Hi,
If i have a ValueTransformer that wraps another ValueTransformer like:
class WrappingValueTransformer<V, VR> implements ValueTransformer<V, VR> {
....
final ValueTransformer<V, VR> delegateTransformer;
ProcessorContext processorContext;
WrappingValueTransformer(ValueTransformer<V, VR> delegateTransformer) {
this.delegateTransformer = delegateTransformer;
}
@Override
public void init(ProcessorContext processorContext) {
this.processorContext = processorContext;
delegateTransformer.init(processorContext);
}
@Override
public VR transform(V v) {
....
VR transform = delegateTransformer.transform(v);
....
return transform;
}
@Override
public void close() {
delegateTransformer.close();
}
}
Should the Supplier for this wrapper ensure that the delegate transformer is
also instantiated anew each time, like:
() -> return new WrappingValueTransformer(new AnotherValueTransformer());
Or can the WrappingValueTransformer hold on to the transformer it wraps, like:
ValueTransformer t = new AnotherValueTransformer();
() -> return new WrappingValueTransformer(t);
Reason i'm asking is that over in openzipkin/brave there is an
IllegalStateException (https://github.com/openzipkin/brave/issues/982) occuring
when accessing ProcessorContext#headers() during transform() from a
ValueTransformer that is wrapped in TracingValueTransformer. A fix seems to be
to make sure that the wrapping transformer also instantiates anew the
transformer it wraps. But according to ProcessorContext semantics this does not
seem necessary, as init() is called each time which guarantees correct setup of
the context on the transformer. Can anyone shed light on this ?
Regards,
Jorg Heymans
