require() deployed nodejs function instead of executing inline

[ianserlin]

Issue Ref: #779

Description:

A simple change to how the user's code is run in kubeless.js allows webpacked functions to work out of the box and requires no changes to the way existing non-webpacked functions are written or deployed.

Note that this change means the user's function code is require()-d from disk on each run instead of being read as a string into memory once on pod startup.

However, this has a negligible effect on performance for the following reasons:

1. Most real-world functions are non-trivial and will have dependencies.
2. Some significant percentage of the time, webpacking all the dependencies into a single js file (which could be read into memory) will result in a payload size greater than 1mb, which is Kubeless' function size limit.
3. Those real-world functions will have to take advantage of Kubeless' dependency installation support on deployment.

That means that the size of code loaded as dependencies from disk will typically far outweigh the size of the function itself, making this one additional load from disk negligible as long as this package management solution is used.

Hope that makes sense.

TODOs:

• Ready to review
• Automated Tests: existing tests pass, no new tests needed
• Docs: no new docs needed, it will just work with webpacked functions from now on

[andresmgot]

Thanks for the PR @ianserlin. It looks good to me but can you add a small section in the runtimes.md file, in the NodeJS section, to explain how to use functions "webpacked"?

[ianserlin]

@andresmgot Roger that, added instructions and sample to the runtimes.md docs.

[andresmgot]

Thank you for updating the docs. One more thing, can you build and push (to your own repo) the nodejs images and change the reference at kubeless-non-rbac.jsonnet? That way CircleCI will test the changes. I will push them to the kubeless repo afterwards.

[SomeoneWeird]

This would be useful for us as well, do we just need CircleCI to go green before we can land this?

[andresmgot]

yes, we need to build the image and change the kubeless-non-rbac.jsonnet to test the changes. We also need to fix the conflict with the docs.

[bbeesley]

Any chance of getting this progressed? Being unable to run webpacked code is severely limiting the usefulness of the nodejs support here.

[andresmgot]

cc/ @ianserlin are you able to continue with this?

[ianserlin]

Yes, I can work on the requested changes this week. We've already gone to production with this setup.

[richardPFisk]

This is very useful addition. And, the accompanying explanation is useful too. Keep going 👍

[andresmgot]

Landing this since it has been rebased. Thank you all for the input and sorry for the slow response!