From 09da9305de8ca8b75df21b280dfd084c8ae77ad2 Mon Sep 17 00:00:00 2001
From: "A.Unger" <zyxancf@gmail.com>
Date: Tue, 24 Aug 2021 13:54:05 +0200
Subject: [PATCH] add profiling docs

---
 docs/ocis/development/profiling.md | 121 +++++++++++++++++++++++++++++
 1 file changed, 121 insertions(+)
 create mode 100644 docs/ocis/development/profiling.md

diff --git a/docs/ocis/development/profiling.md b/docs/ocis/development/profiling.md
new file mode 100644
index 0000000000..c43b506313
--- /dev/null
+++ b/docs/ocis/development/profiling.md
@@ -0,0 +1,121 @@
+---
+title: "Profiling"
+date: 2021-08-24T12:32:20+01:00
+weight: 56
+geekdocRepo: https://github.com/owncloud/ocis
+geekdocEditPath: edit/master/docs/ocis/development
+geekdocFilePath: profiling.md
+---
+
+{{< toc >}}
+
+The only way to enable the profiler currently is to explicitly select which areas to collect samples for. In order to do this, the following steps have to be followed.
+
+## 1. Clone Reva
+
+`git clone github.com/cs3org/reva`
+
+## 2. Patch reva with the area that you want sampled.
+
+For the purposes of this docs let's use the WebDAV `PROPFIND` path.
+
+```diff
+diff --git a/internal/http/services/owncloud/ocdav/propfind.go b/internal/http/services/owncloud/ocdav/propfind.go
+index 0e9c99be..f271572f 100644
+--- a/internal/http/services/owncloud/ocdav/propfind.go
++++ b/internal/http/services/owncloud/ocdav/propfind.go
+@@ -32,6 +32,8 @@ import (
+        "strings"
+        "time"
+
++       _ "net/http/pprof"
++
+        userv1beta1 "github.com/cs3org/go-cs3apis/cs3/identity/user/v1beta1"
+        rpc "github.com/cs3org/go-cs3apis/cs3/rpc/v1beta1"
+        link "github.com/cs3org/go-cs3apis/cs3/sharing/link/v1beta1"
+@@ -311,6 +313,12 @@ func requiresExplicitFetching(n *xml.Name) bool {
+        return true
+ }
+
++func init() {
++       go func() {
++               http.ListenAndServe(":1234", nil)
++       }()
++}
++
+ // from https://github.com/golang/net/blob/e514e69ffb8bc3c76a71ae40de0118d794855992/webdav/xml.go#L178-L205
+ func readPropfind(r io.Reader) (pf propfindXML, status int, err error) {
+        c := countingReader{r: r}
+```
+
+The previous patch will:
+
+1. import `net/http/pprof`, which will register debug handlers in `DefaultServeMux`.
+2. define a `init()` function that starts an http server with the previously registered handlers.
+
+With everything running one should have access to http://localhost:1234/debug/pprof/
+
+## 3. Replace ocis go.mod to local reva and build a new binary
+
+```diff
+diff --git a/go.mod b/go.mod
+index 131d14d7b..9668c38e4 100644
+--- a/go.mod
++++ b/go.mod
+@@ -78,6 +78,7 @@ require (
+
+ replace (
+        github.com/crewjam/saml => github.com/crewjam/saml v0.4.5
++       github.com/cs3org/reva => path/to/your/reva
+        go.etcd.io/etcd/api/v3 => go.etcd.io/etcd/api/v3 v3.0.0-20210204162551-dae29bb719dd
+        go.etcd.io/etcd/pkg/v3 => go.etcd.io/etcd/pkg/v3 v3.0.0-20210204162551-dae29bb719dd
+ )
+```
+
+Make sure to replace `github.com/cs3org/reva => path/to/your/reva` with the correct location of your reva.
+
+## 4. Build a new ocis binary
+
+From owncloud/ocis root:
+
+```console
+$ cd ocis
+$ make clean build
+```
+
+## 5. Start oCIS server
+
+From owncloud/ocis root:
+
+```console
+$ OCIS_LOG_PRETTY=true OCIS_LOG_COLOR=true ocis/bin/ocis server
+```
+
+## 6. Run `pprof`
+
+### Install pprof
+
+If `pprof` is not installed make sure to get it; one way of installing it is using the Go tools:
+
+```console
+$ go get -u github.com/google/pprof
+```
+
+### Collecting samples
+
+Collect 30 seconds of samples:
+
+```console
+$ prof -web http://:1234/debug/pprof/profile\?seconds\=30
+```
+
+Once the collection is done a browser tab will open with the result `svg`, looking similar to this:
+
+![img](https://i.imgur.com/vo0EbcX.jpg)
+
+For references on how to interpret this graph, [continue reading here](https://github.com/google/pprof/blob/master/doc/README.md#interpreting-the-callgraph).
+
+## References
+
+- https://medium.com/swlh/go-profile-your-code-like-a-master-1505be38fdba
+- https://dave.cheney.net/