caiconghui opened a new issue #4630:
URL: https://github.com/apache/incubator-doris/issues/4630
**Describe the bug**
In our production environment, we find that removePriosIfNecessary encounter
exception like following:
java.util.ConcurrentModificationException: null
at java.util.HashMap$HashIterator.remove(HashMap.java:1507) ~[?:?]
at
com.google.common.collect.TransformedIterator.remove(TransformedIterator.java:53)
~[guava-15.0.jar:?]
at
org.apache.doris.clone.TabletChecker.removePriosIfNecessary(TabletChecker.java:356)
~[palo-fe.jar:?]
at
org.apache.doris.clone.TabletChecker.runAfterCatalogReady(TabletChecker.java:182)
~[palo-fe.jar:?]
at
org.apache.doris.common.util.MasterDaemon.runOneCycle(MasterDaemon.java:58)
~[palo-fe.jar:?]
at org.apache.doris.common.util.Daemon.run(Daemon.java:116)
[palo-fe.jar:?]
this is because iterator will be invalid when hashtable iterator(iter or
jter) invoke remove fuction more than once.
**To Reproduce**
I construct following case :
```
public class DemoTest {
public static void main(String[] args) {
com.google.common.collect.Table<Long, Long,
Set<TabletChecker.PrioPart>> copiedPrios = HashBasedTable.create();
copiedPrios.put(1L, 1L, new HashSet<>());
copiedPrios.put(1L, 2L, new HashSet<>());
copiedPrios.put(2L, 2L, new HashSet<>());
// List<Pair<Long, Long>> prios = Lists.newArrayList();
Iterator<Map.Entry<Long, Map<Long, Set<TabletChecker.PrioPart>>>>
iter = copiedPrios.rowMap().entrySet().iterator();
while (iter.hasNext()) {
Map.Entry<Long, Map<Long, Set<TabletChecker.PrioPart>>> dbEntry
= iter.next();
long dbId = dbEntry.getKey();
if (dbId % 2 == 0) {
iter.remove();
continue;
}
Iterator<Map.Entry<Long, Set<TabletChecker.PrioPart>>> jter =
dbEntry.getValue().entrySet().iterator();
while (jter.hasNext()) {
Map.Entry<Long, Set<TabletChecker.PrioPart>> tblEntry =
jter.next();
jter.remove();
// prios.add(Pair.create(dbId, tblEntry.getKey()));
}
}
// for (Pair<Long, Long> prio : prios) {
// copiedPrios.remove(prio.first, prio.second);
// }
System.out.println(copiedPrios.size());
}
}
```
Steps to reproduce the behavior:
run it and find that throw the following exception:
Exception in thread "main" java.util.ConcurrentModificationException
at java.util.HashMap$HashIterator.nextNode(HashMap.java:1429)
at java.util.HashMap$KeyIterator.next(HashMap.java:1453)
at
com.google.common.collect.TransformedIterator.next(TransformedIterator.java:48)
at org.apache.doris.DemoTest.main(DemoTest.java:23)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)
**Expected behavior**
A clear and concise description of what you expected to happen.
**Screenshots**
If applicable, add screenshots to help explain your problem.
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