Instead of passing the transport byte counts back up through the filter
stack to be reported to the `CallTracer`, we now have the transport
pass the transport byte counts directly to the `CallTracer` itself.
This will eventually allow us to avoid unnecessarily storing these byte
counts in cases where no `CallTracer` actually cares about the data, which
will reduce per-call memory. (In the short term, it actually increases
memory usage, but we can separately do some work to avoid the memory
usage in the transport by removing the `grpc_transport_stream_stats`
struct from the legacy filter API.)
This is a prereq for supporting `CallTracer` in the new call v3 stack,
which does not include the transport byte counts as part of the
receieve-trailing-metadata hook, unlike the legacy filter stack.
This change is controlled by the `call_tracer_in_transport` experiment,
which is enabled by default.
As part of this experiment, we also fix a couple of related bugs:
- On the client side, the chttp2 transport was incorrectly adding
annotations to the parent `ClientCallTracer` instead of the
`CallAttemptTracer`.
- The OpenCensus `ServerCallTracer` was incorrectly swapping the values
of sent and received bytes.
PiperOrigin-RevId: 650728181
Implement Python CSM observability.
Design: [go/grpc-python-opentelemetry](http://goto.google.com/grpc-python-opentelemetry)
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Closes#36557
Core team [moved resolver code](https://github.com/grpc/grpc/pull/35804) to `src/core/resolver`, our build is failing because we have a dependency on it and the resolver folder is not copied to `observability/grpc_root`:
* `call_tracer.h` -> `core_configuration.h` -> `lb_policy_registry.h` -> `lb_policy.h` -> `endpoint_addresses.h`
To fix this issue and to prevent such issues from happening again, instead of subfolders, we'll copy all files from `src/core` to `observability/grpc_root/src/core`.
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Closes#35845
This new directory combines code from the following locations:
- src/core/ext/filters/client_channel/lb_policy
- src/core/lib/load_balancing
Closes#35786
### Changes in this PR
* Refactor and remove some Core/C++ dependencies to simplify Python Observability package build process.
* Refactored code to read config at Python layer.
* Enable observability build from source.
* Add observability to run_test.
* Currently it's only enabled in Linux.
* Add error handler in run_test loaders.
* Current framework will always visit modules in test directory then decide which tests to skip.
* Since we're not building Observability for MacOS and Windows this step will fail with error `No module named 'grpc_observability'`.
* After the change we'll just skip those modules.
* We still have `_sanity_test` to make sure all tests are loaded correctly for each platform.
* Remov OC dependency as we're migrating to OTel.
* Also removed trace from testing.
* Note that trace propagation function was also removed because of this.
### Testing
* Passed existing tests.
* Tested locally, able to build observability from source using `GRPC_PYTHON_BUILD_WITH_CYTHON=1 pip install .`.
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Closes#34207
Mark D. Roth
Xuan Wang