Re: PendingTasks: What does it mean inside Cassandra?

[Girish Kumar]

Watching trends on these pools for increases in the pending tasks
column is an excellent indicator of the need to add additional capacity.

Additional capacity meaning add more writers and reader threads to handle
the requests  ?


On Tue, Oct 1, 2013 at 12:22 PM, Robert Coli rc...@eventbrite.com wrote:

 On Wed, Aug 28, 2013 at 5:47 AM, Girish Kumar girishkuma...@gmail.comwrote:

 When high number of Pending tasks are showing up what it means to
 cassandra? What are the reasons for high number pending tasks?  Does that
 mean Cassandra is overloaded ?


 It means that tasks have been queued to run inside of a Thread Pool, but
 are not currently running. A given task moves from Pending to Active state,
 and then Completed. Blocked is I attempted to move something from
 Pending to Active, but was unable to.

 http://www.datastax.com/docs/1.0/operations/monitoring
 
 Cassandra maintains distinct thread pools for different stages of
 execution. Each of these thread pools provide statistics on the number of
 tasks that are active, pending and completed. Watching trends on these
 pools for increases in the pending tasks column is an excellent indicator
 of the need to add additional capacity.
 

 =Rob

Re: PendingTasks: What does it mean inside Cassandra?

[Robert Coli]

On Wed, Aug 28, 2013 at 5:47 AM, Girish Kumar girishkuma...@gmail.comwrote:

 When high number of Pending tasks are showing up what it means to
 cassandra? What are the reasons for high number pending tasks?  Does that
 mean Cassandra is overloaded ?


It means that tasks have been queued to run inside of a Thread Pool, but
are not currently running. A given task moves from Pending to Active state,
and then Completed. Blocked is I attempted to move something from
Pending to Active, but was unable to.

http://www.datastax.com/docs/1.0/operations/monitoring

Cassandra maintains distinct thread pools for different stages of
execution. Each of these thread pools provide statistics on the number of
tasks that are active, pending and completed. Watching trends on these
pools for increases in the pending tasks column is an excellent indicator
of the need to add additional capacity.


=Rob

PendingTasks: What does it mean inside Cassandra?

[Girish Kumar]

Hi,

I have this problem of lots of pending tasks in Cassandra when I run
Cassandra with higher load. (Cassandra Stress threads set to 384).

The tpstat output shows high number Pending tasks  700.

When high number of Pending tasks are showing up what it means to
cassandra? What are the reasons for high number pending tasks?  Does that
mean Cassandra is overloaded ?

This question is in continuation with my earlier question on activecount
and pending task co-relation!!!

Thanks,
/BK