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rc: enable go profiling by default on the --rc port

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This means you can use the pprof tool on a running rclone, eg

    go tool pprof http://localhost:5572/debug/pprof/heap
This commit is contained in:
Nick Craig-Wood 2018-05-11 11:12:58 +01:00
parent 7bf2d389a8
commit 573ef4c8ee
2 changed files with 47 additions and 0 deletions
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46
docs/content/rc.md
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@ -271,3 +271,49 @@ curl -H "Content-Type: application/json" -X POST -d '{"potato":2,"sausage":1}' '
"sausage": 1
}
```
## Debugging rclone with pprof ##
If you use the `--rc` flag this will also enable the use of the go
profiling tools on the same port.
To use these, first [install go](https://golang.org/doc/install).
Then (for example) to profile rclone's memory use you can run:
go tool pprof -web http://localhost:5572/debug/pprof/heap
This should open a page in your browser showing what is using what
memory.
You can also use the `-text` flag to produce a textual summary
```
$ go tool pprof -text http://localhost:5572/debug/pprof/heap
Showing nodes accounting for 1537.03kB, 100% of 1537.03kB total
flat flat% sum% cum cum%
1024.03kB 66.62% 66.62% 1024.03kB 66.62% github.com/ncw/rclone/vendor/golang.org/x/net/http2/hpack.addDecoderNode
513kB 33.38% 100% 513kB 33.38% net/http.newBufioWriterSize
0 0% 100% 1024.03kB 66.62% github.com/ncw/rclone/cmd/all.init
0 0% 100% 1024.03kB 66.62% github.com/ncw/rclone/cmd/serve.init
0 0% 100% 1024.03kB 66.62% github.com/ncw/rclone/cmd/serve/restic.init
0 0% 100% 1024.03kB 66.62% github.com/ncw/rclone/vendor/golang.org/x/net/http2.init
0 0% 100% 1024.03kB 66.62% github.com/ncw/rclone/vendor/golang.org/x/net/http2/hpack.init
0 0% 100% 1024.03kB 66.62% github.com/ncw/rclone/vendor/golang.org/x/net/http2/hpack.init.0
0 0% 100% 1024.03kB 66.62% main.init
0 0% 100% 513kB 33.38% net/http.(*conn).readRequest
0 0% 100% 513kB 33.38% net/http.(*conn).serve
0 0% 100% 1024.03kB 66.62% runtime.main
```
Possible profiles to look at:
* Memory: `go tool pprof http://localhost:5572/debug/pprof/heap`
* 30-second CPU profile: `go tool pprof http://localhost:5572/debug/pprof/profile`
* 5-second execution trace: `wget http://localhost:5572/debug/pprof/trace?seconds=5`
See the [net/http/pprof docs](https://golang.org/pkg/net/http/pprof/)
for more info on how to use the profiling and for a general overview
see [the Go team's blog post on profiling go programs](https://blog.golang.org/profiling-go-programs).
The profiling hook is [zero overhead unless it is used](https://stackoverflow.com/q/26545159/164234).

1
fs/rc/rc.go
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@ -11,6 +11,7 @@ import (
"encoding/json"
"io"
"net/http"
_ "net/http/pprof" // install the pprof http handlers
"strings"
"github.com/ncw/rclone/cmd/serve/httplib"