[
https://issues.apache.org/jira/browse/BOOKKEEPER-760?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14009222#comment-14009222
]
Sijie Guo commented on BOOKKEEPER-760:
--------------------------------------
>> It depends on whether the session of the bookie has already expired, no?
yup. if the zk session was expired, the znode of that bookie will be removed
and the topology will be changed in clients, so the bookie will not be used for
new ensemble.
for current, a bookie will be shutdown immediately if its zookeeper session is
expired. but after BOOKKEEPER-537, a bookie will re-establish the zookeeper
session and re-registered itself when its previous session expired. so the
change is to prevent closing channels that a bookie isn't actually down but
whose session just expired, which cause unnecessary retries and ensemble
changes.
>> I don't understand how it affects latency.
it would trigger unnecessary ensemble change if a bookie isn't actually down
but just whose znode disappeared, so it would increase write latency.
for the read latency, it would cause client re-send the read to a different
bookie in same quorum, so the read latency will be increased due to retrying
the second bookie in same quorum.
>> I'm not sure what reordered means here. Do you mean to say rerouted or
>> resent?
Ah, the reorder would be in a different patch. I forgot to create the ticket
for it. The reorder means we read the entries based on the availability of
bookies (existence of znodes).
>> Do we even want to remove a bookkeeper client?
in theory, we might need to remove a bookie client if it is removed from the
cluster permanently. but since it is rare, it is ok that we don't remove it.
or, we could use a guava cache to maintain the pcbc clients, so we could evict
the idle clients to avoid increasing memory.
>> If we really don't need this part of the code, I'd rather remove it
>> altogether.
ah. I put it there with the comments so we don't add it back in future by
mistake.
> Don't close PCBC proactively if bookies disappeared from zookeeper znodes.
> --------------------------------------------------------------------------
>
> Key: BOOKKEEPER-760
> URL: https://issues.apache.org/jira/browse/BOOKKEEPER-760
> Project: Bookkeeper
> Issue Type: Improvement
> Components: bookkeeper-client
> Reporter: Sijie Guo
> Assignee: Sijie Guo
> Fix For: 4.3.0, 4.2.3
>
> Attachments: BOOKKEEPER-760.diff
>
>
> Don't close PCBC proactively if bookies disappeared from zookeeper znodes.
--
This message was sent by Atlassian JIRA
(v6.2#6252)
