Github user jerryshao commented on a diff in the pull request:
https://github.com/apache/spark/pull/5645#discussion_r29309292
--- Diff:
streaming/src/main/scala/org/apache/spark/streaming/util/WriteAheadLogUtils.scala
---
@@ -0,0 +1,129 @@
+/*
+ * 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.streaming.util
+
+import scala.util.control.NonFatal
+
+import org.apache.hadoop.conf.Configuration
+
+import org.apache.spark.util.Utils
+import org.apache.spark.{Logging, SparkConf, SparkException}
+
+/** A helper class with utility functions related to the WriteAheadLog
interface */
+private[streaming] object WriteAheadLogUtils extends Logging {
+ val RECEIVER_WAL_ENABLE_CONF_KEY =
"spark.streaming.receiver.writeAheadLog.enable"
+ val RECEIVER_WAL_CLASS_CONF_KEY =
"spark.streaming.receiver.writeAheadLog.class"
+ val RECEIVER_WAL_ROLLING_INTERVAL_CONF_KEY =
+ "spark.streaming.receiver.writeAheadLog.rollingIntervalSecs"
+ val RECEIVER_WAL_MAX_FAILURES_CONF_KEY =
"spark.streaming.receiver.writeAheadLog.maxFailures"
+
+ val DRIVER_WAL_CLASS_CONF_KEY =
"spark.streaming.driver.writeAheadLog.class"
+ val DRIVER_WAL_ROLLING_INTERVAL_CONF_KEY =
+ "spark.streaming.driver.writeAheadLog.rollingIntervalSecs"
+ val DRIVER_WAL_MAX_FAILURES_CONF_KEY =
"spark.streaming.driver.writeAheadLog.maxFailures"
+
+ val DEFAULT_ROLLING_INTERVAL_SECS = 60
+ val DEFAULT_MAX_FAILURES = 3
+
+ def enableReceiverLog(conf: SparkConf): Boolean = {
+ conf.getBoolean(RECEIVER_WAL_ENABLE_CONF_KEY, false)
+ }
+
+ def getRollingIntervalSecs(conf: SparkConf, isDriver: Boolean): Int = {
+ if (isDriver) {
+ conf.getInt(DRIVER_WAL_ROLLING_INTERVAL_CONF_KEY,
DEFAULT_ROLLING_INTERVAL_SECS)
+ } else {
+ conf.getInt(RECEIVER_WAL_ROLLING_INTERVAL_CONF_KEY,
DEFAULT_ROLLING_INTERVAL_SECS)
+ }
+ }
+
+ def getMaxFailures(conf: SparkConf, isDriver: Boolean): Int = {
+ if (isDriver) {
+ conf.getInt(DRIVER_WAL_MAX_FAILURES_CONF_KEY, DEFAULT_MAX_FAILURES)
+ } else {
+ conf.getInt(RECEIVER_WAL_MAX_FAILURES_CONF_KEY, DEFAULT_MAX_FAILURES)
+ }
+ }
+
+ /**
+ * Create a WriteAheadLog for the driver. If configured with custom WAL
class, it will try
+ * to create instance of that class, otherwise it will create the
default FileBasedWriteAheadLog.
+ */
+ def createLogForDriver(
+ sparkConf: SparkConf,
+ fileWalLogDirectory: String,
+ fileWalHadoopConf: Configuration
+ ): WriteAheadLog = {
+ createLog(true, sparkConf, fileWalLogDirectory, fileWalHadoopConf)
+ }
+
+ /**
+ * Create a WriteAheadLog for the receiver. If configured with custom
WAL class, it will try
+ * to create instance of that class, otherwise it will create the
default FileBasedWriteAheadLog.
+ */
+ def createLogForReceiver(
+ sparkConf: SparkConf,
+ fileWalLogDirectory: String,
+ fileWalHadoopConf: Configuration
+ ): WriteAheadLog = {
+ createLog(false, sparkConf, fileWalLogDirectory, fileWalHadoopConf)
+ }
+
+ /**
+ * Create a WriteAheadLog based on the value of the given config key.
The config key is used
+ * to get the class name from the SparkConf. If the class is configured,
it will try to
+ * create instance of that class by first trying `new
CustomWAL(sparkConf, logDir)` then trying
+ * `new CustomWAL(sparkConf)`. If either fails, it will fail. If no
class is configured, then
+ * it will create the default FileBasedWriteAheadLog.
+ */
+ private def createLog(
+ isDriver: Boolean,
+ sparkConf: SparkConf,
+ fileWalLogDirectory: String,
+ fileWalHadoopConf: Configuration
+ ): WriteAheadLog = {
+
+ val classNameOption = if (isDriver) {
+ sparkConf.getOption(DRIVER_WAL_CLASS_CONF_KEY)
+ } else {
+ sparkConf.getOption(RECEIVER_WAL_CLASS_CONF_KEY)
+ }
+ classNameOption.map { className =>
+ try {
+ instantiateClass(
+
Utils.classForName(className).asInstanceOf[Class[WriteAheadLog]], sparkConf)
+ } catch {
+ case NonFatal(e) =>
+ throw new SparkException(s"Could not create a write ahead log of
class $className", e)
+ }
+ }.getOrElse {
+ new FileBasedWriteAheadLog(sparkConf, fileWalLogDirectory,
fileWalHadoopConf,
+ getRollingIntervalSecs(sparkConf, isDriver),
getMaxFailures(sparkConf, isDriver))
+ }
+ }
+
+ /** Instantiate the class, either using single arg constructor or zero
arg constructor */
+ private def instantiateClass(cls: Class[WriteAheadLog], conf:
SparkConf): WriteAheadLog = {
--- End diff --
I think `Class[WriteAheadLog]` should be changed to `Class[_ <:
WriteAheadLog]`.
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