feat(mcp-python): move instrumentation to transport layer #1563
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codefromthecrypt
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thanks for keeping the code coherent across languages
mikeldking
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| # While we prefer to instrument the lowest level primitive, the transports above, it doesn't | ||
| # mean context will be propagated to handlers automatically. Notably, the MCP SDK passes | ||
| # server messages to a handler with a separate stream in between, losing context. We go | ||
| # ahead and instrument this second stream just to propagate context so transports can still | ||
| # be used independently while also supporting the major usage of the MCP SDK. Notably, this | ||
| # may be a reasonable generic instrumentation for anyio itself to allow its streams to | ||
| # propagate context broadly. |
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thanks for the explanation here.
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This is the same as #1555 for Python. There is some more effort here because of the message passing model used causing context breaks within the SDK between transport and handler. While we could continue to instrument at the higher level than handler, I thought it's still better to keep as similar between the languages as possible and instead instrumented the message passing itself as well for in-process context propagation.
I also went ahead and bumped the supported version because there were significant changes to how client message handling is done
https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.6.0
It seemed simpler to raise the target since this is new instrumentation, though targeting both admittedly has a much larger impact on the tests than the instrumentation itself.
/cc @codefromthecrypt