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Managing Application Resource Limits

Deis Workflow supports restricting memory and CPU shares of each process. Limits set on a per-process type are given to Kubernetes as both a request and limit. Which means you guarantee 'X' amount of resource for a process as well as limit the process from using more than 'X'.

Limiting Memory

If you set a limit that is out of range for your cluster, Kubernetes will be unable to schedule your application processes into the cluster!

Available units for memory are:

Unit Amount
B Bytes
K KiB (Power of 2)
M MiB (Power of 2)
G GiB (Power of 2)

!!! important The minimum memory limit allowed is 4MiB.

Use deis limits:set to restrict memory by process type:

$ deis limits:set web=128M
Applying limits... done

=== indoor-whitecap Limits

--- Memory
web     64M

--- CPU
Unlimited

If you would like to remove any configured memory limits use deis limits:unset web:

$ deis limits:unset web
Applying limits... done

=== indoor-whitecap Limits

--- Memory
Unlimited

--- CPU
web     250m

Limiting CPU

You can also use deis limits:set -c to restrict CPU shares. CPU shares are tracked in milli-cores. One CPU core is equivalent to 1000 milli-cores. To dedicate half a core to your process, you would need 500 milli-cores or 500m.

Unit Amount
1000m 1000 milli-cores == 100% CPU core
500m 500 milli-cores == 50% CPU core
250m 250 milli-cores == 25% CPU core
100m 100 milli-cores == 10% CPU core 
$ deis limits:set web=250m -c
Applying limits... done

=== indoor-whitecap Limits

--- Memory
web     64M

--- CPU
web     250m

You can verify the CPU and memory limits by inspecting the application process Pod with kubectl:

$ deis ps
=== indoor-whitecap Processes
--- web:
indoor-whitecap-v14-web-8slcj up (v14)
$ kubectl --namespace=indoor-whitecap describe po indoor-whitecap-v14-web-8slcj
Name:       indoor-whitecap-v14-web-8slcj
Containers:
    QoS Tier:
      cpu:  Guaranteed
      memory:   Guaranteed
    Limits:
      cpu:  250m
      memory:   64Mi
    Requests:
      memory:       64Mi
      cpu:      250m

!!! important If you restrict resources to the point where containers do not start, the limits:set command will hang. If this happens, use CTRL-C to break out of limits:set and use limits:unset to revert.

To unset a CPU limit use deis limits:unset web -c:

$ deis limits:unset web -c
Applying limits... done

=== indoor-whitecap Limits

--- Memory
Unlimited

--- CPU
Unlimited