{"action":"created","comment":{"url":"https://api.github.com/repos/caskdata/cdap/pulls/comments/38244346","id":38244346,"diff_hunk":"@@ -0,0 +1,66 @@\n+/*\n+ * Copyright © 2015 Cask Data, Inc.\n+ *\n+ * Licensed under the Apache License, Version 2.0 (the \"License\"); you may not\n+ * use this file except in compliance with the License. You may obtain a copy of\n+ * the License at\n+ *\n+ * http://www.apache.org/licenses/LICENSE-2.0\n+ *\n+ * Unless required by applicable law or agreed to in writing, software\n+ * distributed under the License is distributed on an \"AS IS\" BASIS, WITHOUT\n+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the\n+ * License for the specific language governing permissions and limitations under\n+ * the License.\n+ */\n+\n+package co.cask.cdap.mapreduce;\n+\n+import co.cask.cdap.api.ProgramLifecycle;\n+import com.google.common.io.Closeables;\n+import org.apache.hadoop.mapreduce.Mapper;\n+\n+import java.io.IOException;\n+\n+/**\n+ * Abstract Mapper class which provides functionality to a MapReduceTaskContext object, which allows writing to\n+ * multiple outputs.\n+ *\n+ * @param <KEYIN>    input key type\n+ * @param <VALUEIN>  input value type\n+ * @param <KEYOUT>   output key type\n+ * @param <VALUEOUT> output value type\n+ */\n+public abstract class AbstractMapper<KEYIN, VALUEIN, KEYOUT, VALUEOUT>\n+  extends Mapper<KEYIN, VALUEIN, KEYOUT, VALUEOUT>\n+  implements ProgramLifecycle<MapReduceTaskContext> {\n+\n+  private MapReduceTaskContext<KEYIN, VALUEIN, KEYOUT, VALUEOUT> context;\n+\n+  @Override\n+  public void initialize(MapReduceTaskContext context) throws Exception {\n+    this.context = context;\n+  }\n+\n+  @Override\n+  public void destroy() {\n+    Closeables.closeQuietly(context);\n+  }\n+\n+  /**\n+   * Called once for each key/value pair in the input split. Most applications\n+   * should override this, but the default is the identity function.\n+   */\n+  @SuppressWarnings(\"unchecked\")\n+  public void map(KEYIN key, VALUEIN value,\n+                  MapReduceTaskContext context) throws IOException, InterruptedException {\n+    context.write(key, value);","path":"cdap-api-hadoop/src/main/java/co/cask/cdap/mapreduce/AbstractMapper.java","position":54,"original_position":57,"commit_id":"017913cfb9a9cf988f6461f594894d0669208e0e","original_commit_id":"33473a609a421722b31e795562ab744fa7b46f32","user":{"login":"anew","id":483004,"avatar_url":"https://avatars.githubusercontent.com/u/483004?v=3","gravatar_id":"","url":"https://api.github.com/users/anew","html_url":"https://github.com/anew","followers_url":"https://api.github.com/users/anew/followers","following_url":"https://api.github.com/users/anew/following{/other_user}","gists_url":"https://api.github.com/users/anew/gists{/gist_id}","starred_url":"https://api.github.com/users/anew/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/anew/subscriptions","organizations_url":"https://api.github.com/users/anew/orgs","repos_url":"https://api.github.com/users/anew/repos","events_url":"https://api.github.com/users/anew/events{/privacy}","received_events_url":"https://api.github.com/users/anew/received_events","type":"User","site_admin":false},"body":"We are losing some type-safeness here. Mapper.Context is parameterized with KEYOUT and VALUEOUT, so you can only write correctly typed output. MapReduceTaskContext gives that up and type errors will only be found at runtime. I don't think that is good. ","created_at":"2015-08-28T21:06:35Z","updated_at":"2015-08-28T21:06:35Z","html_url":"https://github.com/caskdata/cdap/pull/3740#discussion_r38244346","pull_request_url":"https://api.github.com/repos/caskdata/cdap/pulls/3740","_links":{"self":{"href":"https://api.github.com/repos/caskdata/cdap/pulls/comments/38244346"},"html":{"href":"https://github.com/caskdata/cdap/pull/3740#discussion_r38244346"},"pull_request":{"href":"https://api.github.com/repos/caskdata/cdap/pulls/3740"}}},"pull_request":{"url":"https://api.github.com/repos/caskdata/cdap/pulls/3740","id":43667749,"html_url":"https://github.com/caskdata/cdap/pull/3740","diff_url":"https://github.com/caskdata/cdap/pull/3740.diff","patch_url":"https://github.com/caskdata/cdap/pull/3740.patch","issue_url":"https://api.github.com/repos/caskdata/cdap/issues/3740","number":3740,"state":"open","locked":false,"title":"Multiple Output Datasets","user":{"login":"anwar6953","id":2440977,"avatar_url":"https://avatars.githubusercontent.com/u/2440977?v=3","gravatar_id":"","url":"https://api.github.com/users/anwar6953","html_url":"https://github.com/anwar6953","followers_url":"https://api.github.com/users/anwar6953/followers","following_url":"https://api.github.com/users/anwar6953/following{/other_user}","gists_url":"https://api.github.com/users/anwar6953/gists{/gist_id}","starred_url":"https://api.github.com/users/anwar6953/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/anwar6953/subscriptions","organizations_url":"https://api.github.com/users/anwar6953/orgs","repos_url":"https://api.github.com/users/anwar6953/repos","events_url":"https://api.github.com/users/anwar6953/events{/privacy}","received_events_url":"https://api.github.com/users/anwar6953/received_events","type":"User","site_admin":false},"body":"This PR allows support for MR job to write to multiple output Datasets, according to the following design document: https://wiki.cask.co/display/CE/Multiple+Output+Datasets+of+MapReduce\r\n\r\nIn this PR, there are two test MapReduce jobs which utilize the new API; I am working on additional ones.\r\n\r\nhttps://issues.cask.co/browse/CDAP-2756\r\nhttp://builds.cask.co/browse/CDAP-DUT2564-3","created_at":"2015-08-28T20:18:24Z","updated_at":"2015-08-28T21:06:36Z","closed_at":null,"merged_at":null,"merge_commit_sha":"59616aec61e579346b3f90bcf30a65d9caac7517","assignee":null,"milestone":null,"commits_url":"https://api.github.com/repos/caskdata/cdap/pulls/3740/commits","review_comments_url":"https://api.github.com/repos/caskdata/cdap/pulls/3740/comments","review_comment_url":"https://api.github.com/repos/caskdata/cdap/pulls/comments{/number}","comments_url":"https://api.github.com/repos/caskdata/cdap/issues/3740/comments","statuses_url":"https://api.github.com/repos/caskdata/cdap/statuses/017913cfb9a9cf988f6461f594894d0669208e0e","head":{"label":"caskdata:feature/CDAP-2756-mapreduce-multiple-dataset-outputs","ref":"feature/CDAP-2756-mapreduce-multiple-dataset-outputs","sha":"017913cfb9a9cf988f6461f594894d0669208e0e","user":{"login":"caskdata","id":8123023,"avatar_url":"https://avatars.githubusercontent.com/u/8123023?v=3","gravatar_id":"","url":"https://api.github.com/users/caskdata","html_url":"https://github.com/caskdata","followers_url":"https://api.github.com/users/caskdata/followers","following_url":"https://api.github.com/users/caskdata/following{/other_user}","gists_url":"https://api.github.com/users/caskdata/gists{/gist_id}","starred_url":"https://api.github.com/users/caskdata/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/caskdata/subscriptions","organizations_url":"https://api.github.com/users/caskdata/orgs","repos_url":"https://api.github.com/users/caskdata/repos","events_url":"https://api.github.com/users/caskdata/events{/privacy}","received_events_url":"https://api.github.com/users/caskdata/received_events","type":"Organization","site_admin":false},"repo":{"id":22542759,"name":"cdap","full_name":"caskdata/cdap","owner":{"login":"caskdata","id":8123023,"avatar_url":"https://avatars.githubusercontent.com/u/8123023?v=3","gravatar_id":"","url":"https://api.github.com/users/caskdata","html_url":"https://github.com/caskdata","followers_url":"https://api.github.com/users/caskdata/followers","following_url":"https://api.github.com/users/caskdata/following{/other_user}","gists_url":"https://api.github.com/users/caskdata/gists{/gist_id}","starred_url":"https://api.github.com/users/caskdata/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/caskdata/subscriptions","organizations_url":"https://api.github.com/users/caskdata/orgs","repos_url":"https://api.github.com/users/caskdata/repos","events_url":"https://api.github.com/users/caskdata/events{/privacy}","received_events_url":"https://api.github.com/users/caskdata/received_events","type":"Organization","site_admin":false},"private":false,"html_url":"https://github.com/caskdata/cdap","description":"Cask 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