Github user harishreedharan commented on a diff in the pull request:
https://github.com/apache/spark/pull/2882#discussion_r19195251
--- Diff:
streaming/src/main/scala/org/apache/spark/streaming/util/WriteAheadLogReader.scala
---
@@ -0,0 +1,82 @@
+/*
+ * 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 java.io.{Closeable, EOFException}
+import java.nio.ByteBuffer
+
+import org.apache.hadoop.conf.Configuration
+import org.apache.spark.Logging
+
+/**
+ * A reader for reading write ahead log files written using
+ * [[org.apache.spark.streaming.util.WriteAheadLogWriter]]. This reads
+ * the records (bytebuffers) in the log file sequentially and return them
as an
+ * iterator of bytebuffers.
+ */
+private[streaming] class WriteAheadLogReader(path: String, conf:
Configuration)
+ extends Iterator[ByteBuffer] with Closeable with Logging {
+
+ private val instream = HdfsUtils.getInputStream(path, conf)
+ private var closed = false
+ private var nextItem: Option[ByteBuffer] = None
+
+ override def hasNext: Boolean = synchronized {
+ if (closed) {
+ return false
+ }
+
+ if (nextItem.isDefined) { // handle the case where hasNext is called
without calling next
+ true
+ } else {
+ try {
+ val length = instream.readInt()
+ val buffer = new Array[Byte](length)
+ instream.readFully(buffer)
+ nextItem = Some(ByteBuffer.wrap(buffer))
+ logTrace("Read next item " + nextItem.get)
+ true
+ } catch {
+ case e: EOFException =>
+ logDebug("Error reading next item, EOF reached", e)
+ close()
+ false
+ case e: Exception =>
+ logDebug("Error reading next item, EOF reached", e)
--- End diff --
Will fix in the next iter
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