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Re: Scaling In OpenShift -Queries

On 3/27/13 10:21 PM, s madathilthattantav accenture com wrote:


Hi All


Have some queries regarding Auto Scaling feature with  HAProxy.Any pointer will be really helpful and appreciated.



1.       In the HAProxy status screen , though the status of gears are self-explanatory ,there are lot of other statistics --

·         Is there any description for  the all the statistics displayed in the screen.?

·         Can we have map the displayed  statistics to the  memory usage  to understand when the gears are allocated.

·         As mentioned in HAProxy documentation when the capacity (current sessions / total sessions )is

above 90%,a gear is added. We are not able to map this with the statistics displayed-Can you please let us know what we

should be looking at.

The logic for when a gear is added/removed is encapsulated in the Ruby Daemon (info/bin of the haproxy cartridge). This is unrelated to any of the stats displayed in the stats page.



2.       During Auto Scaling, is a new gear allocated only if there are concurrent session(Multiple Threads).?

For ex:

There is a small auto scaled app created to rapidly consume memory .If this is run in a single thread, it hits Out Of memory Issue and gear goes down.

If this is run in multiple thread mode, auto scaling works and gears are added/removed accordingly. Is this an expected behavior.?

Take a look at the Ruby Daemon - this is where all the logic for auto-scaling lives. The current algorithm is currently based entirely on the number of concurrent sessions. Memory usage is not part of the auto-scaling or load-balancing algorithm so yes that is expected behavior. On our roadmap we have the ability for users to customize the auto-scaler and to plug and customize other load-balancers (e.g. mod_cluster). For OSE and Origin the auto-scaler can be custoimized by the sysadmin.


3.       Need confirmation on the same – As per the documentation, The algorithm for scaling up and scaling down is not configurable currently both in

OpenShift Online and OS Enterprise.Is this  deduction right ?Do we have any plans for the same in future.?

The autoscaler is not currently configurable in Online except for the ability for the user to set the floor and ceiling on the number of instances. However it is customizable via the Ruby Daemon for OSE and Origin.


Thanks In Advance

Shabna MT





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