sven-lange-last commented on a change in pull request #4627: Add descriptions 
how to update, remove or rename runtime kinds and language families

 File path: docs/
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+## Updating Action Language Runtimes
+OpenWhisk supports [several languages and 
runtimes]( that can be made
+available for usage in an OpenWhisk deployment. This is done via the [runtimes 
+Over time, you may have the need for change:
+* Update runtimes to address security issues - for example, the latest code 
level of Node.js 10.
+* Remove runtime versions that are no more supported - for example, Node.js 6.
+* Add more languages due to user demand.
+* Remove languages that are no more needed.
+While adding and updating languages and runtimes is pretty straightforward, 
removing or renaming languages and runtimes
+requires some caution to prevent problems with existing actions.
+### Updating runtimes
+Follow these steps to update a particular runtime kind:
+1. Update the runtimes' container image.
+2. Update the corresponding `image` property in the [runtimes 
manifest]( to use the new container image.
+3. Restart / re-deploy controllers and invokers such that they pick up the 
changed runtimes manifest.
+Already existing actions of the changed runtime kind will immediately use the 
new container image when the invoker creates a new action container.
+Apparently, this approach should only be used if existing actions do not break 
with the new container image. If a new container image is supposed to break 
existing actions, introduce a new runtime kind.
+### Removing runtimes
+Follow these steps to remove a particular runtime kind under the assumption 
that actions with the runtime kind exist in the system. Apparently, it makes 
sense to wait some time between accomplishing these steps to give action owners 
time to react.
+1. Deprecate the runtime kind by setting `"deprecated": true` in the [runtimes 
manifest]( This setting prevents that new 
actions can be created with the deprecated action kind. In addition, existing 
actions cannot be changed to the deprecated action kind any more.
+2. Ask owners of existing actions with runtime kind to be removed to update 
their actions to a different action kind.
+3. Create an automated process that identifies all actions with the runtime 
kind to be removed in the system's action artifact store. Either automatically 
remove these actions or change to a different runtime kind.
+4. Once the system's action artifact store does no more contain actions with 
the runtime kind to be removed, remove the runtime kind from the [runtimes 
+5. TODO - is this correct?: Remove the runtime kind from the list of known 
kinds in the `ActionExec` object of the [controller API's Swagger 
 Review comment:
   I'm not sure where the Swagger is exactly used. The controller itself offers 
an endpoint where it publishes the supported runtimes - and this seems to base 
on the runtimes manifest, not the Swagger definition. See for example:

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