[GitHub] [hbase] catalin-luca commented on a change in pull request #2002: HBASE-24541 Add support to run LoadIncrementalHFiles in a distributed manner

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catalin-luca commented on a change in pull request #2002:
URL: https://github.com/apache/hbase/pull/2002#discussion_r451051217



##########
File path: hbase-server/src/main/java/org/apache/hadoop/hbase/mapreduce/LoadIncrementalHFilesJob.java
##########
@@ -0,0 +1,348 @@
+/**
+ * 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.hadoop.hbase.mapreduce;
+
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.collect.Iterators;
+import com.google.common.collect.Lists;
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.conf.Configured;
+import org.apache.hadoop.fs.FileStatus;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.hbase.HBaseConfiguration;
+import org.apache.hadoop.hbase.HColumnDescriptor;
+import org.apache.hadoop.hbase.TableName;
+import org.apache.hadoop.hbase.client.Connection;
+import org.apache.hadoop.hbase.client.ConnectionFactory;
+import org.apache.hadoop.hbase.client.RegionLocator;
+import org.apache.hadoop.hbase.client.Table;
+import org.apache.hadoop.hbase.io.HFileLink;
+import org.apache.hadoop.hbase.regionserver.StoreFileInfo;
+import org.apache.hadoop.hbase.util.Bytes;
+import org.apache.hadoop.io.ArrayWritable;
+import org.apache.hadoop.io.NullWritable;
+import org.apache.hadoop.io.Text;
+import org.apache.hadoop.io.Writable;
+import org.apache.hadoop.mapreduce.*;
+import org.apache.hadoop.mapreduce.lib.output.NullOutputFormat;
+import org.apache.hadoop.util.Tool;
+import org.apache.hadoop.util.ToolRunner;
+
+import java.io.DataInput;
+import java.io.DataOutput;
+import java.io.IOException;
+import java.util.*;
+
+public class LoadIncrementalHFilesJob extends Configured implements Tool {
+
+  private static final Log LOG = LogFactory.getLog(LoadIncrementalHFilesJob.class);
+
+  public static final String ROOT_DIR = "loadincrementalhfilesjob.root.dir";
+  public static final String TABLE_NAME = "loadincrementalhfilesjob.table.name";
+  public static final String MAX_MAP_TASK = "loadincrementalhfilesjob.max.map.tasks";
+  public static final String DEPTH = "loadincrementalhfilesjob.depth";
+
+  @Override public int run(String[] args) throws Exception {
+    Configuration configuration = HBaseConfiguration.create(getConf());
+
+    return run(args[0], args[1], configuration);
+  }
+
+  @VisibleForTesting public int run(String rootPath, String table, Configuration configuration)
+      throws Exception {
+    Path basePath = new Path(rootPath);
+    configuration.set(TABLE_NAME, table);
+    configuration.set(ROOT_DIR, basePath.toString());
+
+    if (!bulkload(basePath, table, configuration)) {
+      return 1;
+    }
+
+    return 0;
+  }
+
+  private boolean bulkload(Path rootDir, String table, Configuration configuration)
+      throws Exception {
+    Configuration jobConfiguration = new Configuration(configuration);
+
+    applyNonOverridableOptions(jobConfiguration);
+
+    Job job = Job.getInstance(jobConfiguration, "Bulkload-" + table + "-" + rootDir.toString());
+
+    TableMapReduceUtil.addDependencyJars(job);
+
+    job.setJarByClass(LoadIncrementalHFilesJob.class);
+
+    job.setInputFormatClass(BulkLoadInputFormat.class);
+    job.setOutputFormatClass(NullOutputFormat.class);
+
+    job.setMapperClass(BulkoadMapper.class);
+    job.setMapOutputKeyClass(NullWritable.class);
+    job.setMapOutputValueClass(NullWritable.class);
+
+    job.setNumReduceTasks(0);
+
+    return job.waitForCompletion(true);
+  }
+
+  private static void applyNonOverridableOptions(Configuration configuration) {

Review comment:
       These settings basically account for the fact that the map task is not using a hadoop `OutputFormat` to write its output: 
    - Task timeout is disabled because it is based on the map/reduce idea of progress (which means either writing to the hadoop `Mapper.Context` or the `OutputFormat`). The `BulkloadMapper` code does neither, so it would inevitably timeout.
    - Speculative execution and task retry are disabled because they would fail anyway. A speculated task would attempt to bulkload the same set of files as the original resulting in a failure. A retried task would potentially attempt to bulkload files that were already bulk loaded by the original task.
   
   I don't think an `OutputFormat` can be implemented because there is no way to implement the `OutputCommitter` contract reliably without changes to the region server side. 




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