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tarpc is now instrumented with tracing primitives extended with OpenTelemetry traces. Using a compatible tracing-opentelemetry subscriber like Jaeger, each RPC can be traced through the client, server, amd other dependencies downstream of the server. Even for applications not connected to a distributed tracing collector, the instrumentation can also be ingested by regular loggers like env_logger. # Breaking Changes ## Logging Logged events are now structured using tracing. For applications using a logger and not a tracing subscriber, these logs may look different or contain information in a less consumable manner. The easiest solution is to add a tracing subscriber that logs to stdout, such as tracing_subscriber::fmt. ## Context - Context no longer has parent_span, which was actually never needed, because the context sent in an RPC is inherently the parent context. For purposes of distributed tracing, the client side of the RPC has all necessary information to link the span to its parent; the server side need do nothing more than export the (trace ID, span ID) tuple. - Context has a new field, SamplingDecision, which has two variants, Sampled and Unsampled. This field can be used by downstream systems to determine whether a trace needs to be exported. If the parent span is sampled, the expectation is that all child spans be exported, as well; to do otherwise could result in lossy traces being exported. Note that if an Openetelemetry tracing subscriber is not installed, the fallback context will still be used, but the Context's sampling decision will always be inherited by the parent Context's sampling decision. - Context::scope has been removed. Context propagation is now done via tracing's task-local spans. Spans can be propagated across tasks via Span::in_scope. When a service receives a request, it attaches an Opentelemetry context to the local Span created before request handling, and this context contains the request deadline. This span-local deadline is retrieved by Context::current, but it cannot be modified so that future Context::current calls contain a different deadline. However, the deadline in the context passed into an RPC call will override it, so users can retrieve the current context and then modify the deadline field, as has been historically possible. - Context propgation precedence changes: when an RPC is initiated, the current Span's Opentelemetry context takes precedence over the trace context passed into the RPC method. If there is no current Span, then the trace context argument is used as it has been historically. Note that Opentelemetry context propagation requires an Opentelemetry tracing subscriber to be installed. ## Server - The server::Channel trait now has an additional required associated type and method which returns the underlying transport. This makes it more ergonomic for users to retrieve transport-specific information, like IP Address. BaseChannel implements Channel::transport by returning the underlying transport, and channel decorators like Throttler just delegate to the Channel::transport method of the wrapped channel. # References [1] https://github.com/tokio-rs/tracing [2] https://opentelemetry.io [3] https://github.com/open-telemetry/opentelemetry-rust/tree/main/opentelemetry-jaeger [4] https://github.com/env-logger-rs/env_logger
12 lines
137 B
TOML
12 lines
137 B
TOML
[workspace]
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resolver = "2"
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members = [
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"example-service",
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"tarpc",
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"plugins",
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]
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[profile.dev]
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split-debuginfo = "unpacked"
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