EdColeman commented on issue #637:
URL: https://github.com/apache/accumulo/issues/637#issuecomment-753216625
The advantage of using the uuid in the name vs. putting it in as a value is
that the node names and sequence can be determined by calling getChildren() and
then parsing the name. If the uuid was only in the value, then you would need
to call getChildren to get the node names, and then each client would need to
call getData to read the uuid on at least the node with the lowest sequence id.
If a client needed to know its place in the sequence, that client would need to
keep calling getData until if found its uuid (if existed at all).
To confirm that the sequence id is based on the parent node I manually
generated some nodes. The parent path is `/lock_test/myLocks/` and the
sequential, ephemeral nodes are named lock-9999`-,` `lock-1234-`, `lock-9876-`
(and in this order) - the 9999 node should have the lowest sequential id.
Looking in zookeeper, the nodes created are:
`[zk: localhost:2181(CONNECTED) 5] ls /lock_test/myLocks
[lock-1234-0000000001, lock-9876-0000000002, lock-9999-0000000000]
`
The nodes were created using:
` zk.create(
root + "/myLocks/lock-9999-",
null,
ZooDefs.Ids.OPEN_ACL_UNSAFE,
CreateMode.EPHEMERAL_SEQUENTIAL);
zk.create(
root + "/myLocks/lock-1234-",
null,
ZooDefs.Ids.OPEN_ACL_UNSAFE,
CreateMode.EPHEMERAL_SEQUENTIAL);
zk.create(
root + "/myLocks/lock-9876-",
null,
ZooDefs.Ids.OPEN_ACL_UNSAFE,
CreateMode.EPHEMERAL_SEQUENTIAL);
`
After the test exits, but with the zookeeper instance still running - the
sequential ids continue to increase, but the order remains as expected. On the
second run, the created nodes are:
`[zk: localhost:2181(CONNECTED) 7] ls /lock_test/myLocks
[lock-1234-0000000004, lock-9876-0000000005, lock-9999-0000000003]
`
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