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https://issues.apache.org/jira/browse/ZOOKEEPER-3365?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16871099#comment-16871099
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Hudson commented on ZOOKEEPER-3365:
-----------------------------------
SUCCESS: Integrated in Jenkins build Zookeeper-trunk-single-thread #417 (See
[https://builds.apache.org/job/Zookeeper-trunk-single-thread/417/])
ZOOKEEPER-3365: Use Concurrent HashMap with Counter in (nkalmar: rev
5627cd4a5a35b31b5b8143eec2a18940d914a7d4)
* (edit)
zookeeper-server/src/test/java/org/apache/zookeeper/test/ClientBase.java
* (edit)
zookeeper-server/src/main/java/org/apache/zookeeper/server/NettyServerCnxnFactory.java
* (edit)
zookeeper-server/src/test/java/org/apache/zookeeper/server/NettyServerCnxnTest.java
> Use Concurrent HashMap in NettyServerCnxnFactory
> -------------------------------------------------
>
> Key: ZOOKEEPER-3365
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-3365
> Project: ZooKeeper
> Issue Type: Improvement
> Components: server
> Affects Versions: 3.6.0
> Reporter: David Mollitor
> Assignee: David Mollitor
> Priority: Minor
> Labels: pull-request-available
> Fix For: 3.6.0
>
> Time Spent: 3.5h
> Remaining Estimate: 0h
>
> {code:java|title=NettyServerCnxnFactory.java}
> // Access to ipMap or to any Set contained in the map needs to be
> // protected with synchronized (ipMap) { ... }
> private final Map<InetAddress, Set<NettyServerCnxn>> ipMap = new
> HashMap<>();
> private void addCnxn(NettyServerCnxn cnxn) {
> cnxns.add(cnxn);
> synchronized (ipMap){
> InetAddress addr =
>
> ((InetSocketAddress)cnxn.getChannel().remoteAddress()).getAddress();
> Set<NettyServerCnxn> s = ipMap.get(addr);
> if (s == null) {
> s = new HashSet<>();
> ipMap.put(addr, s);
> }
> s.add(cnxn);
> }
> }
> {code}
> This can be done better (less code, less contention) with Java 8 Map API.
> Although, as I look at this, the only thing this is used for is a count of
> the number of connections from each address. Maybe this should just store a
> count instead of a collection.
> https://github.com/apache/zookeeper/blob/f69ad1b0fed88da3c1b67fd73031e7248c0564f7/zookeeper-server/src/main/java/org/apache/zookeeper/server/NettyServerCnxnFactory.java
> Also note that an exclusive lock is required with each interaction of the
> table. By moving to a {{ConcurrentHashMap}}:
> bq. Retrieval operations (including get) generally do not block, so may
> overlap with update operations (including put and remove).
> https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ConcurrentHashMap.html
> Removing this lock should improve ZK's performance for highly concurrent
> client workloads, especially since its Async Netty operations, unless of
> course there are other locks elsewhere.
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