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49 lines
1.9 KiB
Markdown
49 lines
1.9 KiB
Markdown
#### How to view collected traces
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##### Prerequisites:
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- [Docker](https://www.docker.com/get-started) (For Jaeger image)
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- [Go](https://golang.org/) 1.11+ (For execution traces collected by pprof)
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##### Using Jaeger
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Tracing is disabled by default, to enable, you can use the option `--enable-tracing`.
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Jaeger endpoint can be configured with the `--tracing-endpoint` option and defaults to `http://127.0.0.1:14268`.
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Run Jaeger:
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```sh
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$ docker run -d --name jaeger -e COLLECTOR_ZIPKIN_HTTP_PORT=9411 -p 5775:5775/udp -p 6831:6831/udp -p 6832:6832/udp -p 5778:5778 -p 16686:16686 -p 14268:14268 -p 9411:9411 jaegertracing/all-in-one:1.6
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```
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This will start the UI at `http://localhost:16686`
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##### Using the Go tool
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Tracing is disabled by default, to enable, you can use the option `--enable-tracing`.
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Run the application using the `--pprof` option to enable pprof (for trace collection).
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To collect traces for 5 seconds:
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```sh
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$ curl http://localhost:6060/debug/pprof/trace?seconds=5 -o trace.out
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```
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View the trace with:
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```sh
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$ go tool trace trace.out
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2018/05/04 10:39:59 Parsing trace...
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2018/05/04 10:39:59 Splitting trace...
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2018/05/04 10:39:59 Opening browser. Trace viewer is listening on http://127.0.0.1:51803
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```
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#### How to collect additional traces
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We use the OpenCensus library to create traces. To trace the execution of a p2p
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message through the system, we must define [spans](https://godoc.org/go.opencensus.io/trace#Span) around the code that handles the message. To correlate the trace with other spans defined for the same message, use the context passed inside the [Message](https://godoc.org/github.com/prysmaticlabs/prysm/shared/deprecated-p2p#Message) struct to create a span:
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```go
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var msg p2p.Message
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var mySpan *trace.Span
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msg.Ctx, mySpan = trace.StartSpan(msg.Ctx, "myOperation")
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myOperation()
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mySpan.End()
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```
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Another example on how to define spans can be found here: https://godoc.org/go.opencensus.io/trace#example-StartSpan
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