George Porter wrote:
One thing that you might consider is adding the ability to add path
state to the serialization to better support tracing and instrumentation
of the RPC layer with Avro.
Such cross-system tracing would be great, but I think this might best be
done as part of request and response metadata, rather than made part of
the user's request and response data.
You and I worked this nearly through for Hadoop's existing RPC:
http://issues.apache.org/jira/browse/HADOOP-4049
Unfortunately, that patch stalled awaiting benchmarks, and now is stale.
Avro currently specifies a request and response payload format, but
does not say much about metadata. In an HTTP-based transport, tracing
might be done through headers. As we adapt Hadoop's optimized RPC
transport to support Avro messages we should probably insert a generic
metadata layer, analogous to HTTP's headers, to support features such as
this.
Doug
