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