GitHub user DanBenediktson opened a pull request:
https://github.com/apache/zookeeper/pull/330
ZOOKEEPER-2471: ZK Java client should not count sleep time as connect time
ClientCnxnSocket uses a member variable "now" to track the current time,
but does not update it at all potentially-blocking times: in particular, it
does not update it after the random sleep introduced if an initial connect
attempt fails. This results in the random sleep time being counted towards
connect time, resulting in incorrect application of connection timeout
currently, and if ZOOKEEPER-2869 is taken, a very real possibility (we have
seen it in production) of wedging the Zookeeper client so that it can never
successfully reconnect, because its sleep time may grow beyond its connection
timeout, especially in scenarios where there is a big gap between negotiated
session timeout and client-requested session timeout.
Rather than fixing the bug by adding another "updateNow()" call, keeping
the brittle "updateNow()" implementation which led to the bug in the first
place, I have deleted updateNow() and replaced usage of that member variable
with actually getting the current system timestamp whenever the implementation
needs to know the current time.
Regarding unit testing, this is, IMO, too difficult to test without
introducing a lot of invasive changes to ClientCnxn.java, seeing as the only
effective change is that, on connection retry, the random sleep time is no
longer counted towards a time budget. I can throw a lot of mocks at this, like
ClientReconnectTest, but I'm still going to be stuck depending on the behavior
of that randomly-generated sleep time, which is going to be inherently
unreliable. If a fix is taken for ZOOKEEPER-2869, this should become much
easier to test, since I will then be able to inject a different backoff sleep
behavior, and since I'm planning to submit a pull request for that ticket as
well, so maybe as a compromise I can submit a test for this bug fix at that
time?
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/DanBenediktson/zookeeper ZOOKEEPER-2471
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/zookeeper/pull/330.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 #330
----
commit 60f38726e7f07b4bb970cc8fb089363ff48eb3df
Author: Dan Benediktson <dbenedikt...@twitter.com>
Date: 2017-08-09T16:41:42Z
ZOOKEEPER-2471: Zookeeper Java client should not count time spent sleeping
as time spent connecting
Rather than keep the brittle "updateNow()" implementation which led to the
bug and fixing the bug by
adding another "updateNow()" call, I have deleted updateNow() and replaced
usage of that member variable
with actually getting the current system timestamp.
This is, IMO, too difficult to test without introducing a lot of invasive
changes to ClientCnxn.java,
seeing as the only effective change is that, on connection retry, a random
sleep time is no longer
counted towards a time budget. If a fix is taken for ZOOKEEPER-2869, this
should become much easier to
test, and since I'm planning to submit a pull request for that ticket as
well, maybe as a compromise
I can submit a test for this patch at that time?
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