Github user pwendell commented on a diff in the pull request:
https://github.com/apache/spark/pull/204#discussion_r11456820
--- Diff:
core/src/main/scala/org/apache/spark/deploy/history/HistoryServer.scala ---
@@ -0,0 +1,322 @@
+/*
+ * 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
+
+import javax.servlet.http.HttpServletRequest
+
+import scala.collection.mutable
+
+import org.apache.hadoop.fs.{FileStatus, Path}
+import org.eclipse.jetty.servlet.ServletContextHandler
+
+import org.apache.spark.{Logging, SecurityManager, SparkConf}
+import org.apache.spark.deploy.SparkUIContainer
+import org.apache.spark.ui.SparkUI
+import org.apache.spark.ui.JettyUtils._
+import org.apache.spark.util.Utils
+import org.apache.spark.scheduler.{ApplicationEventListener,
ReplayListenerBus}
+
+/**
+ * A web server that renders SparkUIs of finished applications.
+ *
+ * For the standalone mode, MasterWebUI already achieves this
functionality. Thus, the
+ * main use case of the HistoryServer is in other deploy modes (e.g. Yarn
or Mesos).
+ *
+ * The logging directory structure is as follows: Within the given base
directory, each
+ * application's event logs are maintained in the application's own
sub-directory. This
+ * is the same structure as maintained in the event log write code path in
+ * EventLoggingListener.
+ *
+ * @param baseLogDir The base directory in which event logs are found
+ * @param requestedPort The requested port to which this server is to be
bound
+ */
+class HistoryServer(
+ val baseLogDir: String,
+ requestedPort: Int,
+ conf: SparkConf)
+ extends SparkUIContainer("History Server") with Logging {
+
+ import HistoryServer._
+
+ private val fileSystem = Utils.getHadoopFileSystem(baseLogDir)
+ private val localHost = Utils.localHostName()
+ private val publicHost =
Option(System.getenv("SPARK_PUBLIC_DNS")).getOrElse(localHost)
+ private val port = requestedPort
+ private val securityManager = new SecurityManager(conf)
+ private val indexPage = new IndexPage(this)
+
+ // A timestamp of when the disk was last accessed to check for log
updates
+ private var lastLogCheckTime = -1L
+
+ // If an application is last updated after this threshold, then its UI
is retained
+ private var updateTimeThreshold = -1L
+
+ // Number of applications hidden from the UI because the application
limit has been reached
+ private var numApplicationsHidden = 0
+
+ @volatile private var stopped = false
+
+ /**
+ * A background thread that periodically checks for event log updates on
disk.
+ *
+ * If a log check is invoked manually in the middle of a period, this
thread re-adjusts the
+ * time at which it performs the next log check to maintain the same
period as before.
+ */
+ private val logCheckingThread = new Thread {
+ override def run() {
+ while (!stopped) {
+ val now = System.currentTimeMillis
+ if (now - lastLogCheckTime > UPDATE_INTERVAL_MS) {
+ checkForLogs()
+ Thread.sleep(UPDATE_INTERVAL_MS)
+ } else {
+ // If the user has manually checked for logs recently, wait until
+ // UPDATE_INTERVAL_MS after the last check time
+ Thread.sleep(lastLogCheckTime + UPDATE_INTERVAL_MS - now)
+ }
+ }
+ }
+ }
+
+ private val handlers = Seq[ServletContextHandler](
+ createStaticHandler(STATIC_RESOURCE_DIR, "/static"),
+ createServletHandler("/",
+ (request: HttpServletRequest) => indexPage.render(request),
securityMgr = securityManager)
+ )
+
+ // A mapping of application ID to its history information, which
includes the rendered UI
+ val appIdToInfo = mutable.HashMap[String, ApplicationHistoryInfo]()
+
+ /**
+ * Start the history server.
+ *
+ * This starts a background thread that periodically synchronizes
information displayed on
+ * this UI with the event logs in the provided base directory.
+ */
+ def start() {
+ logCheckingThread.start()
+ }
+
+ /** Bind to the HTTP server behind this web interface. */
+ override def bind() {
+ try {
+ serverInfo = Some(startJettyServer("0.0.0.0", port, handlers, conf))
+ logInfo("Started HistoryServer at http://%s:%d".format(publicHost,
boundPort))
+ } catch {
+ case e: Exception =>
+ logError("Failed to bind HistoryServer", e)
+ System.exit(1)
+ }
+ checkForLogs()
+ }
+
+ /**
+ * Check for any updates to event logs in the base directory. This is
only effective once
--- End diff --
This function is pretty complicated - would it make more sense to decouple
a few of the pieces into different functions? I think there are a few things
that are sort of independent.
1) Garbage collecting applications whose underlying logs have been deleted.
In this case by the way, would it be simpler to just not do this? Why not just
let these fall out of scope naturally when the limit is hit...
2) Detecting new applications which were not previously loaded, but should
be.
3) Loading applications which we've decided should be loaded.
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