Context and Knative I view as orthogonal.
That is, for the context object, it is another way of encapsulating arguments.
It doesn’t export variable to the process environment.
You can provide an action with both environment variables, arguments to main,
and a context object. They are orthogonal.
For the context object, the distinction that was necessary from previous
discussions was related to separating intra container concurrent executions. If
the system-provided context is exported to the environment as it today the
values clobber each other. For this, the context object would make sense.
I’m simply talking about two parameters wsk ... “-p a A” and “-p B b” say
where one becomes exported to the environment as B=b and the other is passed to
the action as ({a:A}).
I’m going to set the knative discussion aside because I think it’s a
distraction. With knative you can bind environment variables to the container.
As you would with any other container.
I think it’s too simplistic to say knative has a single endpoint. After all
there are readiness probes and possible pre/post start hooks that operators may
have to deal with. Init can be viewed as the readiness probe.
Fundamentally I believe the actor model is much better aligned with the
reactive programming model for functions so this will tend toward a completely
different discussion in my view.
The reason my proposal sets the environment variables at init time is that’s
how env vars work; they exist before you start you process. While they don’t
need to be immutable, it makes sense to test them as such.
For webaction parameters that one would export to an environment, they are
already immutable and cannot be overridden. So really you would not use them
for anything that varies per activation.
The view here is that you can export global (immutable) variables to the
action. This makes it easier to take existing code and containers which might
use env vars and use them almost off the shelf.
-r
> On Jun 25, 2019, at 6:07 PM, Tyson Norris <tnor...@adobe.com.invalid> wrote:
>
> I had to read this several times, but have some suggestions. I think when you
> say "action's arguments", you mean action-configured params, e.g. `wsk action
> create --param p1 v1`?
>
> My preferences would be:
> - we should split off "run" args into context and params - this is the
> convention change for redefining main(args) as main(context, args) we have
> discussed in the past.
> - I support either having init receive action-configured params
> - activation args that are possibly overridden should behave exactly as
> specified args - is it important that action-configured args are actually
> overridden, if the context and params are separated? (receive both values,
> and logic must decide when to use which)
> - let's not use env variables for any arg that is variable per activation -
> it is impossible if you support concurrency, and unneeded if we pass the
> context to "run".
>
> Regarding Matt's suggestion to remove init - I like this idea, but I have
> concerns compared to knative which might serve every function with a
> different container, vs having some containers reused for multiple functions.
> In the case where we init code into an already running container, it is
> useful to have the init process separate from run, since otherwise each
> runtime will need to track its own init state and queue requests during init
> etc. If I'm not getting the whole picture with knative, please correct me.
>
>
> Thanks
> Tyson
>
> On 6/24/19, 8:43 AM, "Rodric Rabbah" <rod...@gmail.com> wrote:
>
> In the current activation model, an action's arguments are always provided
> to the action on "run", not "init".
>
> Should we consider partitioning the argument list into two sets, the first
> is exported as environment variables at "init" time, and the second become
> the action's argument at "run" time? A criteria for partitioning is that
> the environment variable starts with a capital letter, which is a common
> convention.
>
> For example, an action which is invoked with a JSON object
>
> { "XYZ": true,
> "abc" : false }
>
> would receive {"abc": false} as its arguments and can read XYZ from the
> environment (as process.env.XYZ == "true" in Node.js).
>
> This change would:
> 1. require a change in the invoker to pass arguments during initialization
>
> 2. require a change in the runtime proxies to export the arguments to the
> environment at initialization time (additional work may be implied by 1b)
>
> 3. an annotation on actions to opt into this partitioning for backward
> compatibility or to opt out. For example '-a env-partition-arguments true'
> partitions the arguments and actions without this annotation are not
> affected.
>
> Some obvious question:
> Q1a. should the invoker perform the partitioning or delegate it to the
> runtime? The advantage of the former is that the runtimes do not have to
> implement the filtering policy and do less work. I think it makes sense to
> do this invoker side for uniformity.
>
> Q1b. should the partitioning treat environment variables as immutable post
> init and ignore the partition on warm starts? This is an issue when a value
> is overridden during POST invoke only since for a webaction, you cannot
> override a value that's already defined (and updating a bound parameter on
> an action invalidates warm containers). I think env vars should be treated
> as immutable despite the issue with POST invoke.
>
> -r
>
>
