Invoke local using Docker to support any runtime

[alexkli]

Problem

Currently, serverless invoke local is implemented for nodejs and python runtimes by simply running a local Node or Python with the right script. It does not replicate the actual container environment nor does it work for other runtimes or custom images (blackboxes).

Idea

Add a new option to invoke local that relies on a local Docker and would act like an OpenWhisk invoker:

1. identify the right image - either explicit image in serverless.yml or lookup based on runtime (kind in wsk)
2. start the container using Docker
3. post the packaged action to /init on the server on port 8080
4. execute it via /run
5. kill the container

In our case, we'd like to use this for unit testing of actions with custom containers, and for that we'd need volume mounting on the container to make our life a lot easier. To keep it simple, it would be good to allow passing any additional docker run options from the serverless invoke local arguments.

State

We are intending to work on this and provide this as PR if desired.

[jthomas]

This would be an awesome feature. It would massively improve the developer experience. Great suggestion 💯.

Adding this feature could require a significant amount of code. As discussed, we don't want to require docker support for invoke local but provide this as an additional feature.

I wonder if it is possible to have a serverless invoke docker command?

SInce this would be a significant change, do you want to start with a prototype plugin? If we can get a basic version working and collaborate on the user experience, we can then assess whether to merge it back into the main provider code or keep as a separate plugin.

[alexkli]

Finally implemented this: https://gist.github.com/alexkli/88a7be93cd45f078bac49170a42ea093

It requires docker (obviously) and supports two "modes":

1. Build & run action once:

   sls invoke local -f action -p key value
   

2. Reuse container for repeated invocations: Start the container using --start, then reuse it for faster repeated invocations (no need to rebuild and start container every single time), and kill it using --stop at the end.

   # start container & init action
   sls invoke local -f action --start
   
   # invoke action multiple times
   sls invoke local -f action -p key value
   sls invoke local -f action -p key value2
   
   # check if running
   sls invoke local -f action --status
   # kill container
   sls invoke local -f action --stop
   

This is currently part of a custom serverless plugin. Because of that it has to do disableOpenwhiskPlugin() which is a bit of a workaround.

I think it would be nice to merge this into invoke local of the serverless-openwhisk plugin. Unless there are many people relying on the existing behavior (without changing cli args), I would suggest to keep support for the existing nodejs/python invocation style, but only if another flag such as --no-docker was provided.

[jthomas]

Hello @alexkli. Nice to see you got this working!

Can you start by exposing this as an official external SLS FW plugin that people can install as an additional feature? It will allow people to test it out and see how popular it is.

[jthomas]

Closing this ticket for the time being due to lack of activity.