To better handle the case of images that don’t support concurrency, or don’t support log collection from invoker, I would suggest we change the container protocol to allow containers to broadcast their support either via the /init endpoint, or via a new /info endpoint. This of course would not give feedback until an action is executed (as opposed to when action is created), but I think this is ok. I will work on a separate PR for this, but want to mention some thoughts here about possible approaches to address these known concerns.
Why not make this part of the runtimes manifest? Handling this as late as actually invoking the action feels kinda weird if we can just as well know ahead of time, that creating an action with a concurrency > 1 will not work and should therefore forbid creation at all. Any strong reason not to encode that information into the runtimes manifest? One thing is blackbox containers - will only managed containers be allowed to support concurrency? If not, how will blackbox containers advertise support? Separately, the only thing that action creation currently does is validate “action build time” issues, like "do action limits fit within the allowed ranges”, it does not mean the input value is appropriate for execution. If the runtime manifest had per-image settings for all action limits, it would make more sense to include concurrency there - but I would have the same suggestion, that allowing the image to dictate the entirety of its opinions on these allowed ranges would be nicer to do as part of the container protocol (/init, /run), and not the manifest - partly for blackbox support, and partly because it is simpler to maintain just the image and just the manifest (which just references images, not the metadata of what the image supports internally). In any case, is this (per container metadata indicating concurrency support) really required for supporting concurrency at all? I agree it will be nice, but don’t think that it should block adding support for concurrency. WDYT? Thanks Tyson
