GitHub user Randgalt opened a pull request:
https://github.com/apache/zookeeper/pull/377
[ZOOKEEPER-2901] TTL Nodes don't work with Server IDs > 127
There was a major oversight when TTL nodes were implemented. The session ID
generator for each server is seeded with the configured Server ID in the high
byte. TTL Nodes were using the highest bit to denote a TTL node when used in
the ephemeral owner. This meant that Server IDs > 127 that created ephemeral
nodes would have those nodes always considered TTL nodes (with the TTL being
essentially a random number).
This PR fixes the issue by disabling TTL Nodes by default. They must now be
enabled in zoo.cfg. When TTL Nodes are enabled, the max Server ID changes from
255 to 254. This allows the high byte of a session ID stored in the ephemeral
owner to use 0xFF to denote a TTL node.
About this change:
- The doc has been updated to note that TTL nodes are disabled by default
and must be enabled via config. Also, the docs explains that when TTL nodes are
enabled the max Server ID becomes 254
- The TTL implementation has been updated to use 0xFF in the high byte of
the ephemeralOwner to denote a TTL node. This decreases the max TTL by an
insignificant amount
- PrepRequestProcessor now throws `KeeperException.UnimplementedException`
when an attempt to create a TTL node is made but the server has not been
configured to enable TTL Nodes.
- QuorumPeer throws a `RuntimeException` if TTL Nodes are enabled but the
Server ID > 254
- Tests have been added to validate all of this
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/Randgalt/zookeeper ZOOKEEPER-2901
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/zookeeper/pull/377.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #377
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commit 21fa7716133e903c8d43c1003012837f980cb044
Author: randgalt <jor...@jordanzimmerman.com>
Date: 2017-09-22T22:10:30Z
There was a major oversight when TTL nodes were implemented. The session ID
generator for each server is seeded with the configured
Server ID in the high byte. TTL Nodes were using the highest bit to denote
a TTL node when used in the ephemeral owner. This meant
that Server IDs > 127 that created ephemeral nodes would have those nodes
always considered TTL nodes (with the TTL being essentially
a random number).
This PR fixes the issue by disabling TTL Nodes by default. They must now be
enabled in zoo.cfg. When TTL Nodes are enabled, the max
Server ID changes from 255 to 254. This allows the high byte of a session
ID stored in the ephemeral owner to use 0xFF to denote
a TTL node.
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