What would you like to happen?
I'd like to port the Wait.On functionality of Java to the Go SDK, so that runtime ordering constraints can be added between transforms without requiring modification of the transforms.
I often have operations which rely on side-effects (eg database writes having completed, GCS storage, BigTable updates, etc). In order to sequence these operation in Go, I end up wiring in completion signals manually into producers and then side-inputs into consumers. This is effectively a manual implementation of wait.On which reduces composability of the operations since it means the shape of the operation has to be modified for the particular situation.
The goal would be to provide a transforms/wait package containing an On method:
// To finish writing each window to one database before writing it
// to another:
firstWriteResults := beam.ParDo(s, writeToFirstDB, data)
delayed := wait.On(s, data, firstWriteResults)
beam.ParDo0(s, writeToSecondDB, delayed)
Where On would look like this:
// On returns col unchanged, but delays each main window until its mapped window
// has closed in every signal.
//
// With no signals, On validates s and col and returns col directly. Otherwise,
// it panics at pipeline construction time for an invalid scope or PCollection,
// CoGBK inputs, or session-windowed signals.
func On(s beam.Scope, col beam.PCollection, signals ...beam.PCollection) beam.PCollection {Issue Priority
Priority: 2 (default / most feature requests should be filed as P2)
Issue Components
What would you like to happen?
I'd like to port the Wait.On functionality of Java to the Go SDK, so that runtime ordering constraints can be added between transforms without requiring modification of the transforms.
I often have operations which rely on side-effects (eg database writes having completed, GCS storage, BigTable updates, etc). In order to sequence these operation in Go, I end up wiring in completion signals manually into producers and then side-inputs into consumers. This is effectively a manual implementation of
wait.Onwhich reduces composability of the operations since it means the shape of the operation has to be modified for the particular situation.The goal would be to provide a transforms/wait package containing an
Onmethod:Where
Onwould look like this:Issue Priority
Priority: 2 (default / most feature requests should be filed as P2)
Issue Components