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https://issues.apache.org/jira/browse/IOTDB-14?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jialin Qiao closed IOTDB-14.
----------------------------
Resolution: Cannot Reproduce
> Concurrent Error of HashMap in StatMonitor class
> ------------------------------------------------
>
> Key: IOTDB-14
> URL: https://issues.apache.org/jira/browse/IOTDB-14
> Project: Apache IoTDB
> Issue Type: Bug
> Reporter: xiangdong Huang
> Assignee: Rui Liu
> Priority: Major
> Labels: need-to-check
>
> When running IoTDB UT, I found an exception:
> [INFO] Running org.apache.iotdb.db.monitor.MonitorTest
> WARN [2019-01-28 23:50:28,816] [main]
> org.apache.iotdb.db.conf.IoTDBDescriptor:60 - Cannot find IOTDB_HOME or
> IOTDB_CONF environment variable when loading config file
> iotdb-engine.properties, use default configuration
> INFO [2019-01-28 23:50:28,822] [main]
> org.apache.iotdb.db.conf.directories.Directories:66 - folder
> data/data/settled in tsfileFolders doesn't exist, create it
> WARN [2019-01-28 23:50:28,823] [main]
> org.apache.iotdb.tsfile.common.conf.TSFileDescriptor:88 - Failed to find
> config file tsfile-format.properties at classpath, use default configuration
> INFO [2019-01-28 23:50:28,834] [main]
> org.apache.iotdb.db.auth.user.BasicUserManager:76 - Admin initialized
> INFO [2019-01-28 23:50:28,836] [main]
> org.apache.iotdb.db.auth.user.BasicUserManager:76 - Admin initialized
> INFO [2019-01-28 23:50:28,838] [main]
> org.apache.iotdb.db.auth.authorizer.BasicAuthorizer:62 - Initialization of
> Authorizer completes
> INFO [2019-01-28 23:50:28,840] [main]
> org.apache.iotdb.db.auth.user.BasicUserManager:76 - Admin initialized
> INFO [2019-01-28 23:50:28,841] [main]
> org.apache.iotdb.db.auth.authorizer.BasicAuthorizer:62 - Initialization of
> Authorizer completes
> INFO [2019-01-28 23:50:28,844] [main]
> org.apache.iotdb.db.engine.filenode.FileNodeManager:113 - data/system/info
> dir home doesn't exist, create it
> INFO [2019-01-28 23:50:29,866]
> [pool-1-IoTDB-StatMonitor-ServerServiceImpl-thread-1]
> org.apache.iotdb.db.engine.filenode.FileNodeProcessor:221 - The data
> directory of the filenode processor root.stats doesn't exist. Create new
> directory data/system/info/root.stats
> INFO [2019-01-28 23:50:29,876]
> [pool-1-IoTDB-StatMonitor-ServerServiceImpl-thread-1]
> org.apache.iotdb.db.engine.filenode.FileNodeProcessor:498 - Allocate folder
> data/data/settled for the new bufferwrite processor.
> ERROR [2019-01-28 23:50:33,855]
> [pool-1-IoTDB-StatMonitor-ServerServiceImpl-thread-1]
> org.apache.iotdb.db.monitor.StatMonitor$statBackLoop:376 - Error occurred in
> Stat Monitor thread
> java.util.ConcurrentModificationException: null
> at java.util.HashMap$HashIterator.nextNode(HashMap.java:1437)
> at java.util.HashMap$EntryIterator.next(HashMap.java:1471)
> at java.util.HashMap$EntryIterator.next(HashMap.java:1469)
> at
> org.apache.iotdb.db.monitor.StatMonitor.gatherStatistics(StatMonitor.java:264)
> at
> org.apache.iotdb.db.monitor.StatMonitor$statBackLoop.run(StatMonitor.java:372)
> at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
> at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
> at
> java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
> at
> java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
> at java.lang.Thread.run(Thread.java:748)
>
> It is because when you traverse a HashMap, the elements changed, I think.
>
> A strange thing is that org.apache.iotdb.db.monitor.MonitorTest passed... It
> is what we must fix, otherwise UT is meaningless.
>
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