[GitHub] jiazhai commented on a change in pull request #43: DLFS - A filesystem built on replicated logs

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jiazhai commented on a change in pull request #43: DLFS - A filesystem built on replicated logs
URL: https://github.com/apache/distributedlog/pull/43#discussion_r146567445
 
 

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 File path: distributedlog-contribs/distributedlog-hdfs/src/main/java/com/twitter/distributedlog/fs/DistributedLogFileSystem.java
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+/**
+ * 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 com.twitter.distributedlog.fs;
+
+import com.google.common.base.Optional;
+import com.twitter.distributedlog.AppendOnlyStreamReader;
+import com.twitter.distributedlog.AppendOnlyStreamWriter;
+import com.twitter.distributedlog.DistributedLogConfiguration;
+import com.twitter.distributedlog.DistributedLogConstants;
+import com.twitter.distributedlog.DistributedLogManager;
+import com.twitter.distributedlog.config.DynamicDistributedLogConfiguration;
+import com.twitter.distributedlog.exceptions.LogEmptyException;
+import com.twitter.distributedlog.exceptions.LogNotFoundException;
+import com.twitter.distributedlog.namespace.DistributedLogNamespace;
+import com.twitter.distributedlog.namespace.DistributedLogNamespaceBuilder;
+import org.apache.commons.configuration.ConfigurationException;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.BufferedFSInputStream;
+import org.apache.hadoop.fs.FSDataInputStream;
+import org.apache.hadoop.fs.FSDataOutputStream;
+import org.apache.hadoop.fs.FileStatus;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.fs.permission.FsPermission;
+import org.apache.hadoop.util.Progressable;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.BufferedOutputStream;
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.net.InetAddress;
+import java.net.URI;
+
+/**
+ * A FileSystem Implementation powered by replicated logs
+ */
+public class DistributedLogFileSystem extends FileSystem {
+
+    private final Logger logger = LoggerFactory.getLogger(DistributedLogFileSystem.class);
+
+    //
+    // Settings
+    //
+
+    public static final String DLFS_CONF_FILE = "dlfs.configuration.file";
+
+
+    private URI rootUri;
+    private DistributedLogNamespace namespace;
+    private final DistributedLogConfiguration dlConf;
+    private Path workingDir;
+
+    public DistributedLogFileSystem() {
+        this.dlConf = new DistributedLogConfiguration();
+    }
+
+    @Override
+    public URI getUri() {
+        return rootUri;
+    }
+
+    //
+    // Initialization
+    //
+
+    @Override
+    public void initialize(URI name, Configuration conf) throws IOException {
+        super.initialize(name, conf);
+        setConf(conf);
+
+        // initialize
+
+        this.rootUri = name;
+        // load the configuration
+        String dlConfLocation = conf.get(DLFS_CONF_FILE);
+        if (null != dlConfLocation) {
+            try {
+                this.dlConf.loadConf(new File(dlConfLocation).toURI().toURL());
+                logger.info("Loaded the distributedlog configuration from {}", dlConfLocation);
+            } catch (ConfigurationException e) {
+                logger.error("Failed to load the distributedlog configuration from " + dlConfLocation, e);
+                throw new IOException("Failed to load distributedlog configuration from " + dlConfLocation);
+            }
+        }
+        // initialize the namespace
+        this.namespace = DistributedLogNamespaceBuilder.newBuilder()
+                .clientId("dlfs-client-" + InetAddress.getLocalHost().getHostName())
+                .conf(dlConf)
+                .regionId(DistributedLogConstants.LOCAL_REGION_ID)
+                .uri(name)
+                .build();
+        logger.info("Initialized the filesystem at {}", name);
+    }
+
+    @Override
+    public void close() throws IOException {
+        // clean up the resource
+        namespace.close();
+        super.close();
+    }
+
+    //
+    // Util Functions
+    //
+
+    private Path makeAbsolute(Path f) {
+        if (f.isAbsolute()) {
+            return f;
+        } else {
+            return new Path(workingDir, f);
+        }
+    }
+
+    private String getStreamName(Path absolutePath) {
+        return absolutePath.toUri().getPath().substring(1);
+    }
+
+    //
+    // Home & Working Directory
+    //
+
+    @Override
+    public Path getHomeDirectory() {
+        return this.makeQualified(new Path(System.getProperty("user.home")));
+    }
+
+    protected Path getInitialWorkingDirectory() {
+        return this.makeQualified(new Path(System.getProperty("user.dir")));
+    }
+
+    @Override
+    public void setWorkingDirectory(Path path) {
+        workingDir = makeAbsolute(path);
+        checkPath(workingDir);
+    }
+
+    @Override
+    public Path getWorkingDirectory() {
+        return workingDir;
+    }
+
+
+    @Override
+    public FSDataInputStream open(Path path, int bufferSize)
+            throws IOException {
+        Path absolutePath = makeAbsolute(path);
+        DistributedLogManager dlm = namespace.openLog(getStreamName(absolutePath));
+        AppendOnlyStreamReader reader;
+        try {
+            reader = dlm.getAppendOnlyStreamReader();
+        } catch (LogNotFoundException lnfe) {
+            throw new FileNotFoundException(path.toString());
+        } catch (LogEmptyException lee) {
+            throw new FileNotFoundException(path.toString());
+        }
+        return new FSDataInputStream(
+                new BufferedFSInputStream(
+                        new DistributedLogInputStream(dlm, reader),
+                        bufferSize));
+    }
+
+    @Override
+    public FSDataOutputStream create(Path path,
+                                     FsPermission fsPermission,
+                                     boolean overwrite,
+                                     int bufferSize,
+                                     short replication,
+                                     long blockSize,
+                                     Progressable progressable) throws IOException {
+
+        // TODO: support overwrite, support permission
 
 Review comment:
   Shall we open a github issue for this?

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