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From Anthony Grasso <>
Subject Re: All time blocked in nodetool tpstats
Date Wed, 10 Apr 2019 23:36:21 GMT
Hi Abdul,

Usually we get no noticeable improvement at tuning concurrent_reads and
concurrent_writes above 128. I generally try to keep current_reads to no
higher than 64 and concurrent_writes to no higher than 128. In creasing the
values beyond that you might start running into issues where the kernel IO
scheduler and/or the disk become saturated. As Paul mentioned, it will
depend on the size of your nodes though.

If the client is timing out, it is likely that the node that is selected as
the coordinator for the read has a resource contention somewhere. The root
cause is usually due to a number of things going on though. As Paul
mentioned, one of the issues could be the query design. It is worth
investigating if a particular read query is timing out.

I would also inspect the Cassandra logs and garbage collection logs on the
node where you are seeing the timeouts. The things to look out for is high
garbage collection frequency, long garbage collection pauses, and high
tombstone read warnings.


On Thu, 11 Apr 2019 at 06:01, Abdul Patel <> wrote:

> Yes the queries are all select queries as they are more of read intensive
> app.
> Last night i rebooted cluster and today they are fine .(i know its
> temporary) as i still is all time blocked values.
> I am thinking of incresiing concurrent
> On Wednesday, April 10, 2019, Paul Chandler <> wrote:
>> Hi Abdul,
>> When I have seen dropped messages, I normally double check to ensure the
>> node not CPU bound.
>> If you have a high CPU idle value, then it is likely that tuning the
>> thread counts will help.
>> I normally start with concurrent_reads and concurrent_writes, so in your
>> case as reads are being dropped then increase concurrent_reads, I normally
>> change it to 96 to start with, but it will depend on size of your nodes.
>> Otherwise it might be badly designed queries, have you investigated which
>> queries are producing the client timeouts?
>> Regards
>> Paul Chandler
>> > On 9 Apr 2019, at 18:58, Abdul Patel <> wrote:
>> >
>> > Hi,
>> >
>> > My nodetool tpstats arw showing all time blocked high numbers a d also
>> read dropped messages as 400 .
>> > Client is expeirince high timeouts.
>> > Checked few online forums they recommend to increase,
>> native_transport_max_threads.
>> > As of jow its commented with 128 ..
>> > Is it adviabke to increase this and also can this fix timeout issue?
>> >
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