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/*
* 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.storage
import java.io.{Externalizable, IOException, ObjectInput, ObjectOutput}
/**
* Flags for controlling the storage of an RDD. Each StorageLevel records whether to use memory,
* whether to drop the RDD to disk if it falls out of memory, whether to keep the data in memory
* in a serialized format, and whether to replicate the RDD partitions on multiple nodes.
* The [[org.apache.spark.storage.StorageLevel$]] singleton object contains some static constants
* for commonly useful storage levels. To create your own storage level object, use the
* factory method of the singleton object (`StorageLevel(...)`).
*/
class StorageLevel private(
private var useDisk_ : Boolean,
private var useMemory_ : Boolean,
private var deserialized_ : Boolean,
private var replication_ : Int = 1)
extends Externalizable {
// TODO: Also add fields for caching priority, dataset ID, and flushing.
private def this(flags: Int, replication: Int) {
this((flags & 4) != 0, (flags & 2) != 0, (flags & 1) != 0, replication)
}
def this() = this(false, true, false) // For deserialization
def useDisk = useDisk_
def useMemory = useMemory_
def deserialized = deserialized_
def replication = replication_
assert(replication < 40, "Replication restricted to be less than 40 for calculating hashcodes")
override def clone(): StorageLevel = new StorageLevel(
this.useDisk, this.useMemory, this.deserialized, this.replication)
override def equals(other: Any): Boolean = other match {
case s: StorageLevel =>
s.useDisk == useDisk &&
s.useMemory == useMemory &&
s.deserialized == deserialized &&
s.replication == replication
case _ =>
false
}
def isValid = ((useMemory || useDisk) && (replication > 0))
def toInt: Int = {
var ret = 0
if (useDisk_) {
ret |= 4
}
if (useMemory_) {
ret |= 2
}
if (deserialized_) {
ret |= 1
}
return ret
}
override def writeExternal(out: ObjectOutput) {
out.writeByte(toInt)
out.writeByte(replication_)
}
override def readExternal(in: ObjectInput) {
val flags = in.readByte()
useDisk_ = (flags & 4) != 0
useMemory_ = (flags & 2) != 0
deserialized_ = (flags & 1) != 0
replication_ = in.readByte()
}
@throws(classOf[IOException])
private def readResolve(): Object = StorageLevel.getCachedStorageLevel(this)
override def toString: String =
"StorageLevel(%b, %b, %b, %d)".format(useDisk, useMemory, deserialized, replication)
override def hashCode(): Int = toInt * 41 + replication
def description : String = {
var result = ""
result += (if (useDisk) "Disk " else "")
result += (if (useMemory) "Memory " else "")
result += (if (deserialized) "Deserialized " else "Serialized")
result += "%sx Replicated".format(replication)
result
}
}
object StorageLevel {
val NONE = new StorageLevel(false, false, false)
val DISK_ONLY = new StorageLevel(true, false, false)
val DISK_ONLY_2 = new StorageLevel(true, false, false, 2)
val MEMORY_ONLY = new StorageLevel(false, true, true)
val MEMORY_ONLY_2 = new StorageLevel(false, true, true, 2)
val MEMORY_ONLY_SER = new StorageLevel(false, true, false)
val MEMORY_ONLY_SER_2 = new StorageLevel(false, true, false, 2)
val MEMORY_AND_DISK = new StorageLevel(true, true, true)
val MEMORY_AND_DISK_2 = new StorageLevel(true, true, true, 2)
val MEMORY_AND_DISK_SER = new StorageLevel(true, true, false)
val MEMORY_AND_DISK_SER_2 = new StorageLevel(true, true, false, 2)
/** Create a new StorageLevel object */
def apply(useDisk: Boolean, useMemory: Boolean, deserialized: Boolean, replication: Int = 1) =
getCachedStorageLevel(new StorageLevel(useDisk, useMemory, deserialized, replication))
/** Create a new StorageLevel object from its integer representation */
def apply(flags: Int, replication: Int) =
getCachedStorageLevel(new StorageLevel(flags, replication))
/** Read StorageLevel object from ObjectInput stream */
def apply(in: ObjectInput) = {
val obj = new StorageLevel()
obj.readExternal(in)
getCachedStorageLevel(obj)
}
private[spark]
val storageLevelCache = new java.util.concurrent.ConcurrentHashMap[StorageLevel, StorageLevel]()
private[spark] def getCachedStorageLevel(level: StorageLevel): StorageLevel = {
storageLevelCache.putIfAbsent(level, level)
storageLevelCache.get(level)
}
}
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