Github user pwendell commented on a diff in the pull request:
https://github.com/apache/spark/pull/5645#discussion_r29209731
--- Diff:
streaming/src/main/java/org/apache/spark/streaming/util/WriteAheadLog.java ---
@@ -0,0 +1,59 @@
+/*
+ * 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.nio.ByteBuffer;
+import java.util.Iterator;
+
+/**
+ * Interface representing a write ahead log (aka journal) that is used by
Spark Streaming to
+ * save the received data (by receivers) and associated metadata to a
reliable storage, so that
+ * they can be recovered after driver failures. See the Spark docs for
more information on how
+ * to plug in your own custom implementation of a write ahead log.
+ */
[email protected]
+public interface WriteAheadLog {
+ /**
+ * Write the record to the log and return the segment information that
is necessary to read
+ * back the written record. The time is used to the index the record,
such that it can be
+ * cleaned later. Note that the written data must be durable and
readable (using the
+ * segment info) by the time this function returns.
+ */
+ WriteAheadLogSegment write(ByteBuffer record, long time);
+
+ /**
+ * Read a written record based on the given segment information.
+ */
+ ByteBuffer read(WriteAheadLogSegment segment);
+
+ /**
+ * Read and return an iterator of all the records that have written and
not yet cleanup.
+ */
+ Iterator<ByteBuffer> readAll();
+
+ /**
+ * Cleanup all the records that are older than the given threshold time.
It can wait for
+ * the completion of the deletion.
+ */
+ void cleanup(long threshTime, boolean waitForCompletion);
--- End diff --
For some reason I feel like it should just be "clean" instead of "cleanup"
(as in "log cleaning"). This is totally subjective though so I think the
current one is OK to.
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