Reads and writes gRPC trace and tags binary metadata #688
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I need to add an interop test to prove this actually works cc @bogdandrutu |
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note this will be refactored to be optional behavior |
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| @Test public void readsPropagatedSpan() throws Exception { |
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here's the test that shows we are participating in the same trace
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added censusPropagationEnabled property and client+server tests |
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going to add tags propagation as well, as we can lose it otherwise.. |
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refactored to not drop tag context |
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not-dropping is probably not good enough, as the last upstream part of the tag context should be replaced.. |
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ok rewrote everything. tags now works |
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| spanId = readLong(bytes, pos); | ||
| pos += 8; | ||
| } else { | ||
| logger.fine("Invalid input: expected span ID at offset " + pos); |
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self-note: kill all these string cats as they shouldn't happen unless fine is enabled
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| To enable this feature, set `grpcPropagationFormatEnabled` which is off | ||
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| ```java |
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To give most flexibility I made this a feature flag similar to how tracing is still a flag in gRPC
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going to release this tomorrow unless screams to the contrary |
This prefers the OpenCensus binary formatted trace header, falling back to Brave defaults if absent, upon server requests. On the client side, both are written. This allows interop with gRPC services that don't use B3 (for example, the default census module). This also acknowledges that the OpenCensus binary format is fairly contained within gRPC, so doesn't need to become a top-level propagation format, for example used with non-gRPC services as yet. Redundantly encoding this format has some cost to it, notable 14 character header name "grpc-trace-bin" and the 38 character base64 encoded binary context value. This also writes "grpc-tags-bin". Note that this only allows black-box interop with Census. It does not (yet) interop with census in the same process as Brave. However, this should be a helpful step to those especially currently using Brave, but trying out Census for non-java services.
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gRPC Propagation Format (Census interop)
gRPC defines a binary encoded propagation format which is implemented
by OpenCensus instrumentation. When this is
the case, incoming requests will have two metadata keys "grpc-trace-bin"
and "grpc-tags-bin".
When enabled, this component can extract trace contexts from these
metadata and also write the same keys on outgoing calls. This allows
transparent interop when both census and brave report data to the same
tracing system.
To enable this feature, set
grpcPropagationFormatEnabledwhich is offby default:
Warning: the format of both "grpc-trace-bin" and "grpc-tags-bin" are
version 0. As such, consider this feature experimental.
notes:
This allows interop with gRPC services that don't use B3 (for example,
the default census module). This also acknowledges that the OpenCensus
binary format is fairly contained within gRPC, so doesn't need to become
a top-level propagation format, for example used with non-gRPC services
as yet.
Redundantly encoding this format has some cost to it, notable 14
character header name "grpc-trace-bin" and the 38 character base64
encoded binary context value.
Note that this only allows black-box interop with Census. It does not
(yet) interop with census in the same process as Brave. However, this
should be a helpful step to those especially currently using Brave, but
trying out Census for non-java services.
See #626