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https://issues.apache.org/jira/browse/CASSANDRA-11320?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15218590#comment-15218590
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Tyler Hobbs commented on CASSANDRA-11320:
-----------------------------------------
The patch looks good so far! Here are some review comments:
* The max backoff of 2^32 seconds is way too high. I feel like we should start
lower (maybe 10ms?) and set {{maxbackoffattempts}} to 12, for a max sleep of
~40 seconds.
* I'm also not sure if we should expose the three new config options to users.
They're advanced enough that I don't think anybody will realistically be able
to tune them well. As long as we pick decent defaults, I think they're okay
being internal only. (Plus, in a worst-case scenario, you can directly edit
the .py files.)
* In {{feed()}} (inside {{init_feeding_thread()}}), should we only be debug
printing the exception? It seems like we should at least be using printmsg(),
but I could be missing a good reason to keep it at the debug level. If there
is a good reason, add a code comment about it.
* I think {{filter_replica()}} can be renamed to
{{replica_is_not_overloaded()}} for more clarity.
* {{ConnectionWrapper.connections}} can be declared inside of the class as a
class-level attribute.
* Should we make {{maxinserterrors}} default to high non-negative value,
something like 1k? Right now, if your cluster goes down, it can take a _long_
time for COPY to error out the entire CSV file.
There's also a pretty minor issue: with {{--debug}} and a node that's slow to
respond, I sometimes see a few {{ImportError}}s like this:
{noformat}
Replicas too busy, given up
Traceback (most recent call last):
File "/home/thobbs/cassandra/bin/cqlsh.py", line 2618, in main
from tzlocal import get_localzone
ImportError: No module named tzlocal
{noformat}
> Improve backoff policy for cqlsh COPY FROM
> ------------------------------------------
>
> Key: CASSANDRA-11320
> URL: https://issues.apache.org/jira/browse/CASSANDRA-11320
> Project: Cassandra
> Issue Type: Improvement
> Components: Tools
> Reporter: Stefania
> Assignee: Stefania
> Labels: doc-impacting
> Fix For: 3.0.x, 3.x
>
>
> Currently we have an exponential back-off policy in COPY FROM that kicks in
> when timeouts are received. However there are two limitations:
> * it does not cover new requests and therefore we may not back-off
> sufficiently to give time to an overloaded server to recover
> * the pause is performed in the receiving thread and therefore we may not
> process server messages quickly enough
> There is a static throttling mechanism in rows per second from feeder to
> worker processes (the INGESTRATE) but the feeder has no idea of the load of
> each worker process. However it's easy to keep track of how many chunks a
> worker process has yet to read by introducing a bounded semaphore.
> The idea is to move the back-off pauses to the worker processes main thread
> so as to include all messages, new and retries, not just the retries that
> timed out. The worker process will not read new chunks during the back-off
> pauses, and the feeder process can then look at the number of pending chunks
> before sending new chunks to a worker process.
> [~aholmber], [~aweisberg] what do you think?
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