IOC Helm Chart Details

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IOC instances are described using a helm chart which in turn generates a Kubernetes manifest to tell Kubernetes what resources to create in order to run the IOC instance.

Here we will look inside the template IOC instance in the template domain repository blxxi-template.

You can see these files in Github here: epics-containers/blxxi-template

Examine the Example IOC Instance

Take a look in the folder services/blxxi-ea-ioc-01. This contains a helm chart that defines the example IOC instance. To make new IOC instance you could copy this folder into your own domain repository’s iocs folder. You would then need to rename it and make a few changes. Below is a description of the files in this folder and what you would need to change in your new IOC instance:

• Chart.yaml - this is the helm chart definition file. It contains metadata about the chart and a list of dependencies. Most of this file can be left as is for all IOC instances. But you do need to change these fields:

  • name - the unique name for the chart and the IOC instance it represents.

  • Description - a short description of the IOC instance.

• values.yaml - this is the helm values file. It contains the values that are substituted in to the helm templates when the helm chart is built. Most of the values that go into an IOC instance chart will be drawn from repository defaults which can be found in the folder helm/shared. Values you need to supply here are:

  • base_image - the Generic IOC image to use for this IOC instance. A Generic IOC image contains all the necessary support modules for a given class of device and a compiled IOC binary with all those modules linked. The IOC instance we are defining in a helm chart provides the startup script and possibly database that makes this IOC instance unique. In this case the Generic IOC is for the area-detector simulator device.

  • prefix - the EPICS PV prefix for this IOC instance. This will set an environment variable IOC_PREFIX which declares the prefix for the IOC’s devIOCStats records. You can leave this value out if you use the ioc name as the prefix, but in this case we have used an uppercase version of IOC name as the prefix.

• templates/ioc.yaml this is the master template for this helm chart, it pulls in all the other templates from our dependencies. This file has to appear here but is boilerplate and should not need to be changed.

• config this folder contains any files unique to this IOC instance. At runtime on the cluster when the Generic IOC image is running it will see these files as mounted into the folder /workspaces/epics/ioc/config. In this case we have an EPICS startup script st.cmd only and the default behaviour is just to run the IOC binary and pass it st.cmd.

  To see how the Generic IOC makes use of the config folder take a look at this bash script which runs on Generic IOC startup.

  If you want to have completely custom behaviour in your IOC instance, you can place a bash script called start.sh in the config folder this will run in place of the above script.