sjwiesman commented on pull request #303:
URL: https://github.com/apache/flink-statefun/pull/303#issuecomment-1050044752
By "us" I am referring to the StateFun SDK. Let's suppose in a future
version we add the pair `a=b` as a default bit of information to the
context[^1]. In the current implementation, where we are deriving a new context
with the pair `c=d`, that new `statefun.Context` will lose the original pair
`a=b`. This behavior differs from `context.Context.WithValue` which retains the
existing kv pairs when new ones are added. Maybe my example code should be
changed to create a new statefun context that contains the underlying contexts
and the new one, something like:
```go
type statefunContext struct {
*sync.Mutex
context.Context
merged []context.Context
self Address
caller *Address
storage *storage
response *protocol.FromFunction_InvocationResponse
}
func (s *statefunContext) WithAllValues(other context.Context) Context {
s.Lock()
defer s.Unlock()
return &statefunContext{
s.Mutex,
s.Context,
append(s.merged, other),
s.self,
s.caller,
s.storage,
s.response,
}
}
func (s *statefunContext) Value(key interface{}) interface{} {
for i := len(s.merged) - 1; i >= 0; i-- {
if result := s.merged[i].Value(key); result != nil {
return result
}
}
return s.Context.Value(key)
}
```
While I realize in go you can at any point create a new context that
discards all underlying data, that doesn't seem like a usage pattern we want to
encourage.
[^1]: A real example, I can imagine adding tracing information into the
invocations in the near future.
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