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Tracing
Lotus uses OpenCensus for tracing application flow. This generates spans through the execution of annotated code paths.
Currently it is set up to use jaeger, though other tracing backends should be fairly easy to swap in.
Running Locally
To easily run and view tracing locally, first, install jaeger. The easiest way
to do this is to download the binaries from
https://www.jaegertracing.io/download/ and then run the jaeger-all-in-one
binary. This will start up jaeger, listen for spans on localhost:6831, and
expose a web UI for viewing traces on http://localhost:16686/.
Now, to start sending traces from lotus to jaeger, set the environment variable
LOTUS_JAEGER to localhost:6831, and start the lotus daemon.
Now, to view any generated traces, open up http://localhost:16686/ in your
browser.
Adding Spans
To annotate a new codepath with spans, add the following lines to the top of the function you wish to trace:
ctx, span := trace.StartSpan(ctx, "put function name here")
defer span.End()