census: update opencensus library to 0.28.1

[gfelbing]

Update OpenCensus to 0.28.1

Problem

The most recent update of OpenCensus contains a breaking change, namely making ContextUtils package private: census-instrumentation/opencensus-java@f8ea9bb#diff-3e846235e5a45651f4f79c6c7b4a325fe1b33a8e75ace3c188dd6104bd3e6dfa

Our project depends on opencensus as well as on grpc-java.
Unfortunately, we cannot update opencensus in our build as it would update the transitive dependency causing runtime errors due to that breaking change.

Solution

Updating OpenCensus to recent version, fixing the issue with the breaking change.

The call to ContextUtils.getValue can be replaced by Tracing.getTracer().getCurrentSpan(), as it calls ContextUtils.getValue(Context.current()); under the hood yielding the same behavior

Fixes

• OpenCensus 0.26.0 update #6928
• opencensus 0.28.1 breaks gRPC census-instrumentation/opencensus-java#2069

[linux-foundation-easycla]

The committers are authorized under a signed CLA.

• ✅ Georg Welzel (09e8958)

[gfelbing]

@jsuereth removes the breaking change in census-instrumentation/opencensus-java#2072.
Still, the ContextUtils will remain deprecated, suggesting to use the ContextHandleUtils.

[ejona86]

I'd have to dig a bit to confirm this change will work even if the gRPC context is not being used. But upgrading now to 0.28.1 will further propagate that broken Census release. I think we'll want to wait for a fixed release and then fix the API call. (But we can have this ready for once the Census release is available.)

[ejona86]

CC @voidzcy

[voidzcy]

Shouldn't this just be a no-op migration from ContextUtils to ContextHandleUtils?

[ejona86]

CC @ericgribkoff

[larry-safran]

This has become irrelevant since grpc is now using version 0.31.0