REAPI v3 (Remote Execution API)

[tdyas]

There is some discussions going on in the Bazel + others build tools community about v3 of REAPI (Remote Execution API). Pants supports REAPI as the "remote environment" via remote_environment target type.

Discussion on the future of REAPI v3 was happening in https://docs.google.com/document/d/1FxpdOzOhzOCTjjn2loppMlBzjqjU9WpYF4E1K6opxVI/edit?usp=sharing

I am opening this discussion as a place for Pants developers to talk about our understanding of REAPI v3 direction, implications for Pants, and future actions we may want to or need to take.

[tdyas]

Questions asked by Ed Schouten of REAPI v3 working froup to build tools teams:

On behalf of the working group, I would like to invite authors of such
tools to give the previously linked document a read and get back to us
to answer the following questions. Note that we're interested in
receiving feedback even if your implementation is proprietary or used
within a private setting.

1. Of the topics discussed in the document, which parts would you like
   the working group to focus on most? Phrased differently: which of the
   issues described in the document are currently most problematic for
   your client/server?

2. Are there any topics that are not covered by the document that you
   wish they were?

3. Assuming a new version of the remote execution protocol is released
   with the aforementioned changes made, do you think that it brings
   enough value that your client/server should be extended to support it?

4. Assuming implementing the parts of the new protocol take a similar
   amount of effort as REv2, do you think your project has a sufficient
   amount of staffing/headcount/momentum to implement the new protocol?
   Note that this does not need to be a firm commitment.

[tdyas]

The Pants append-only cache feature (also known as "named" caches) does not work well with remote execution since the protocol does not provide for storage to persist between remote build actions. Should we ask for thought to be given to such a feature?

[cburroughs]

Prior related writeup: https://groups.google.com/g/remote-execution-apis/c/mA87-IDNpec?pli=1