[GitHub] [bookkeeper] eolivelli commented on a change in pull request #2742: [WIP] Abstract the FileChannel in the JournalChannel

[GitBox <gi...@apache.org>]

eolivelli commented on a change in pull request #2742:
URL: https://github.com/apache/bookkeeper/pull/2742#discussion_r654883392



##########
File path: bookkeeper-server/src/main/java/org/apache/bookkeeper/bookie/DefaultFileChannelProvider.java
##########
@@ -0,0 +1,64 @@
+/**
+ * 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.bookkeeper.bookie;
+
+import org.apache.bookkeeper.conf.ServerConfiguration;
+
+import java.io.File;
+import java.io.FileDescriptor;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.io.RandomAccessFile;
+import java.nio.channels.FileChannel;
+
+public class DefaultFileChannelProvider implements FileChannelProvider{
+    @Override
+    public BookieFileChannel open(File file, ServerConfiguration configuration) throws IOException {
+        return new DefaultFileChannel(file, configuration);
+    }
+
+    static class DefaultFileChannel implements BookieFileChannel {
+        private final File file;
+        private static RandomAccessFile randomAccessFile;
+        private final ServerConfiguration configuration;
+
+        DefaultFileChannel(File file, ServerConfiguration serverConfiguration) throws IOException {
+            this.file = file;
+            this.configuration = serverConfiguration;
+        }
+
+        @Override
+        public FileChannel getFileChannel() throws FileNotFoundException {
+            if (randomAccessFile == null) {

Review comment:
       There isn't any kind of concurrency control here.
   
   Is this intended?
   IMHO it is better to add at least 'synchonized'

##########
File path: bookkeeper-server/src/main/java/org/apache/bookkeeper/bookie/JournalChannel.java
##########
@@ -143,27 +146,39 @@
     private JournalChannel(File journalDirectory, long logId,
                            long preAllocSize, int writeBufferSize, int journalAlignSize,
                            long position, boolean fRemoveFromPageCache,
-                           int formatVersionToWrite, Journal.BufferedChannelBuilder bcBuilder) throws IOException {
+                           int formatVersionToWrite, Journal.BufferedChannelBuilder bcBuilder,
+                           ServerConfiguration configuration) throws IOException {
         this.journalAlignSize = journalAlignSize;
         this.zeros = ByteBuffer.allocate(journalAlignSize);
         this.preAllocSize = preAllocSize - preAllocSize % journalAlignSize;
         this.fRemoveFromPageCache = fRemoveFromPageCache;
+        this.configuration = configuration;
+
         File fn = new File(journalDirectory, Long.toHexString(logId) + ".txn");
+        FileChannelProvider provider;
+        // Create the file channel provider with given configuration. Fallback to use default FileChannel if
+        // load failed.
+        try {
+            provider = FileChannelProvider.newProvider(configuration.getJournalChannelProvider());
+        } catch (IOException e) {
+            LOG.warn("Failed to load journal channel provider '{}', fallback to the default JournalChannel", configuration.getJournalChannelProvider(), e);
+            provider = new DefaultFileChannelProvider();

Review comment:
       We should fail here because in this case the Bookie won't work as expected by who configured it
   And the impact on the system will be significant 




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