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https://issues.apache.org/jira/browse/APEXMALHAR-1965?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15250377#comment-15250377
]
ASF GitHub Bot commented on APEXMALHAR-1965:
--------------------------------------------
Github user davidyan74 commented on a diff in the pull request:
https://github.com/apache/incubator-apex-malhar/pull/242#discussion_r60456872
--- Diff:
library/src/main/java/org/apache/apex/malhar/lib/wal/FileSystemWAL.java ---
@@ -0,0 +1,598 @@
+/**
+ * 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.apex.malhar.lib.wal;
+
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.util.EnumSet;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.Map;
+import java.util.Set;
+import java.util.TreeMap;
+
+import javax.validation.constraints.Min;
+import javax.validation.constraints.NotNull;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import org.apache.apex.malhar.lib.utils.FileContextUtils;
+import org.apache.apex.malhar.lib.utils.IOUtils;
+import org.apache.apex.malhar.lib.utils.Serde;
+import org.apache.hadoop.fs.CreateFlag;
+import org.apache.hadoop.fs.FSDataOutputStream;
+import org.apache.hadoop.fs.FileContext;
+import org.apache.hadoop.fs.FileStatus;
+import org.apache.hadoop.fs.Options;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.fs.RemoteIterator;
+
+import com.google.common.base.Preconditions;
+
+import com.datatorrent.api.annotation.Stateless;
+
+public class FileSystemWAL<T> implements
WAL<FileSystemWAL.FileSystemWALReader, FileSystemWAL.FileSystemWALWriter>
+{
+ @NotNull
+ private Serde<T, byte[]> serde;
+
+ @NotNull
+ private String filePath;
+
+ //max length of the file
+ @Min(0)
+ private long maxLength;
+
+ @NotNull
+ private FileSystemWAL.FileSystemWALReader<T> fileSystemWALReader = new
FileSystemWALReader<>(this);
+
+ @NotNull
+ private FileSystemWAL.FileSystemWALWriter<T> fileSystemWALWriter = new
FileSystemWALWriter<>(this);
+
+ private long lastCheckpointedWindow = Stateless.WINDOW_ID;
+
+ @Override
+ public void setup()
+ {
+ try {
+ FileContext fileContext = FileContextUtils.getFileContext(filePath);
+ if (maxLength == 0) {
+ maxLength =
fileContext.getDefaultFileSystem().getServerDefaults().getBlockSize();
--- End diff --
@tweise But does it make sense to have a maxLength not a multiple of the FS
block size?
> Create a WAL in Malhar
> ----------------------
>
> Key: APEXMALHAR-1965
> URL: https://issues.apache.org/jira/browse/APEXMALHAR-1965
> Project: Apache Apex Malhar
> Issue Type: Task
> Reporter: Chandni Singh
> Assignee: Tushar Gosavi
>
> In Malhar we have an IdempotentStorageManager which we use like a Write Ahead
> Logger. There have been some other places where we have created a different
> flavor of Write Ahead Logger.
> We need to find overlap between all these flavors and create a common Write
> Ahead Logger for use in Apex core and Apex malhar.
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