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https://issues.apache.org/jira/browse/ZOOKEEPER-2789?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16022356#comment-16022356
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ASF GitHub Bot commented on ZOOKEEPER-2789:
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Github user asdf2014 commented on a diff in the pull request:
https://github.com/apache/zookeeper/pull/262#discussion_r118168282
--- Diff:
src/contrib/loggraph/src/java/org/apache/zookeeper/graph/JsonGenerator.java ---
@@ -121,8 +121,8 @@ public JsonGenerator(LogIterator iter) {
} else if ((m = newElectionP.matcher(e.getEntry())).find()) {
Iterator<Integer> iterator = servers.iterator();
long zxid = Long.valueOf(m.group(2));
- int count = (int)zxid;// & 0xFFFFFFFFL;
- int epoch = (int)Long.rotateRight(zxid, 32);// >> 32;
+ long count = zxid & 0xffffffffffL;
--- End diff --
Yeah, you are right!
> Reassign `ZXID` for solving 32bit overflow problem
> --------------------------------------------------
>
> Key: ZOOKEEPER-2789
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2789
> Project: ZooKeeper
> Issue Type: Bug
> Components: quorum
> Affects Versions: 3.5.3
> Reporter: Benedict Jin
> Fix For: 3.6.0
>
> Original Estimate: 168h
> Remaining Estimate: 168h
>
> If it is `1k/s` ops, then as long as $2^32 / (86400 * 1000) \approx 49.7$
> days ZXID will exhausted. But, if we reassign the `ZXID` into 16bit for
> `epoch` and 48bit for `counter`, then the problem will not occur until after
> $Math.min(2^16 / 365, 2^48 / (86400 * 1000 * 365)) \approx Math.min(179.6,
> 8925.5) = 179.6$ years.
> However, i thought the ZXID is `long` type, reading and writing the long type
> (and `double` type the same) in JVM, is divided into high 32bit and low 32bit
> part of the operation, and because the `ZXID` variable is not modified with
> `volatile` and is not boxed for the corresponding reference type (`Long` /
> `Double`), so it belongs to [non-atomic operation]
> (https://docs.oracle.com/javase/specs/jls/se8 /html/jls-17.html#jls-17.7).
> Thus, if the lower 32 bits of the upper 32 bits are divided into the entire
> 32 bits of the `long`, there may be a concurrent problem.
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