wu-sheng opened a new pull request #2: Finish the tracing core APIs URL: https://github.com/apache/skywalking-rust/pull/2 # Concepts All concepts are from the official SkyWalking definitions. ## Span Span is an important and common concept in distributed tracing system. Learn Span from Google Dapper Paper. For better performance, we extend the span into 3 kinds. 1. EntrySpan EntrySpan represents a service provider, also the endpoint of server side. As an APM system, we are targeting the application servers. So almost all the services and MQ-consumer are EntrySpan(s). 2. LocalSpan LocalSpan represents a normal Java method, which does not relate to remote service, neither a MQ producer/consumer nor a service(e.g. HTTP service) provider/consumer. 3. ExitSpan ExitSpan represents a client of service or MQ-producer, as named as LeafSpan at early age of SkyWalking. e.g. accessing DB by JDBC, reading Redis/Memcached are cataloged an ExitSpan. Tag and Log are similar attributes of the span. - Tag is a key:value pair to indicate the attribute with a string value. - Log is heavier than tag, with one timestamp and multiple key:value pairs. Log represents an event, typically an error happens. ## TracingContext TracingContext is the context of the tracing process. Span should only be created through context, and be archived into the context after the span finished. ## Injectable Injectable is used(optional) when the exit span creates. This Injectable received the notification from tracing context, including the key and value for tracing context across process propagation. Typically, Injectable implementation would manipulate the RPC header/metadata to make the key/value sent to the server side. ## Extractable Extractable is used(optional) when the entry span creates. The Extractable fetches the value of the given key from the propagated context. Typically, Extractable implementation would read the RPC header/metadata, which sent from the client side. # APIs ## Tracing Core APIs Tracing core APIs are 100% manual control tracing APIs. Users could use them to trace any process by following SkyWalking core concepts. ```rust let mut context = TracingContext::new(&reporter).unwrap(); let span1 = context.create_entry_span("op1", None, Some(&MockerHeader {})); { assert_eq!(span1.span_id(), 0); let mut span2 = context.create_local_span("op2", Some(&span1)); span2.tag(Tag::new(String::from("tag1"), String::from("value1"))); { assert_eq!(span2.span_id(), 1); let mut span3 = context.create_exit_span("op3", Some(&span2), "127.0.0.1:8080", Some(&HeaderCarrier {})); assert_eq!(span3.span_id(), 2); context.finish_span(span3); } context.finish_span(span2); } context.finish_span(span1); reporter.report_trace(context); ``` --- Notice, report module has not finished. Report module monitors the tracing context finish event and do 1. Service and service instance register 1. Trace report
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