerExtensionService
+ with Logging with Source {
--- End diff --
OK, I'll pull out the counters into their source subclass
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