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https://issues.apache.org/jira/browse/MAPREDUCE-7133?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16597692#comment-16597692
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Oleksandr Shevchenko commented on MAPREDUCE-7133:
-------------------------------------------------
I found the issue MAPREDUCE-6440 which describe the same problem (did not see
this one before). In this ticket was proposed to rename the property in
TaskAttemptInfo but this is the incompatible change and this looks like the
workaround. I think we can to fix the main cause of the problem and save
backward compatibility.
> History Server task attempts REST API returns invalid data
> ----------------------------------------------------------
>
> Key: MAPREDUCE-7133
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-7133
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Reporter: Oleksandr Shevchenko
> Priority: Major
> Attachments: MAPREDUCE-7133.001.patch
>
>
> When we send a request to History Server with headers : Accept:
> application/json
> [https://nodename:19888/ws/v1/history/mapreduce/jobs/job_1535363926925_0040/tasks/task_1535363926925_0040_r_000003/attempts|https://192.168.121.199:19890/ws/v1/history/mapreduce/jobs/job_1535363926925_0040/tasks/task_1535363926925_0040_r_000003/attempts]
>
> we get the following JSON:
> {code:java}
> {
> "taskAttempts": {
> "taskAttempt": [{
> "type": "reduceTaskAttemptInfo",
> "startTime": 1535372984638,
> "finishTime": 1535372986149,
> "elapsedTime": 1511,
> "progress": 100.0,
> "id": "attempt_1535363926925_0040_r_000003_0",
> "rack": "/default-rack",
> "state": "SUCCEEDED",
> "status": "reduce > reduce",
> "nodeHttpAddress": "node2.cluster.com:8044",
> "diagnostics": "",
> "type": "REDUCE",
> "assignedContainerId": "container_e01_1535363926925_0040_01_000006",
> "shuffleFinishTime": 1535372986056,
> "mergeFinishTime": 1535372986075,
> "elapsedShuffleTime": 1418,
> "elapsedMergeTime": 19,
> "elapsedReduceTime": 74
> }]
> }
> }
> {code}
> As you can see "type" property has duplicates:
> "type": "reduceTaskAttemptInfo"
> "type": "REDUCE"
> It's lead to an error during parsing response body as JSON is not valid.
> When we use application/xml we get the following response:
> {code:java}
> <taskAttempts>
> <taskAttempt xmlns:xsi="[http://www.w3.org/2001/XMLSchema-instance]"
> xsi:type="reduceTaskAttemptInfo"><startTime>1535372984638</startTime><finishTime>1535372986149</finishTime><elapsedTime>1511</elapsedTime><progress>100.0</progress><id>attempt_1535363926925_0040_r_000003_0</id><rack>/default-rack</rack><state>SUCCEEDED</state><status>reduce
> >
> reduce</status><nodeHttpAddress>[node2.cluster.com:8044|http://node2.cluster.com:8044]</nodeHttpAddress><diagnostics/><type>REDUCE</type><assignedContainerId>container_e01_1535363926925_0040_01_000006</assignedContainerId><shuffleFinishTime>1535372986056</shuffleFinishTime><mergeFinishTime>1535372986075</mergeFinishTime><elapsedShuffleTime>1418</elapsedShuffleTime><elapsedMergeTime>19</elapsedMergeTime><elapsedReduceTime>74</elapsedReduceTime></taskAttempt>
> </taskAttempts>
> {code}
> Take a look at the following string:
> {code:java}
> <taskAttempt xmlns:xsi="[http://www.w3.org/2001/XMLSchema-instance]"
> xsi:type="reduceTaskAttemptInfo">
> {code}
> We got "xsi:type" attribute which incorectly marshall later to duplicated
> field if we use JSON format.
> It acceptable only to REDUCE task. For MAP task we get xml without "xsi:type"
> attribute.
> {code:java}
> <taskAttempts>
> <taskAttempt>
> <startTime>1535370756528</startTime>
> <finishTime>1535370760318</finishTime>
> <elapsedTime>3790</elapsedTime>
> <progress>100.0</progress>
> <id>attempt_1535363926925_0029_m_000001_0</id>
> <rack>/default-rack</rack>
> <state>SUCCEEDED</state>
> <status>map > sort</status>
> <nodeHttpAddress>[node2.cluster.com:8044|http://node2.cluster.com:8044]</nodeHttpAddress>
> <diagnostics/>
> <type>MAP</type>
> <assignedContainerId>container_e01_1535363926925_0029_01_000003</assignedContainerId>
> </taskAttempt>
> </taskAttempts>
> {code}
> This happens since we have two different hierarchical classes for MAP
> ->TaskAttemptInfo and REDUCE- > ReduceTaskAttemptInfo tasks.
> ReduceTaskAttemptInfo extends TaskAttemptInfo, later we marshal all tasks
> (map and reduce) by TaskAttemptsInfo.getTaskAttempt(). In this place, we do
> not have any information about ReduceTaskAttemptInfo type as we store all
> tasks in ArrayList<TaskAttemptInfo>.
> During marshaling we see that actual type of task ReduceTaskAttemptInfo
> instead of TaskAttemptsInfo and add meta information for this. That's why we
> get duplicated fields.
> Unfortunately we do not catch it before in TestHsWebServicesAttempts since we
> use
> org.codehaus.jettison.json.JSONObject library which overrides duplicated
> fields. Even when we use Postman to do request we get valid JSON. Only when
> we change represent type to Raw we can notice this issue. Also, we able to
> reproduce this bug by using "org.json:json" lib:
> Something like this:
> {code:java}
> BufferedReader inReader = new BufferedReader( new
> InputStreamReader(connection.getInputStream() ) );
> String inputLine;
> StringBuilder response = new StringBuilder();
> while ( (inputLine = inReader.readLine()) != null ) {
> response.append(inputLine);
> }
> inReader.close();
> JSONObject o = new JSONObject(response.toString());
> {code}
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