Context Propagation in Java

[hsaliak]

Provide documentation around Context propagation

• I want to propagate user credential/token across multiple calls
• I want to propagate trace ID of some sort across multiple calls
• Does it only propagate one way down the calls?
• How is it different from metadata?
• Context = in-process

Currently marking this as Java only since the mechanisms are slightly different across the runtimes. For example, in Go, context propagation follows language idiomatic guidelines and is well described in the examples already.

[natemurthy]

I'ld also like to see some documentation around best practices for in-process context propagation for the Java gRPC library. Here is some existing literature on the subject:

• https://github.com/opentracing/specification/issues/23
• https://github.com/uber/jaeger-client-java#in-process-context-propagation