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.
> > > > > > >> >
> > > > > > >>
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>
