My methodology was as follows. Since the true parallelism of a machine is the the no. of cores, I set the workers equal to no. of cores. (5 in my case). That being said, since we have 32 GB per box, we usually leave 50% off leaving us 16 GB spread across 5 machines. Hence we set the worker heap at 3g.

This was before Javiers and Michaels suggestion of keeping one JVM per node...

Ours is a single topology running on the boxes and hence I would be changing it to one JVM (worker) per box and rerunning.


On Mon, Oct 5, 2015 at 9:18 AM, anshu shukla <> wrote:
Sorry for reposting !! Any suggestions Please . 

Just one query How we can map -
1-no of workers to number of  cores 
2-no of slots on one machine to number of cores over that machine

On Mon, Oct 5, 2015 at 7:32 PM, John Yost <> wrote:
Hi Javier,

Gotcha, I am seeing the same thing, and I see a ton of worker restarts as well.



On Mon, Oct 5, 2015 at 9:01 AM, Javier Gonzalez <> wrote:

I don't have numbers, but I did see a very noticeable degradation of throughput and latency when using multiple workers per node with the same topology.

On Oct 5, 2015 7:25 AM, "John Yost" <> wrote:
Hi Everyone,

I am curious--are there any benchmark numbers that demonstrate how much better one worker per node is?  The reason I ask is that I may need to double up the workers on my cluster and I was wondering how much of a throughput hit I may take from having two workers per node.

Any info would be very much appreciated--thanks! :)


On Sat, Oct 3, 2015 at 9:04 AM, Javier Gonzalez <> wrote:
I would suggest sticking with a single worker per machine. It makes memory allocation easier and it makes inter-component communication much more efficient. Configure the executors with your parallelism hints to take advantage of all your availabe CPU cores.


On Sat, Oct 3, 2015 at 12:10 AM, Kashyap Mhaisekar <> wrote:

I was trying to come up with an approach to evaluate the parallelism needed for a topology.

Assuming I have 5 machines with 8 cores and 32 gb. And my topology has one spout and 5 bolts.

1. Define one worker port per CPU to start off. (= 8 workers per machine ie 40 workers over all)
2. Each worker spawns one executor per component per worker, it translates to 6 executors per worker which is 40x6= 240 executors.
3. Of this, if the bolt logic is CPU intensive, then leave parallelism hint  at 40 (total workers), else increase parallelism hint beyond 40 till you hit a number beyond which there is no more visible performance.

Does this look right?


Javier González Nicolini

Thanks & Regards,
Anshu Shukla