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https://issues.apache.org/jira/browse/ZOOKEEPER-1622?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13555212#comment-13555212
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Flavio Junqueira commented on ZOOKEEPER-1622:
---------------------------------------------
I haven't checked if the 40th bit will be set only by 2022, but otherwise the
change seems good to me, nice catch. I guess we just missed the opportunity of
having the equivalent of the Y2K bug for zookeeper in 2022. ;-)
> session ids will be negative in the year 2022
> ---------------------------------------------
>
> Key: ZOOKEEPER-1622
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1622
> Project: ZooKeeper
> Issue Type: Bug
> Reporter: Eric Newton
> Priority: Trivial
>
> Someone decided to use a large number for their myid file. This cause
> session ids to go negative, and our software (Apache Accumulo) did not handle
> this very well. While diagnosing the problem, I noticed this in SessionImpl:
> {noformat}
> public static long initializeNextSession(long id) {
> long nextSid = 0;
> nextSid = (System.currentTimeMillis() << 24) >> 8;
> nextSid = nextSid | (id <<56);
> return nextSid;
> }
> {noformat}
> When the 40th bit in System.currentTimeMillis() is a one, sign extension will
> fill the upper 8 bytes of nextSid, and id will not make the session id
> unique. I recommend changing the right shift to the logical shift:
> {noformat}
> public static long initializeNextSession(long id) {
> long nextSid = 0;
> nextSid = (System.currentTimeMillis() << 24) >>> 8;
> nextSid = nextSid | (id <<56);
> return nextSid;
> }
> {noformat}
> But, we have until the year 2022 before we have to worry about it.
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