cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Edward Capriolo <>
Subject Re: Meaning of values in tpstats
Date Sat, 10 Dec 2011 20:14:44 GMT
There was a recent patch that fixed an issue where counters were hitting
the same natural endpoint rather then being randomized across all of them.

On Saturday, December 10, 2011, Peter Schuller <>
>> Pool Name                    Active   Pending      Completed   Blocked
>> time blocked
>> ReadStage                        27      2166     3565927301         0
> In general, "active" refers to work that is being executed right now,
> "pending" refers to work that is waiting to be executed (go into
> "active"), and completed is the cumulative all-time (since node start)
> count of the number of tasks executed.
> With the slicing, I'm not sure off the top of my head. I'm sure
> someone else can chime in. For e.g. a multi-get, they end up as
> independent tasks.
> Typically having pending persistently above 0 for ReadStage or
> MutationStage, especially if more than a hand-ful, means that you are
> having a performance issue - either capacity problem or something
> else, as incoming requests will have to wait to be services. Typically
> the most common effect is that you are bottlenecking on I/O and
> ReadStage pending shoots through the roof.
> There are exceptions. If you e.g. submit a really large multi-get of
> 5000, that will naturally lead to a spike (and if all 5000 of them
> need to go down to disk, the spike will survive for a bit). If you are
> ONLY doing these queries, that's not a problem per se. But if you are
> also expecting other requests to have low latency, then you want to
> avoid it.
> In general, batching is good - but don't overdo it, especially for
> reads, and especially if you're going to disk for the workload.
> --
> / Peter Schuller (@scode,

View raw message