Ha, our emails keep passing.
I've been playing around with options locally, and the SetContext option
seems to be the most flexible (and non-breaking), imo.
The implementation would be trivial, just add:
SetContext(ctx context.Context)
... to the statefun.Context interface, which is implemented as:
func (s *statefunContext) SetContext(ctx context.Context) {
s.Context = ctx
}
On Fri, Feb 18, 2022 at 11:18 AM Austin Cawley-Edwards <
austin.caw...@gmail.com> wrote:
> It would be helpful to have a small example though, if you have on Galen,
> to see how you're passing it around.
>
> On Fri, Feb 18, 2022 at 11:10 AM Austin Cawley-Edwards <
> austin.caw...@gmail.com> wrote:
>
> > Looking through the statefun Context interface, it indeed doesn't give
> > access to the underlying context.Context and the only implementation is
> > package-private [1]. I don't think there would be a way to update the
> > statfun.Context interface without introducing breaking changes, but if we
> > were to make that implementation public, that might be a stopgap
> solution.
> > e.g.,
> >
> > ```
> > type StatefunContext struct {
> > // expose embedded context
> > context.Context
> >
> > // make the mutext private
> > mu sync.Mutex
> >
> > // keep internals private
> > self Address
> > caller *Address
> > storage *storage
> > response *protocol.FromFunction_InvocationResponse
> > }
> > ```
> >
> > You could then do a type assertion in the handlers for this type of
> > context, and modify the context on it directly. It would be a bit ugly,
> but
> > may work.
> >
> > ```
> > func (s aFunc) Invoke(ctx Context, message Message) error {
> > if sCtx, ok := ctx.(*statefun.StatefunContext); ok {
> > sCtx.Context = context.WithValue(sCtx.Context, "logger", aLogger)
> > }
> > // ...
> > }
> > ```
> >
> > Let me know what you all think,
> > Austin
> >
> >
> > [1]:
> >
> https://github.com/apache/flink-statefun/blob/1dfe226d85fea05a46c8ffa688175b4c0f2d4900/statefun-sdk-go/v3/pkg/statefun/context.go#L66-L73
> >
> >
> > On Fri, Feb 18, 2022 at 11:03 AM Galen Warren <ga...@cvillewarrens.com>
> > wrote:
> >
> >> Sorry Austin, I didn't see your response before I replied. Yes, we're
> >> saying the same thing.
> >>
> >> On Fri, Feb 18, 2022 at 10:56 AM Austin Cawley-Edwards <
> >> austin.caw...@gmail.com> wrote:
> >>
> >> > Hey all, jumping in. This makes sense to me – for instance to attach a
> >> > logger with some common metadata, e.g trace ID for the request? This
> is
> >> > common in go to add arbitrary items without updating the method
> >> signatures,
> >> > similar to thread local storage in Java.
> >> >
> >> > On Fri, Feb 18, 2022 at 10:53 AM Till Rohrmann <trohrm...@apache.org>
> >> > wrote:
> >> >
> >> > > Thanks for the clarification Galen. If you call the other Go
> >> functions,
> >> > > then you could also pass the other values as separate arguments to
> >> these
> >> > > functions, can't you?
> >> > >
> >> > > Cheers,
> >> > > Till
> >> > >
> >> > > On Fri, Feb 18, 2022 at 3:31 PM Galen Warren <
> ga...@cvillewarrens.com
> >> >
> >> > > wrote:
> >> > >
> >> > > > The former.
> >> > > >
> >> > > > I think there's potential for confusion here because we're using
> the
> >> > > > word *function
> >> > > > *in a couple of senses. One sense is a *stateful function*;
> another
> >> > sense
> >> > > > is a *Go function*.
> >> > > >
> >> > > > What I'm looking to do is to put values in the Context so that
> >> > downstream
> >> > > > Go functions that receive the context can access those values.
> Those
> >> > > > downstream Go functions would be called during one invocation of
> the
> >> > > > stateful function.
> >> > > >
> >> > > > On Fri, Feb 18, 2022 at 6:48 AM Till Rohrmann <
> trohrm...@apache.org
> >> >
> >> > > > wrote:
> >> > > >
> >> > > > > Hi Galen,
> >> > > > >
> >> > > > > Am I understanding it correctly, that you would like to set some
> >> > values
> >> > > > in
> >> > > > > the Context of function A that is then accessible in a
> downstream
> >> > call
> >> > > of
> >> > > > > function B? Or would you like to set a value that is accessible
> >> once
> >> > > > > function A is called again (w/ or w/o the same id)?
> >> > > > >
> >> > > > > Cheers,
> >> > > > > Till
> >> > > > >
> >> > > > > On Thu, Feb 17, 2022 at 10:59 PM Galen Warren <
> >> > ga...@cvillewarrens.com
> >> > > >
> >> > > > > wrote:
> >> > > > >
> >> > > > > > Also, a potentially simpler way to support this would be to
> add
> >> a
> >> > > > > > SetContext method to the statefun.Context interface, and have
> it
> >> > > assign
> >> > > > > the
> >> > > > > > wrapped context. This would not require changes to the
> function
> >> > spec,
> >> > > > or
> >> > > > > > anything else, and would be more flexible.
> >> > > > > >
> >> > > > > > On Thu, Feb 17, 2022 at 1:05 PM Galen Warren <
> >> > > ga...@cvillewarrens.com>
> >> > > > > > wrote:
> >> > > > > >
> >> > > > > > > Thanks for the quick reply!
> >> > > > > > >
> >> > > > > > > What I'm trying to do is put some things into the context so
> >> that
> >> > > > > they're
> >> > > > > > > available in downstream calls, perhaps in methods with
> pointer
> >> > > > > receivers
> >> > > > > > to
> >> > > > > > > the function struct (MyFunc) but also perhaps in methods
> that
> >> are
> >> > > > > further
> >> > > > > > > downstream that don't have access to MyFunc. If I'm
> >> understanding
> >> > > > > > > correctly, your proposal would work for the former but not
> the
> >> > > > latter.
> >> > > > > > >
> >> > > > > > > An example would be to put a configured Logger into the
> >> context
> >> > > via a
> >> > > > > > > WithLogger method (logging package -
> knative.dev/pkg/logging
> >> -
> >> > > > > > pkg.go.dev
> >> > > > > > > <https://pkg.go.dev/knative.dev/pkg/logging#WithLogger>)
> and
> >> > then
> >> > > > pull
> >> > > > > > it
> >> > > > > > > out downstream via FromContext (logging package -
> >> > > > > > knative.dev/pkg/logging
> >> > > > > > > - pkg.go.dev <
> >> > > https://pkg.go.dev/knative.dev/pkg/logging#FromContext
> >> > > > > >).
> >> > > > > > >
> >> > > > > > >
> >> > > > > > >
> >> > > > > > >
> >> > > > > > > On Wed, Feb 16, 2022 at 5:50 PM Seth Wiesman <
> >> > sjwies...@gmail.com>
> >> > > > > > wrote:
> >> > > > > > >
> >> > > > > > >> Hi Galen,
> >> > > > > > >>
> >> > > > > > >> No, that is not currently supported, the current idiomatic
> >> way
> >> > > would
> >> > > > > be
> >> > > > > > to
> >> > > > > > >> pass those values to the struct implementing the Statefun
> >> > > interface.
> >> > > > > > >>
> >> > > > > > >>
> >> > > > > > >> type MyFunc struct { someRuntimeInfo string } func (m
> >> *MyFunc)
> >> > > > > > Invoke(ctx
> >> > > > > > >> statefun.Context, message statefun.Message) error { } func
> >> > main()
> >> > > {
> >> > > > > > >> builder
> >> > > > > > >> := statefun.StatefulFunctionsBuilder()
> >> > > > > > >> f := MyFunc { someRuntimeInfo: "runtime-provided" }
> >> > > builder.WithSpec
> >> > > > > > >> (statefun.StatefulFunctionSpec{ FunctionType:
> >> > > statefun.TypeNameFrom(
> >> > > > > > >> "example/my-func"), Function: f })
> >> > > > > > >> http.Handle("/statefun", builder.AsHandler())
> >> > > > > > >> _ = http.ListenAndServe(":8000", nil) }
> >> > > > > > >>
> >> > > > > > >> Would this work for you? Or what is the context (pun
> >> intended)
> >> > you
> >> > > > are
> >> > > > > > >> looking for?
> >> > > > > > >>
> >> > > > > > >> Seth
> >> > > > > > >>
> >> > > > > > >> On Wed, Feb 16, 2022 at 4:35 PM Galen Warren <
> >> > > > ga...@cvillewarrens.com
> >> > > > > >
> >> > > > > > >> wrote:
> >> > > > > > >>
> >> > > > > > >> > When stateful functions are invoked, they are passed an
> >> > instance
> >> > > > of
> >> > > > > > >> > statefun.Context, which wraps the context.Context
> received
> >> by
> >> > > the
> >> > > > > HTTP
> >> > > > > > >> > request. Is there any way to customize that
> context.Context
> >> > to,
> >> > > > say,
> >> > > > > > >> hold
> >> > > > > > >> > custom values, using ctx.WithValue()? I don't see a way
> >> but I
> >> > > > wanted
> >> > > > > > to
> >> > > > > > >> > ask.
> >> > > > > > >> >
> >> > > > > > >> > If not, would you be interested in a PR to add this
> >> > > > functionality? A
> >> > > > > > >> simple
> >> > > > > > >> > way might be to add a property to StatefulFunctionSpec,
> >> say:
> >> > > > > > >> >
> >> > > > > > >> > TransformContext func(ctx context.Context)
> context.Context
> >> > > > > > >> >
> >> > > > > > >> > ... that, if supplied, would be called to create a
> >> customized
> >> > > > > context
> >> > > > > > >> that
> >> > > > > > >> > would be used downstream?
> >> > > > > > >> >
> >> > > > > > >> > Thanks.
> >> > > > > > >> >
> >> > > > > > >>
> >> > > > > > >
> >> > > > > >
> >> > > > >
> >> > > >
> >> > >
> >> >
> >>
> >
>
