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Retrieving Debug Information

Each Dgraph data node exposes profile over /debug/pprof endpoint and metrics over /debug/vars endpoint. Each Dgraph data node has it’s own profiling and metrics information. Below is a list of debugging information exposed by Dgraph and the corresponding commands to retrieve them.

Metrics Information

If you are collecting these metrics from outside the Dgraph instance you need to pass --expose_trace=true flag, otherwise there metrics can be collected by connecting to the instance over localhost.

curl http://<IP>:<HTTP_PORT>/debug/vars

Metrics can also be retrieved in the Prometheus format at /debug/prometheus_metrics. See the Metrics section for the full list of metrics.

Profiling Information

Profiling information is available via the go tool pprof profiling tool built into Go. The “Profiling Go programs” Go blog post will help you get started with using pprof. Each Dgraph Zero and Dgraph Alpha exposes a debug endpoint at /debug/pprof/<profile> via the HTTP port.

go tool pprof http://<IP>:<HTTP_PORT>/debug/pprof/heap
Fetching profile from ...
Saved Profile in ...

The output of the command would show the location where the profile is stored.

In the interactive pprof shell, you can use commands like top to get a listing of the top functions in the profile, web to get a visual graph of the profile opened in a web browser, or list to display a code listing with profiling information overlaid.

CPU Profile

go tool pprof http://<IP>:<HTTP_PORT>/debug/pprof/profile

Memory Profile

go tool pprof http://<IP>:<HTTP_PORT>/debug/pprof/heap

Block Profile

Dgraph by default doesn’t collect the block profile. Dgraph must be started with --profile_mode=block and --block_rate=<N> with N > 1.

go tool pprof http://<IP>:<HTTP_PORT>/debug/pprof/block

Goroutine stack

The HTTP page /debug/pprof/ is available at the HTTP port of a Dgraph Zero or Dgraph Alpha. From this page a link to the “full goroutine stack dump” is available (e.g., on a Dgraph Alpha this page would be at http://localhost:8080/debug/pprof/goroutine?debug=2). Looking at the full goroutine stack can be useful to understand goroutine usage at that moment.