What is pprof?
- Go course
- Advanced
- Lesson 53/68
- 4 min
Learn the basics of the pprof profiling tool.
What is pprof?
pprof is Go's profiling tool that shows where a program spends its time and memory. It lets you measure instead of guess. It is added to an HTTP service with one line:
import _ "net/http/pprof"
go http.ListenAndServe("localhost:6060", nil)Then go tool pprof http://localhost:6060/debug/pprof/profile?seconds=30 takes a 30-second CPU profile.
Profile types
There are several profiles under /debug/pprof/: profile (CPU), heap (memory), goroutine (all goroutine stacks), block and mutex (waiting points), allocs (all allocations). The goroutine profile is very handy for finding leaked goroutines.
Practice Goroutine count
runtime.NumGoroutine() returns the number of running goroutines. Start three goroutines (each waiting on <-dur), print the count, then call close(dur).
Starter code
package main
import (
"fmt"
"runtime"
)
func main() {
// buraya yaz
}Sample solution
package main
import (
"fmt"
"runtime"
)
func main() {
dur := make(chan struct{})
for i := 0; i < 3; i++ {
go func() { <-dur }()
}
fmt.Println(runtime.NumGoroutine())
close(dur)
}Expected output
4
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Why bind the pprof endpoint to <code>localhost</code>?
- pprof doesn't work on other addresses
- To avoid port conflicts
- Profile data exposes internals; it shouldn't be public Correct answer
- So it runs faster
Explanation: Profiles reveal function names, stacks and hints about memory contents; taking a profile also loads the server.
2 Add pprof
import _ "net/http/____"import _ "net/http/pprof"Explanation: Importing net/http/pprof registers the /debug/pprof/ endpoints on the default mux.
3 Profile and question
| Term | Meaning |
|---|---|
profile |
Where is CPU spent? |
heap |
Where is memory held? |
goroutine |
Which goroutines exist? |
mutex |
Where is lock waiting? |