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https://issues.apache.org/jira/browse/KAFKA-1414?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14065034#comment-14065034
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Jun Rao commented on KAFKA-1414:
--------------------------------
Thanks for patch v3. A few more comments.
30. No need to pass in recoverThreads and shutdownThreads to LogConfig.
31. LogManagerTest: Could we move createLogManager to TestUtils? Then we can
reuse it in other places like ReplicaMangerTest as well.
32. LogManager
32.1 loadLogs(): I overlooked this in the previous review. Similar to shutdown,
the parallelization here needs to be done at the log level, instead of log dir
level. This will help the case when a single log dir is built on a multi-disk
volume.
33. shutdown(): The patch waits until all logs in each log dir are closed
before moving to the next log dir. Would it be better to submit the job for all
logs in all log dir first and then do the wait? This will allows us to use all
log dirs in parallel. The downside is that if we hit an IOException in one of
the log dirs, we won't be able write the recovery and the cleanShudown file in
other logDirs. However, that's the current behavior anyway.
34. For Jay's comment, I suspect that both startup and shutdown time are
dominated by I/O. So, it probably makes sense to use a single config for both
startup and shutdown.
> Speedup broker startup after hard reset
> ---------------------------------------
>
> Key: KAFKA-1414
> URL: https://issues.apache.org/jira/browse/KAFKA-1414
> Project: Kafka
> Issue Type: Improvement
> Components: log
> Affects Versions: 0.8.2, 0.9.0, 0.8.1.1
> Reporter: Dmitry Bugaychenko
> Assignee: Jay Kreps
> Attachments:
> 0001-KAFKA-1414-Speedup-broker-startup-after-hard-reset-a.patch,
> KAFKA-1414-rev1.patch, parallel-dir-loading-0.8.patch,
> parallel-dir-loading-trunk-fixed-threadpool.patch,
> parallel-dir-loading-trunk-threadpool.patch, parallel-dir-loading-trunk.patch
>
>
> After hard reset due to power failure broker takes way too much time
> recovering unflushed segments in a single thread. This could be easiliy
> improved launching multiple threads (one per data dirrectory, assuming that
> typically each data directory is on a dedicated drive). Localy we trie this
> simple patch to LogManager.loadLogs and it seems to work, however I'm too new
> to scala, so do not take it literally:
> {code}
> /**
> * Recover and load all logs in the given data directories
> */
> private def loadLogs(dirs: Seq[File]) {
> val threads : Array[Thread] = new Array[Thread](dirs.size)
> var i: Int = 0
> val me = this
> for(dir <- dirs) {
> val thread = new Thread( new Runnable {
> def run()
> {
> val recoveryPoints = me.recoveryPointCheckpoints(dir).read
> /* load the logs */
> val subDirs = dir.listFiles()
> if(subDirs != null) {
> val cleanShutDownFile = new File(dir, Log.CleanShutdownFile)
> if(cleanShutDownFile.exists())
> info("Found clean shutdown file. Skipping recovery for all logs
> in data directory '%s'".format(dir.getAbsolutePath))
> for(dir <- subDirs) {
> if(dir.isDirectory) {
> info("Loading log '" + dir.getName + "'")
> val topicPartition = Log.parseTopicPartitionName(dir.getName)
> val config = topicConfigs.getOrElse(topicPartition.topic,
> defaultConfig)
> val log = new Log(dir,
> config,
> recoveryPoints.getOrElse(topicPartition, 0L),
> scheduler,
> time)
> val previous = addLogWithLock(topicPartition, log)
> if(previous != null)
> throw new IllegalArgumentException("Duplicate log
> directories found: %s, %s!".format(log.dir.getAbsolutePath,
> previous.dir.getAbsolutePath))
> }
> }
> cleanShutDownFile.delete()
> }
> }
> })
> thread.start()
> threads(i) = thread
> i = i + 1
> }
> for(thread <- threads) {
> thread.join()
> }
> }
> def addLogWithLock(topicPartition: TopicAndPartition, log: Log): Log = {
> logCreationOrDeletionLock synchronized {
> this.logs.put(topicPartition, log)
> }
> }
> {code}
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