On Apr 17, 2009, at 4:12 PM, mwcotton wrote:
> I see the ability to have multiple zenhub workers, whats the school  
> of thought on when to add a worker? Is there a log I can look at? Is  
> it a cpu or memory issue? Seems like the more the better, but in the  
> computer world that doesnt always hold true.

The default configuration is to not use workers at all. What you  
should be on the lookout for in this configuration for that would tip  
you off to enable workers would be regular "Timeout connecting to  
zenhub: is it running?" messages when you attempt to remodel devices  
or in other areas.

So now.. now many workers? There's no right answer for every possible  
scenario, but there are some good rules of thumb. The first would be  
that you never want to exceed the total number of CPU cores minus one.  
So on a 4 core box, you wouldn't want more than 3 workers. This is to  
keep the web interface responsive.

Maybe more importantly, you could start by enabling 2 workers. Then  
you can keep an eye on the size of your zenhub queue. This isn't one  
of the standard collector metrics right now, but you can enabled it by  
following the following steps.

1. Go to http://yourzenoss:8080/zport/dmd/Monitors/perfConfig
2. Click into the PerformanceConf template
3. Add a new data source. The name is zenhub and the type is Built-In
4. Add a data point to this zenhub data source called workListLength
5. Add a new graph to the PerformanceConf template
6. Add the zenhub_workListLength to this graph.

Now when you click on the Performance tab of your collector you will  
be able to see what the size of the zenhub queue has been over time.  
You should never see it go over 50, and it should stay below 10 the  
vast majority of the time. If this is not the case, you can increase  
the number of zenhub workers up to the total cores minus one ceiling  
mentioned above.

If you get to this point and your zenhub queue is still too high, your  
server likely needs more horsepower.
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