Users can precisely control export parallelism.

Uses CombineFileInputFormat to run exports over a target number
of mappers independent of the number of input files.

From: Aaron Kimball <aaron@cloudera.com>

git-svn-id: https://svn.apache.org/repos/asf/incubator/sqoop/trunk@1149869 13f79535-47bb-0310-9956-ffa450edef68

src/java/org/apache/hadoop/sqoop/mapreduce/CombineShimRecordReader.java

@@ -0,0 +1,134 @@
+/**
+ * Licensed to Cloudera, Inc. under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  Cloudera, Inc. 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.hadoop.sqoop.mapreduce;
+
+import java.io.IOException;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.io.LongWritable;
+import org.apache.hadoop.mapreduce.InputSplit;
+import org.apache.hadoop.mapreduce.RecordReader;
+import org.apache.hadoop.mapreduce.TaskAttemptContext;
+import org.apache.hadoop.mapreduce.lib.input.CombineFileSplit;
+import org.apache.hadoop.mapreduce.lib.input.FileSplit;
+import org.apache.hadoop.mapreduce.lib.input.LineRecordReader;
+import org.apache.hadoop.mapreduce.lib.input.SequenceFileRecordReader;
+import org.apache.hadoop.util.ReflectionUtils;
+
+/**
+ * RecordReader that CombineFileRecordReader can instantiate, which itself
+ * translates a CombineFileSplit into a FileSplit.
+ */
+public class CombineShimRecordReader
+   extends RecordReader<LongWritable, Object> {
+
+  public static final Log LOG =
+     LogFactory.getLog(CombineShimRecordReader.class.getName());
+
+  private CombineFileSplit split;
+  private TaskAttemptContext context;
+  private int index;
+  private RecordReader<LongWritable, Object> rr;
+
+  /** 
+   * Constructor invoked by CombineFileRecordReader that identifies part of a
+   * CombineFileSplit to use.
+   */
+  public CombineShimRecordReader(CombineFileSplit split,
+      TaskAttemptContext context, Integer index)
+      throws IOException, InterruptedException {
+    this.index = index;
+    this.split = (CombineFileSplit) split;
+    this.context = context;
+
+    createChildReader();
+  }
+
+  @Override
+  public void initialize(InputSplit split, TaskAttemptContext context)
+      throws IOException, InterruptedException {
+    this.split = (CombineFileSplit) split;
+    this.context = context;
+
+    if (null == rr) {
+      createChildReader();
+    }
+
+    FileSplit fileSplit = new FileSplit(this.split.getPath(index),
+        this.split.getOffset(index), this.split.getLength(index),
+        this.split.getLocations());
+    this.rr.initialize(fileSplit, context);
+  }
+
+  @Override
+  public float getProgress() throws IOException, InterruptedException {
+    return rr.getProgress();
+  }
+
+  @Override
+  public void close() throws IOException {
+    if (null != rr) {
+      rr.close();
+      rr = null;
+    }
+  }
+
+  @Override
+  public LongWritable getCurrentKey()
+      throws IOException, InterruptedException {
+    return rr.getCurrentKey();
+  }
+
+  @Override
+  public Object getCurrentValue()
+      throws IOException, InterruptedException {
+    return rr.getCurrentValue();
+  }
+
+  @Override
+  public boolean nextKeyValue() throws IOException, InterruptedException {
+    return rr.nextKeyValue();
+  }
+
+  /**
+   * Actually instantiate the user's chosen RecordReader implementation.
+   */
+  @SuppressWarnings("unchecked")
+  private void createChildReader() throws IOException, InterruptedException {
+    LOG.debug("ChildSplit operates on: " + split.getPath(index));
+
+    Configuration conf = context.getConfiguration();
+
+    // Determine the file format we're reading.
+    Class rrClass;
+    if (ExportInputFormat.isSequenceFiles(conf, split.getPath(index))) {
+      rrClass = SequenceFileRecordReader.class;
+    } else {
+      rrClass = LineRecordReader.class;
+    }
+
+    // Create the appropriate record reader.
+    this.rr = (RecordReader<LongWritable, Object>)
+        ReflectionUtils.newInstance(rrClass, conf);
+  }
+}

src/java/org/apache/hadoop/sqoop/mapreduce/ExportInputFormat.java

@@ -0,0 +1,194 @@
+/**
+ * Licensed to Cloudera, Inc. under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  Cloudera, Inc. 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.hadoop.sqoop.mapreduce;
+
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.util.List;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.FileStatus;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.FSDataInputStream;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.io.LongWritable;
+import org.apache.hadoop.mapreduce.InputSplit;
+import org.apache.hadoop.mapreduce.JobContext;
+import org.apache.hadoop.mapreduce.RecordReader;
+import org.apache.hadoop.mapreduce.TaskAttemptContext;
+import org.apache.hadoop.mapreduce.lib.input.CombineFileInputFormat;
+import org.apache.hadoop.mapreduce.lib.input.CombineFileRecordReader;
+import org.apache.hadoop.mapreduce.lib.input.CombineFileSplit;
+
+/**
+ * InputFormat that generates a user-defined number of splits to inject data
+ * into the database.
+ */
+public class ExportInputFormat
+   extends CombineFileInputFormat<LongWritable, Object> {
+
+  public static final Log LOG =
+     LogFactory.getLog(ExportInputFormat.class.getName());
+
+  /** How many map tasks to use for export */
+  public static final String EXPORT_MAP_TASKS_KEY =
+      "sqoop.mapreduce.export.map.tasks";
+
+  public static final int DEFAULT_NUM_MAP_TASKS = 4;
+
+  public ExportInputFormat() {
+  }
+
+  /**
+   * @return true if p is a SequenceFile, or a directory containing
+   * SequenceFiles.
+   */
+  public static boolean isSequenceFiles(Configuration conf, Path p)
+      throws IOException {
+    FileSystem fs = p.getFileSystem(conf);
+
+    try {
+      FileStatus stat = fs.getFileStatus(p);
+
+      if (null == stat) {
+        // Couldn't get the item.
+        LOG.warn("Input path " + p + " does not exist");
+        return false;
+      }
+
+      if (stat.isDir()) {
+        FileStatus [] subitems = fs.listStatus(p);
+        if (subitems == null || subitems.length == 0) {
+          LOG.warn("Input path " + p + " contains no files");
+          return false; // empty dir.
+        }
+
+        // Pick a random child entry to examine instead.
+        stat = subitems[0];
+      }
+
+      if (null == stat) {
+        LOG.warn("null FileStatus object in isSequenceFiles(); assuming false.");
+        return false;
+      }
+
+      Path target = stat.getPath();
+      // Test target's header to see if it contains magic numbers indicating it's
+      // a SequenceFile.
+      byte [] header = new byte[3];
+      FSDataInputStream is = null;
+      try {
+        is = fs.open(target);
+        is.readFully(header);
+      } catch (IOException ioe) {
+        // Error reading header or EOF; assume not a SequenceFile.
+        LOG.warn("IOException checking SequenceFile header: " + ioe);
+        return false;
+      } finally {
+        try {
+          if (null != is) {
+            is.close();
+          }
+        } catch (IOException ioe) {
+          // ignore; closing.
+          LOG.warn("IOException closing input stream: " + ioe + "; ignoring.");
+        }
+      }
+
+      // Return true (isSequenceFile) iff the magic number sticks.
+      return header[0] == 'S' && header[1] == 'E' && header[2] == 'Q';
+    } catch (FileNotFoundException fnfe) {
+      LOG.warn("Input path " + p + " does not exist");
+      return false; // doesn't exist!
+    }
+  }
+
+  /**
+   * @return the number of bytes across all files in the job.
+   */
+  private long getJobSize(JobContext job) throws IOException {
+    List<FileStatus> stats = listStatus(job);
+    long count = 0;
+    for (FileStatus stat : stats) {
+      count += stat.getLen();
+    }
+
+    return count;
+  }
+
+  @Override
+  public List<InputSplit> getSplits(JobContext job) throws IOException {
+    // Set the max split size based on the number of map tasks we want.
+    long numTasks = getNumMapTasks(job);
+    long numFileBytes = getJobSize(job);
+    long maxSplitSize = numFileBytes / numTasks;
+
+    setMaxSplitSize(maxSplitSize);
+
+    LOG.debug("Target numMapTasks=" + numTasks);
+    LOG.debug("Total input bytes=" + numFileBytes);
+    LOG.debug("maxSplitSize=" + maxSplitSize);
+
+    List<InputSplit> splits =  super.getSplits(job);
+
+    if (LOG.isDebugEnabled()) {
+      LOG.debug("Generated splits:");
+      for (InputSplit split : splits) {
+        LOG.debug("  " + split);
+      }
+    }
+    return splits;
+  }
+
+  @Override
+  @SuppressWarnings("unchecked")
+  public RecordReader createRecordReader(
+      InputSplit split, TaskAttemptContext context) throws IOException {
+
+    CombineFileSplit combineSplit = (CombineFileSplit) split;
+
+    // Use CombineFileRecordReader since this can handle CombineFileSplits
+    // and instantiate another RecordReader in a loop; do this with the
+    // CombineShimRecordReader.
+    RecordReader rr = new CombineFileRecordReader(combineSplit, context,
+        CombineShimRecordReader.class);
+
+    return rr;
+  }
+
+  /**
+   * Allows the user to control the number of map tasks used for this
+   * export job.
+   */
+  public static void setNumMapTasks(JobContext job, int numTasks) {
+    job.getConfiguration().setInt(EXPORT_MAP_TASKS_KEY, numTasks);
+  }
+
+  /**
+   * @return the number of map tasks to use in this export job.
+   */
+  public static int getNumMapTasks(JobContext job) {
+    return job.getConfiguration().getInt(EXPORT_MAP_TASKS_KEY,
+        DEFAULT_NUM_MAP_TASKS);
+  }
+
+}

src/java/org/apache/hadoop/sqoop/mapreduce/ExportJob.java

@@ -63,70 +63,6 @@ public ExportJob(final ExportJobContext ctxt) {
     this.context = ctxt;
   }
 
-  /**
-   * @return true if p is a SequenceFile, or a directory containing
-   * SequenceFiles.
-   */
-  private boolean isSequenceFiles(Path p) throws IOException {
-    Configuration conf = context.getOptions().getConf();
-    FileSystem fs = p.getFileSystem(conf);
-
-    try {
-      FileStatus stat = fs.getFileStatus(p);
-
-      if (null == stat) {
-        // Couldn't get the item.
-        LOG.warn("Input path " + p + " does not exist");
-        return false;
-      }
-
-      if (stat.isDir()) {
-        FileStatus [] subitems = fs.listStatus(p);
-        if (subitems == null || subitems.length == 0) {
-          LOG.warn("Input path " + p + " contains no files");
-          return false; // empty dir.
-        }
-
-        // Pick a random child entry to examine instead.
-        stat = subitems[0];
-      }
-
-      if (null == stat) {
-        LOG.warn("null FileStatus object in isSequenceFiles(); assuming false.");
-        return false;
-      }
-
-      Path target = stat.getPath();
-      // Test target's header to see if it contains magic numbers indicating it's
-      // a SequenceFile.
-      byte [] header = new byte[3];
-      FSDataInputStream is = null;
-      try {
-        is = fs.open(target);
-        is.readFully(header);
-      } catch (IOException ioe) {
-        // Error reading header or EOF; assume not a SequenceFile.
-        LOG.warn("IOException checking SequenceFile header: " + ioe);
-        return false;
-      } finally {
-        try {
-          if (null != is) {
-            is.close();
-          }
-        } catch (IOException ioe) {
-          // ignore; closing.
-          LOG.warn("IOException closing input stream: " + ioe + "; ignoring.");
-        }
-      }
-
-      // Return true (isSequenceFile) iff the magic number sticks.
-      return header[0] == 'S' && header[1] == 'E' && header[2] == 'Q';
-    } catch (FileNotFoundException fnfe) {
-      LOG.warn("Input path " + p + " does not exist");
-      return false; // doesn't exist!
-    }
-  }
-
   /**
    * Run an export job to dump a table from HDFS to a database
    * @throws IOException if the export job encounters an IO error
@@ -161,16 +97,19 @@ public void runExport() throws ExportException, IOException {
       Path inputPath = new Path(context.getOptions().getExportDir());
       inputPath = inputPath.makeQualified(FileSystem.get(conf));
 
-      if (isSequenceFiles(inputPath)) {
-        job.setInputFormatClass(SequenceFileInputFormat.class);
+      boolean isSeqFiles = ExportInputFormat.isSequenceFiles(
+          context.getOptions().getConf(), inputPath);
+
+      if (isSeqFiles) {
         job.setMapperClass(SequenceFileExportMapper.class);
       } else {
-        job.setInputFormatClass(TextInputFormat.class);
         job.setMapperClass(TextExportMapper.class);
       }
 
+      job.setInputFormatClass(ExportInputFormat.class);
       FileInputFormat.addInputPath(job, inputPath);
       job.setNumReduceTasks(0);
+      ExportInputFormat.setNumMapTasks(job, options.getNumMappers());
 
       // Concurrent writes of the same records would be problematic.
       job.setMapSpeculativeExecution(false);

src/test/org/apache/hadoop/sqoop/TestExport.java

@@ -305,15 +305,44 @@ private void assertColMinAndMax(String colName, ColumnGenerator generator)
     assertColValForRowId(maxId, colName, expectedMax);
   }
 
+  private void multiFileTest(int numFiles, int recordsPerMap, int numMaps)
+      throws IOException, SQLException {
+
+    final int TOTAL_RECORDS = numFiles * recordsPerMap;
+
+    try {
+      LOG.info("Beginning test: numFiles=" + numFiles + "; recordsPerMap="
+          + recordsPerMap + "; numMaps=" + numMaps);
+
+      for (int i = 0; i < numFiles; i++) {
+        createTextFile(i, recordsPerMap, false);
+      }
+
+      createTable();
+      runExport(getArgv(true, "-m", "" + numMaps));
+      verifyExport(TOTAL_RECORDS);
+    } finally {
+      LOG.info("multi-file test complete");
+    }
+  }
+
   /** Export 10 rows, make sure they load in correctly */
   public void testTextExport() throws IOException, SQLException {
+    multiFileTest(1, 10, 1);
+  }
 
-    final int TOTAL_RECORDS = 10;
+  /** Make sure we can use CombineFileInputFormat to handle multiple
+   * files in a single mapper.
+   */
+  public void testMultiFilesOneMapper() throws IOException, SQLException {
+    multiFileTest(2, 10, 1);
+  }
 
-    createTextFile(0, TOTAL_RECORDS, false);
-    createTable();
-    runExport(getArgv(true));
-    verifyExport(TOTAL_RECORDS);
+  /** Make sure we can use CombineFileInputFormat to handle multiple
+   * files and multiple maps
+   */
+  public void testMultiFilesMultiMaps() throws IOException, SQLException {
+    multiFileTest(2, 10, 2);
   }
 
   /** Export 10 rows from gzipped text files. */

src/test/org/apache/hadoop/sqoop/testutil/ExportJobTestCase.java

@@ -66,6 +66,8 @@ protected String getTablePrefix() {
     args.add("\\t");
     args.add("--lines-terminated-by");
     args.add("\\n");
+    args.add("-m");
+    args.add("1");
 
 
     if (null != additionalArgv) {