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From "Mithun Radhakrishnan (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HIVE-15491) Failures are masked/swallowed in GenericUDTFJSONTuple::process().
Date Wed, 21 Dec 2016 23:52:58 GMT

     [ https://issues.apache.org/jira/browse/HIVE-15491?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Mithun Radhakrishnan updated HIVE-15491:
----------------------------------------
    Affects Version/s: 2.1.1

> Failures are masked/swallowed in GenericUDTFJSONTuple::process().
> -----------------------------------------------------------------
>
>                 Key: HIVE-15491
>                 URL: https://issues.apache.org/jira/browse/HIVE-15491
>             Project: Hive
>          Issue Type: Bug
>    Affects Versions: 2.1.1
>            Reporter: Mithun Radhakrishnan
>
> I draw your attention to the following piece of code in {{GenericUDTFJSONTuple::process()}}:
> {code:java}
>   @Override
>   public void process(Object[] o) throws HiveException {
>   ...
>         for (int i = 0; i < numCols; ++i) {
>         if (retCols[i] == null) {
>           retCols[i] = cols[i]; // use the object pool rather than creating a new object
>         }
>         Object extractObject = ((Map<String, Object>)jsonObj).get(paths[i]);
>         if (extractObject instanceof Map || extractObject instanceof List) {
>           retCols[i].set(MAPPER.writeValueAsString(extractObject));
>         } else if (extractObject != null) {
>           retCols[i].set(extractObject.toString());
>         } else {
>           retCols[i] = null;
>         }
>       }
>       forward(retCols);
>       return;
>     } catch (Throwable e) {  <================= Yikes.
>       LOG.error("JSON parsing/evaluation exception" + e);
>       forward(nullCols);
>     }
>   }
> {code}
> The error-handling here seems suspect. Judging from the error message, the intention
here seems to be to catch JSON-specific errors arising from {{MAPPER.readValue()}} and {{MAPPER.writeValueAsString()}}.
By catching {{Throwable}}, this code masks the errors that arise from the call to {{forward(retCols)}}.
> I just ran into this in production. A user with a nearly exhausted HDFS quota attempted
to use {{json_tuple}} to extract fields from json strings in his data. The data turned out
to have large record counts and the query used over 25K mappers. Every task failed to create
a {{RecordWriter}}, thanks to the exhausted quota. But the thrown exception was swallowed
in the code above. {{process()}} ignored the failure for the record and proceeded to the next
one. Eventually, this resulted in DDoS-ing the name-node.
> I'll have a patch for this shortly.



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