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LocalSnapshotStore.scala
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LocalSnapshotStore.scala
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/**
* Copyright (C) 2009-2018 Lightbend Inc. <https://www.lightbend.com>
* Copyright (C) 2012-2016 Eligotech BV.
*/
package akka.persistence.snapshot.local
import java.io._
import java.net.{ URLDecoder, URLEncoder }
import akka.actor.ActorLogging
import akka.persistence._
import akka.persistence.serialization._
import akka.persistence.snapshot._
import akka.serialization.SerializationExtension
import akka.util.ByteString.UTF_8
import com.typesafe.config.Config
import scala.collection.immutable
import scala.concurrent.Future
import scala.util._
import java.nio.file.Files
/**
* INTERNAL API
*
* Local filesystem backed snapshot store.
*/
private[persistence] class LocalSnapshotStore(config: Config) extends SnapshotStore with ActorLogging {
private val FilenamePattern = """^snapshot-(.+)-(\d+)-(\d+)""".r
private val persistenceIdStartIdx = 9 // Persistence ID starts after the "snapshot-" substring
import akka.util.Helpers._
private val maxLoadAttempts = config.getInt("max-load-attempts")
.requiring(_ > 1, "max-load-attempts must be >= 1")
private val streamDispatcher = context.system.dispatchers.lookup(config.getString("stream-dispatcher"))
private val dir = new File(config.getString("dir"))
private val serializationExtension = SerializationExtension(context.system)
private var saving = immutable.Set.empty[SnapshotMetadata] // saving in progress
override def loadAsync(persistenceId: String, criteria: SnapshotSelectionCriteria): Future[Option[SelectedSnapshot]] = {
//
// Heuristics:
//
// Select youngest `maxLoadAttempts` snapshots that match upper bound.
// This may help in situations where saving of a snapshot could not be completed because of a JVM crash.
// Hence, an attempt to load that snapshot will fail but loading an older snapshot may succeed.
//
val metadata = snapshotMetadatas(persistenceId, criteria).sorted.takeRight(maxLoadAttempts)
Future {
load(metadata) match {
case Success(s) ⇒ s
case Failure(e) ⇒ throw e // all attempts failed, fail the future
}
}(streamDispatcher)
}
override def saveAsync(metadata: SnapshotMetadata, snapshot: Any): Future[Unit] = {
saving += metadata
val completion = Future(save(metadata, snapshot))(streamDispatcher)
completion
}
override def deleteAsync(metadata: SnapshotMetadata): Future[Unit] = {
saving -= metadata
Future {
// multiple snapshot files here mean that there were multiple snapshots for this seqNr, we delete all of them
// usually snapshot-stores would keep one snapshot per sequenceNr however here in the file-based one we timestamp
// snapshots and allow multiple to be kept around (for the same seqNr) if desired
snapshotFiles(metadata).map(_.delete())
}(streamDispatcher).map(_ ⇒ ())(streamDispatcher)
}
override def deleteAsync(persistenceId: String, criteria: SnapshotSelectionCriteria): Future[Unit] = {
val metadatas = snapshotMetadatas(persistenceId, criteria)
Future.sequence {
metadatas.map(deleteAsync)
}(collection.breakOut, streamDispatcher).map(_ ⇒ ())(streamDispatcher)
}
override def receivePluginInternal: Receive = {
case SaveSnapshotSuccess(metadata) ⇒ saving -= metadata
case _: SaveSnapshotFailure ⇒ // ignore
case _: DeleteSnapshotsSuccess ⇒ // ignore
case _: DeleteSnapshotsFailure ⇒ // ignore
}
private def snapshotFiles(metadata: SnapshotMetadata): immutable.Seq[File] = {
snapshotDir.listFiles(new SnapshotSeqNrFilenameFilter(metadata)).toVector
}
@scala.annotation.tailrec
private def load(metadata: immutable.Seq[SnapshotMetadata]): Try[Option[SelectedSnapshot]] = metadata.lastOption match {
case None ⇒ Success(None) // no snapshots stored
case Some(md) ⇒
Try(withInputStream(md)(deserialize)) match {
case Success(s) ⇒
Success(Some(SelectedSnapshot(md, s.data)))
case Failure(e) ⇒
val remaining = metadata.init
log.error(e, s"Error loading snapshot [{}], remaining attempts: [{}]", md, remaining.size)
if (remaining.isEmpty)
Failure(e) // all attempts failed
else
load(remaining) // try older snapshot
}
}
protected def save(metadata: SnapshotMetadata, snapshot: Any): Unit = {
val tmpFile = withOutputStream(metadata)(serialize(_, Snapshot(snapshot)))
tmpFile.renameTo(snapshotFileForWrite(metadata))
}
protected def deserialize(inputStream: InputStream): Snapshot =
serializationExtension.deserialize(streamToBytes(inputStream), classOf[Snapshot]).get
protected def serialize(outputStream: OutputStream, snapshot: Snapshot): Unit = {
outputStream.write(serializationExtension.serialize(snapshot).get)
}
protected def withOutputStream(metadata: SnapshotMetadata)(p: (OutputStream) ⇒ Unit): File = {
val tmpFile = snapshotFileForWrite(metadata, extension = "tmp")
withStream(new BufferedOutputStream(Files.newOutputStream(tmpFile.toPath())), p)
tmpFile
}
private def withInputStream[T](metadata: SnapshotMetadata)(p: (InputStream) ⇒ T): T =
withStream(new BufferedInputStream(Files.newInputStream(snapshotFileForWrite(metadata).toPath())), p)
private def withStream[A <: Closeable, B](stream: A, p: A ⇒ B): B =
try { p(stream) } finally { stream.close() }
/** Only by persistenceId and sequenceNr, timestamp is informational - accomodates for 2.13.x series files */
protected def snapshotFileForWrite(metadata: SnapshotMetadata, extension: String = ""): File =
new File(snapshotDir, s"snapshot-${URLEncoder.encode(metadata.persistenceId, UTF_8)}-${metadata.sequenceNr}-${metadata.timestamp}${extension}")
private def snapshotMetadatas(persistenceId: String, criteria: SnapshotSelectionCriteria): immutable.Seq[SnapshotMetadata] = {
val files = snapshotDir.listFiles(new SnapshotFilenameFilter(persistenceId))
if (files eq null) Nil // if the dir was removed
else {
files.map(_.getName).flatMap { filename ⇒
extractMetadata(filename).map {
case (pid, snr, tms) ⇒ SnapshotMetadata(URLDecoder.decode(pid, UTF_8), snr, tms)
}
}.filter(md ⇒ criteria.matches(md) && !saving.contains(md)).toVector
}
}
override def preStart() {
snapshotDir()
super.preStart()
}
private def snapshotDir(): File = {
if (!dir.isDirectory) {
// try to create the directory, on failure double check if someone else beat us to it
if (!dir.mkdirs() && !dir.isDirectory) {
throw new IOException(s"Failed to create snapshot directory [${dir.getCanonicalPath}]")
}
}
dir
}
private final class SnapshotFilenameFilter(persistenceId: String) extends FilenameFilter {
val encodedPersistenceId = URLEncoder.encode(persistenceId)
def accept(dir: File, name: String): Boolean = {
val persistenceIdEndIdx = name.lastIndexOf('-', name.lastIndexOf('-') - 1)
persistenceIdStartIdx + encodedPersistenceId.length == persistenceIdEndIdx &&
name.startsWith(encodedPersistenceId, persistenceIdStartIdx)
}
}
private final class SnapshotSeqNrFilenameFilter(md: SnapshotMetadata) extends FilenameFilter {
private final def matches(pid: String, snr: String, tms: String): Boolean = {
pid.equals(URLEncoder.encode(md.persistenceId)) &&
Try(snr.toLong == md.sequenceNr && (md.timestamp == 0L || tms.toLong == md.timestamp)).getOrElse(false)
}
def accept(dir: File, name: String): Boolean =
name match {
case FilenamePattern(pid, snr, tms) ⇒ matches(pid, snr, tms)
case _ ⇒ false
}
}
private def extractMetadata(filename: String): Option[(String, Long, Long)] = {
val sequenceNumberEndIdx = filename.lastIndexOf('-')
val persistenceIdEndIdx = filename.lastIndexOf('-', sequenceNumberEndIdx - 1)
val timestampString = filename.substring(sequenceNumberEndIdx + 1)
if (persistenceIdStartIdx >= persistenceIdEndIdx || timestampString.exists(!_.isDigit)) None
else {
val persistenceId = filename.substring(persistenceIdStartIdx, persistenceIdEndIdx)
val sequenceNumber = filename.substring(persistenceIdEndIdx + 1, sequenceNumberEndIdx).toLong
val timestamp = filename.substring(sequenceNumberEndIdx + 1).toLong
Some((persistenceId, sequenceNumber, timestamp))
}
}
}