zhaojiandong commented on a change in pull request #6868: Fix deadlock in
DruidStatement & DruidConnection
URL: https://github.com/apache/incubator-druid/pull/6868#discussion_r248204737
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File path: sql/src/main/java/org/apache/druid/sql/avatica/DruidConnection.java
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@@ -63,7 +63,7 @@ public DruidConnection(final String connectionId, final int
maxStatements, final
this.connectionId = Preconditions.checkNotNull(connectionId);
this.maxStatements = maxStatements;
this.context = ImmutableMap.copyOf(context);
- this.statements = new HashMap<>();
+ this.statements = new ConcurrentHashMap<>();
Review comment:
> @zhaojiandong For clarity's sake, could you please change the type of the
field to ConcurrentMap, & a comment about why it's both `@GuardedBy` and
Concurrent?
>
> ```java
> // ConcurrentMap even though it is usually accessed synchronized, because
it's unsynchronized
> // in one case: the onClose function passed into DruidStatements contained
by the map. This is
> // done to avoid deadlocks; see
https://github.com/apache/incubator-druid/issues/6867.
> @GuardedBy("statements")
> private final ConcurrentMap<Integer, DruidStatement> statements;
> ```
How about use another sync flag: connectionLock, and statements 's type is
ConcurrentMap.
In this way GuardedBy check will passed. @gianm
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