[GitHub] spark pull request: [SPARK-7889] [CORE] HistoryServer to refresh c...

[squito <gi...@git.apache.org>]

Github user squito commented on a diff in the pull request:

    https://github.com/apache/spark/pull/6935#discussion_r46989032
  
    --- Diff: core/src/main/scala/org/apache/spark/deploy/history/ApplicationCache.scala ---
    @@ -0,0 +1,648 @@
    +/*
    + * 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 java.util.NoSuchElementException
    +
    +import javax.servlet.http.{HttpServletRequest, HttpServletResponse}
    +import javax.servlet.{DispatcherType, Filter, FilterChain, FilterConfig, ServletException, ServletRequest, ServletResponse}
    +
    +import scala.collection.JavaConverters._
    +
    +import com.codahale.metrics.{Counter, MetricRegistry, Timer}
    +import com.google.common.cache.{CacheBuilder, CacheLoader, LoadingCache, RemovalListener, RemovalNotification}
    +import org.eclipse.jetty.servlet.FilterHolder
    +
    +import org.apache.spark.Logging
    +import org.apache.spark.metrics.source.Source
    +import org.apache.spark.ui.SparkUI
    +import org.apache.spark.util.Clock
    +
    +/**
    + * Cache for applications.
    + *
    + * Completed applications are cached for as long as there is capacity for them.
    + * Incompleted applications have their update time checked on every
    + * retrieval; if the cached entry is out of date, it is refreshed.
    + *
    + * @note there must be only one instance of [[ApplicationCache]] in a
    + * JVM at a time. This is because a static field in [[ApplicationCacheCheckFilterRelay]]
    + * keeps a reference to the cache so that HTTP requests on the attempt-specific web UIs
    + * can probe the current cache to see if the attempts have changed.
    + *
    + * Creating multiple instances will break this routing.
    + * @param operations implementation of record access operations
    + * @param refreshInterval interval between refreshes in milliseconds.
    + * @param retainedApplications number of retained applications
    + * @param clock time source
    + */
    +private[history] class ApplicationCache(val operations: ApplicationCacheOperations,
    +    val refreshInterval: Long,
    +    val retainedApplications: Int,
    +    val clock: Clock) extends Logging {
    +
    +  /**
    +   * Services the load request from the cache.
    +   */
    +  private val appLoader = new CacheLoader[CacheKey, CacheEntry] {
    +
    +    /** the cache key doesn't match an cached entry ... attempt to load it  */
    +    override def load(key: CacheKey): CacheEntry = {
    +      loadApplicationEntry(key.appId, key.attemptId)
    +    }
    +
    +  }
    +
    +  /**
    +   * Handler for callbacks from the cache of entry removal.
    +   */
    +  private val removalListener = new RemovalListener[CacheKey, CacheEntry] {
    +
    +    /**
    +     * Removal event notifies the provider to detach the UI.
    +     * @param rm removal notification
    +     */
    +    override def onRemoval(rm: RemovalNotification[CacheKey, CacheEntry]): Unit = {
    +      metrics.evictionCount.inc()
    +      val key = rm.getKey
    +      logDebug(s"Evicting entry ${key}")
    +      operations.detachSparkUI(key.appId, key.attemptId, rm.getValue().ui)
    +    }
    +  }
    +
    +  /**
    +   * The cache of applications.
    +   *
    +   * Tagged as `protected` so as to allow subclasses in tests to accesss it directly
    +   */
    +  protected val appCache: LoadingCache[CacheKey, CacheEntry] = CacheBuilder.newBuilder()
    +      .maximumSize(retainedApplications)
    +      .removalListener(removalListener)
    +      .build(appLoader)
    +
    +  /**
    +   * The metrics which are updated as the cache is used
    +   */
    +  val metrics = new CacheMetrics("history.cache")
    +
    +  init()
    +
    +  /**
    +   * Perform any startup operations.
    +   *
    +   * This includes declaring this instance as the cache to use in the
    +   * [[ApplicationCacheCheckFilterRelay]].
    +   */
    +  private def init(): Unit = {
    +    ApplicationCacheCheckFilterRelay.setApplicationCache(this)
    +  }
    +
    +  /**
    +   * Stop the cache.
    +   * This will reset the relay in [[ApplicationCacheCheckFilterRelay]].
    +   */
    +  def stop(): Unit = {
    +    ApplicationCacheCheckFilterRelay.resetApplicationCache()
    +  }
    +
    +  /**
    +   * Get an entry. Cache fetch/refresh will have taken place by
    +   * the time this method returns.
    +   * @param appAndAttempt application to look up in the format needed by the history server web UI,
    +   *                      `appId/attemptId` or `appId`.
    +   * @return the entry
    +   */
    +  def get(appAndAttempt: String): SparkUI = {
    +    val parts = splitAppAndAttemptKey(appAndAttempt)
    +    get(parts._1, parts._2)
    +  }
    +
    +  /**
    +   * Get the associated spark UI. Cache fetch/refresh will have taken place by
    +   * the time this method returns.
    +   * @param appId application ID
    +   * @param attemptId optional attempt ID
    +   * @return the entry
    +   */
    +  def get(appId: String, attemptId: Option[String]): SparkUI = {
    +    lookupAndUpdate(appId, attemptId)._1.ui
    +  }
    +
    +  /**
    +   * Look up the entry; update it if needed.
    +   * @param appId application ID
    +   * @param attemptId optional attempt ID
    +   * @return the underlying cache entry -which can have its timestamp changed, and a flag to
    +   *         indicate that the entry has changed
    +   */
    +  private def lookupAndUpdate(appId: String, attemptId: Option[String]): (CacheEntry, Boolean) = {
    +    metrics.lookupCount.inc()
    +    val cacheKey = CacheKey(appId, attemptId)
    +    var entry = appCache.getIfPresent(cacheKey)
    +    var updated = false
    +    if (entry == null) {
    +      // no entry, so fetch without any post-fetch probes for out-of-dateness
    +      entry = appCache.get(cacheKey)
    +    } else if (!entry.completed) {
    +      val now = clock.getTimeMillis()
    +      if (now - entry.probeTime > refreshInterval) {
    +        log.debug(s"Probing @time $now for updated application $cacheKey -> $entry")
    +        metrics.updateProbeCount.inc()
    +        updated = time(metrics.updateProbeTimer) {
    +          operations.isUpdated(appId, attemptId, entry.loadTime, entry.data)
    +        }
    +        if (updated) {
    +          logDebug(s"refreshing $cacheKey")
    +          metrics.updateTriggeredCount.inc()
    +          appCache.refresh(cacheKey)
    +          // and repeat the lookup
    +          entry = appCache.get(cacheKey)
    +        } else {
    +          // update the probe timestamp to the current time
    +          entry.probeTime = now
    +        }
    +      }
    +    }
    +    (entry, updated)
    +  }
    +
    +  /**
    +   * This method is visible for testing. It looks up the cached entry *and returns a clone of it*.
    +   * This ensures that the cached entries never leak
    +   * @param appId application ID
    +   * @param attemptId optional attempt ID
    +   * @return a new entry with shared SparkUI, but copies of the other fields.
    +   */
    +  def lookupCacheEntry(appId: String, attemptId: Option[String]): CacheEntry = {
    +    val entry = lookupAndUpdate(appId, attemptId)._1
    +    new CacheEntry(entry.ui, entry.completed, entry.data, entry.loadTime, entry.probeTime)
    +  }
    +
    +  /**
    +   * Probe for an application being updated
    +   * @param appId application ID
    +   * @param attemptId attempt ID
    +   * @return true if an update has been triggered
    +   */
    +  def checkForUpdates(appId: String, attemptId: Option[String]): Boolean = {
    +    val (entry, updated) = lookupAndUpdate(appId, attemptId)
    +    updated
    +  }
    +
    +  /**
    +   * Size probe, primarily for testing
    +   * @return size
    +   */
    +  def size(): Long = appCache.size()
    +
    +  /**
    +   * Emptiness predicate, primarily for testing
    +   * @return true if the cache is empty
    +   */
    +  def isEmpty: Boolean = appCache.size() == 0
    +
    +  /**
    +   * Time a closure, returning its output.
    +   * @param t timer
    +   * @param f function
    +   * @tparam T type of return value of time
    +   * @return the result of the function.
    +   */
    +  private def time[T](t: Timer)(f: => T): T = {
    +    val timeCtx = t.time()
    +    try {
    +      f
    +    } finally {
    +      timeCtx.close()
    +    }
    +  }
    +
    +  /**
    +   * Load the Spark UI via [[ApplicationCacheOperations.getAppUI()]],
    +   * then attach it to the web UI via [[ApplicationCacheOperations.attachSparkUI()]].
    +   * If the application is incomplete, it has the [[ApplicationCacheCheckFilter]]
    +   * added as a filter to the HTTP requests, so that queries on the UI will trigger
    +   * update checks.
    +   *
    +   * The generated entry contains the UI and the current timestamp.
    +   * The timer [[metrics.loadTimer]] tracks the time taken to load the UI.
    +   *
    +   * @param appId application ID
    +   * @param attemptId optional attempt ID
    +   * @return the cache entry
    +   * @throws NoSuchElementException if there is no matching element
    +   */
    +  @throws[NoSuchElementException]
    +  def loadApplicationEntry(appId: String, attemptId: Option[String]): CacheEntry = {
    +
    +    logDebug(s"Loading application Entry $appId/$attemptId")
    +    metrics.loadCount.inc()
    +    time(metrics.loadTimer) {
    +      operations.getAppUI(appId, attemptId) match {
    +        case Some(LoadedAppUI(ui, loadTime, data)) =>
    +          val completed = ui.getApplicationInfoList.exists(_.attempts.last.completed)
    +          if (completed) {
    +            // completed spark UIs are attached directly
    +            operations.attachSparkUI(appId, attemptId, ui, completed)
    +          } else {
    +            // incomplete UIs have the cache-check filter put in front of them.
    +            ApplicationCacheCheckFilterRelay.registerFilter(ui, appId, attemptId)
    +            operations.attachSparkUI(appId, attemptId, ui, completed)
    +          }
    +          // build the cache entry
    +          val now = clock.getTimeMillis()
    +          val entry = new CacheEntry(ui, completed, data, if (loadTime> 0) loadTime else now , now)
    +          logDebug(s"Loaded application $appId/$attemptId -> $entry")
    +          entry
    +        case None =>
    +          metrics.lookupFailureCount.inc()
    +          // guava's cache logs via java.util log, so is of limited use. Hence: our own message
    +          logInfo(s"Failed to load application attempt $appId/$attemptId")
    +          throw new NoSuchElementException(s"no application with application Id '$appId'" +
    +              attemptId.map { id => s" attemptId '$id'" }.getOrElse(" and no attempt Id"))
    +      }
    +    }
    +  }
    +
    +  /**
    +   * Split up an `applicationId/attemptId` or `applicationId` key into the separate pieces.
    +   *
    +   * @param appAndAttempt combined key
    +   * @return a tuple of the application ID and, if present, the attemptID
    +   */
    +  def splitAppAndAttemptKey(appAndAttempt: String): (String, Option[String]) = {
    +    val parts = appAndAttempt.split("/")
    +    require(parts.length == 1 || parts.length == 2, s"Invalid app key $appAndAttempt")
    +    val appId = parts(0)
    +    val attemptId = if (parts.length > 1) Some(parts(1)) else None
    +    (appId, attemptId)
    +  }
    +
    +  /**
    +   * Merge an appId and optional attempt Id into a key of the form `applicationId/attemptId`
    +   * if there is an `attemptId`; `applicationId` if not.
    +   * @param appId application ID
    +   * @param attemptId optional attempt ID
    +   * @return a unified string
    +   */
    +  def mergeAppAndAttemptToKey(appId: String, attemptId: Option[String]): String = {
    +    appId + attemptId.map { id => s"/$id" }.getOrElse("")
    +  }
    +
    +  /**
    +   * String operator dumps the cache entries and metrics.
    +   * @return a string value, primarily for testing and diagnostics
    +   */
    +  override def toString: String = {
    +    val sb = new StringBuilder(s"ApplicationCache(refreshInterval=$refreshInterval," +
    +          s" retainedApplications= $retainedApplications)")
    +    sb.append(s"; time= ${clock.getTimeMillis()}")
    +    sb.append(s"; entry count= ${appCache.size()}\n")
    +    sb.append("----\n")
    +    appCache.asMap().asScala.foreach {
    +      case(key, entry) => sb.append(s"  $key -> $entry\n")
    +    }
    +    sb.append("----\n")
    +    sb.append(metrics)
    +    sb.append("----\n")
    +    sb.toString()
    +  }
    +}
    +
    +/**
    + * An entry in the cache.
    + *
    + * @param ui Spark UI
    + * @param completed: flag to indicated that the application has completed (and so
    + *                 does not need refreshing)
    + * @param probeTime timestamp in milliseconds. This may be updated during probes
    + */
    +private[history] final class CacheEntry(val ui: SparkUI, val completed: Boolean,
    +    val data: Option[HistoryProviderUpdateState],
    +    val loadTime: Long,
    +    var probeTime: Long) {
    +
    +  /** string value is for test assertions */
    +  override def toString: String = {
    +    s"UI $ui, data=$data, completed=$completed, loadTime=$loadTime probeTime=$probeTime"
    +  }
    +}
    +
    +/**
    + * Cache key: compares on App Id and then, if non-empty, attemptId.
    + * The [[hashCode()]] function uses the same fields.
    + * @param appId application ID
    + * @param attemptId attempt ID
    + */
    +private[history] final case class CacheKey(appId: String, attemptId: Option[String]) {
    +
    +  override def hashCode(): Int = {
    +    appId.hashCode() + attemptId.map(_.hashCode).getOrElse(0)
    +  }
    +
    +  override def equals(obj: Any): Boolean = {
    +    val that = obj.asInstanceOf[CacheKey]
    +    that.appId == appId && that.attemptId == attemptId
    +  }
    +
    +  override def toString: String = {
    +    appId + attemptId.map { id => s"/$id" }.getOrElse("")
    +  }
    +}
    +
    +private[history] class CacheMetrics(prefix: String) extends Source {
    +
    +  /* metrics: counters and timers */
    +  val lookupCount = new Counter()
    +  val lookupFailureCount = new Counter()
    +  val evictionCount = new Counter()
    +  val loadCount = new Counter()
    +  val loadTimer = new Timer()
    +  val updateProbeCount = new Counter()
    +  val updateProbeTimer = new Timer()
    +  val updateTriggeredCount = new Counter()
    +
    +  /** all the counters: for registration and string conversion. */
    +  private val counters = Seq(
    +    ("lookup.count", lookupCount),
    +    ("lookup.failure.count", lookupFailureCount),
    +    ("eviction.count", evictionCount),
    +    ("load.count", loadCount),
    +    ("update.probe.count", updateProbeCount),
    +    ("update.triggered.count", updateTriggeredCount))
    +
    +  /** all metrics, including timers */
    +  private val allMetrics = counters ++ Seq(
    +    ("load.timer", loadTimer),
    +    ("update.probe.timer", updateProbeTimer))
    +
    +  /**
    +   * Name of metric source
    +   */
    +  override val sourceName = "ApplicationCache"
    +
    +  override def metricRegistry: MetricRegistry = new MetricRegistry
    --- End diff --
    
    I think you want to store this in a `val` and not return a new one on every call


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