[jira] [Commented] (IOTDB-735) Concurrent error for MNode when creating time series automatically

["Jialin Qiao (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/IOTDB-735?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17123771#comment-17123771 ] 

Jialin Qiao commented on IOTDB-735:
-----------------------------------

[https://github.com/apache/incubator-iotdb/pull/1306]

> Concurrent error for MNode when creating time series automatically
> ------------------------------------------------------------------
>
>                 Key: IOTDB-735
>                 URL: https://issues.apache.org/jira/browse/IOTDB-735
>             Project: Apache IoTDB
>          Issue Type: Bug
>          Components: Core/Engine
>    Affects Versions: 0.10.0-SNAPSHOT, 0.9.3
>            Reporter: Xiangdong Huang
>            Priority: Major
>              Labels: pull-request-available
>
> When multiply users write time series data concurrently and IoTDB enables auto_create_timeseries, sometimes NullpointException may be thrown from PlanExecutor.
>  
> The NullPointer exception is thrown from `LeafMNode measurementNode = (LeafMNode) node.getChild(measurement);`. 
>  
> {code:java}
> // code placeholder
> @Override
> public void insert(InsertPlan insertPlan) throws QueryProcessException {
>   MNode node = null;
>   try {
>     String[] measurementList = insertPlan.getMeasurements();
>     String deviceId = insertPlan.getDeviceId();
>     node = mManager.getDeviceNodeWithAutoCreateAndReadLock(deviceId);
>     MeasurementSchema[] schemas = new MeasurementSchema[measurementList.length];
>     for (int i = 0; i < measurementList.length; i++) {
>       String measurement = measurementList[i];
>       if (!node.hasChild(measurement)) {
>         if (!IoTDBDescriptor.getInstance().getConfig().isAutoCreateSchemaEnabled()) {
>           throw new PathNotExistException(deviceId + PATH_SEPARATOR + measurement);
>         }
>         TSDataType dataType = TypeInferenceUtils
>             .getPredictedDataType(insertPlan.getValues()[i], insertPlan.isInferType());
>         Path path = new Path(deviceId, measurement);
>         internalCreateTimeseries(path.toString(), dataType);
>       }
>       LeafMNode measurementNode = (LeafMNode) node.getChild(measurement);
>       schemas[i] = measurementNode.getSchema();
>       // reset measurement to common name instead of alias
>       measurementList[i] = measurementNode.getName();
>       if(!insertPlan.isInferType()) {
>         checkType(insertPlan, i, measurementNode.getSchema().getType());
>       }
>     }
>     insertPlan.setMeasurements(measurementList);
>     insertPlan.setSchemasAndTransferType(schemas);
>     StorageEngine.getInstance().insert(insertPlan);
>   } catch (StorageEngineException | MetadataException e) {
>     throw new QueryProcessException(e);
>   } finally {
>     if (node != null) {
>       ((InternalMNode) node).readUnlock();
>     }
>   }
> }
> {code}
> The reason is, this method operates MNode instance directly without mtree.lock. Then, when `node.getChild()` is called, someone may call `node.addChild()` and the Concurrent error may lead the `node.getChild()` returns null.
>  
> So, be careful when you directly operate a MNode instance.
>  
>  
>  
>  
>  



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