Table of contents
pprof
Golang provides a built-in profiler called pprof. It is a tool that can be used to collect CPU and memory profiles. It can be used to collect profiles from a running application and then analyze them to find the root cause of performance issues.
ColdBrew exposes /debug/pprof/ endpoint on the HTTP port that can be used to collect profiles. The endpoint is only available when the configuration option DisableDebug is set to false (which is the default behaviour).
Collecting profiles
To collect a profile, you can use the go tool pprof command. For example, to collect a CPU profile, you can run the following command:
$ go tool pprof http://localhost:9091/debug/pprof/profile
This will open an interactive shell where you can run commands to analyze the profile. For example, to see the top 10 functions that are consuming the most CPU, you can run the following command:
(pprof) top5
Showing nodes accounting for 30ms, 100% of 30ms total
Showing top 5 nodes out of 45
flat flat% sum% cum cum%
20ms 66.67% 66.67% 20ms 66.67% runtime.memclrNoHeapPointers
10ms 33.33% 100% 10ms 33.33% syscall.syscall
0 0% 100% 20ms 66.67% github.com/NYTimes/gziphandler.GzipHandlerWithOpts.func1.1
0 0% 100% 10ms 33.33% github.com/ankurs/MyApp/proto.(*mySvcClient).Echo
0 0% 100% 20ms 66.67% github.com/ankurs/MyApp/proto.RegisterMySvcHandlerClient.func3
Analyzing profiles
The go tool pprof command can be also be used analyze profiles to find the root cause of performance issues. For more information, please refer to the pprof walkthrough and the diagnostics doc.
Its recommended that you go though the pprof walkthrough to get a better understanding of how to use the pprof.
Disabling pprof endpoint
The pprof endpoint can be disabled by setting the configuration option DisableDebug or the environment variable DISABLE_DEBUG to true. This is useful if you want to disable the /debug/pprof/ endpoint in production.
Its recommended to only expose the endpoint that are used by clients, and disable the rest of the endpoints at the load balancer level by using a whitelist.
Overriding log level at request time
ColdBrew provides a way to override the log level of a request based on the request parameters. This can be useful when you want to log a request at a different log level than the default log level. For example, you can log a request at the debug log level when a debug query parameter is present in the request.
For information on this feature, please refer to the Overriding log level at request time page.