Add documentation of pprof (#4705)

Signed-off-by: uncle <[email protected]>

docs/content/en/docs-dev/faq/_index.md

@@ -61,3 +61,8 @@ You can create a new Piped key. Go to the `Piped` tab at `Settings` page, and cl
 ### 8. Is it open source?
 
 Yes, PipeCD is fully open source project with APACHE LICENSE, VERSION 2.0!!
+
+### 9. How should I investigate high CPU usage or memory usage in piped, or when OOM occurs?
+
+If you're noticing high CPU usage, memory usage, or facing OOM issues in Piped, you can use the built-in support for `pprof`, a tool for visualization and analysis of profiling data.  
+`pprof` can help you identify the parts of your application that are consuming the most resources. For more detailed information and examples of how to use `pprof` in Piped, please refer to our [Using Pprof in Piped guide](../managing-piped/using-pprof-in-piped).

docs/content/en/docs-dev/user-guide/managing-piped/using-pprof-in-piped.md

@@ -0,0 +1,47 @@
+---
+title: "Using Pprof in Piped"
+linkTitle: "Using Pprof in Piped"
+weight: 10
+description: >
+  This guide is for developers who want to use pprof for performance profiling in Piped.
+---
+
+Piped provides built-in support for pprof, a tool for visualization and analysis of profiling data. It's part of the standard Go library.
+
+In Piped, several routes are registered to serve the profiling data in a format understood by the pprof tool. Here are the routes:
+
+- `/debug/pprof/`: This route serves an index page that lists the available profiling data.
+- `/debug/pprof/profile`: This route serves CPU profiling data.
+- `/debug/pprof/trace`: This route serves execution trace data.
+
+You can access these routes to get the profiling data. For example, to get the CPU profiling data, you can access the `/debug/pprof/profile` route.  
+
+Note that using these features in a production environment may impact performance.  
+
+This document explains the basic usage of [pprof](https://pkg.go.dev/net/http/pprof) in Piped. For more detailed information or specific use cases, please refer to the official Go documentation.
+
+## How to use pprof
+
+1. Access the pprof index page
+```bash
+curl http://localhost:9085/debug/pprof/
+```
+This will return an HTML page that lists the available profiling data.
+2. Get the Cpi Profile
+```bash
+curl http://localhost:9085/debug/pprof/profile > cpu.pprof
+```
+This will save the CPU profiling data to a file named cpu.pprof. You can then analyze this data using the pprof tool:
+```bash
+go tool pprof cpu.pprof
+```
+3. Get the Execution Trace
+```bash
+curl http://localhost:9085/debug/pprof/trace > trace.out
+```
+This will save the execution trace data to a file named trace.out. You can then view this trace using the go tool trace command:
+```bash
+go tool trace trace.out
+```
+Please replace localhost:9085 with the actual address and port of your Piped's admin server.
+

docs/content/en/docs-v0.45.x/faq/_index.md

@@ -61,3 +61,8 @@ You can create a new Piped key. Go to the `Piped` tab at `Settings` page, and cl
 ### 8. Is it open source?
 
 Yes, PipeCD is fully open source project with APACHE LICENSE, VERSION 2.0!!
+
+### 9. How should I investigate high CPU usage or memory usage in piped, or when OOM occurs?
+
+If you're noticing high CPU usage, memory usage, or facing OOM issues in Piped, you can use the built-in support for `pprof`, a tool for visualization and analysis of profiling data.  
+`pprof` can help you identify the parts of your application that are consuming the most resources. For more detailed information and examples of how to use `pprof` in Piped, please refer to our [Using Pprof in Piped guide](../managing-piped/using-pprof-in-piped).

docs/content/en/docs-v0.45.x/user-guide/managing-piped/using-pprof-in-piped.md

@@ -0,0 +1,47 @@
+---
+title: "Using Pprof in Piped"
+linkTitle: "Using Pprof in Piped"
+weight: 10
+description: >
+  This guide is for developers who want to use pprof for performance profiling in Piped.
+---
+
+Piped provides built-in support for pprof, a tool for visualization and analysis of profiling data. It's part of the standard Go library.
+
+In Piped, several routes are registered to serve the profiling data in a format understood by the pprof tool. Here are the routes:
+
+- `/debug/pprof/`: This route serves an index page that lists the available profiling data.
+- `/debug/pprof/profile`: This route serves CPU profiling data.
+- `/debug/pprof/trace`: This route serves execution trace data.
+
+You can access these routes to get the profiling data. For example, to get the CPU profiling data, you can access the `/debug/pprof/profile` route.  
+
+Note that using these features in a production environment may impact performance.  
+
+This document explains the basic usage of [pprof](https://pkg.go.dev/net/http/pprof) in Piped. For more detailed information or specific use cases, please refer to the official Go documentation.
+
+## How to use pprof
+
+1. Access the pprof index page
+```bash
+curl http://localhost:9085/debug/pprof/
+```
+This will return an HTML page that lists the available profiling data.
+2. Get the Cpi Profile
+```bash
+curl http://localhost:9085/debug/pprof/profile > cpu.pprof
+```
+This will save the CPU profiling data to a file named cpu.pprof. You can then analyze this data using the pprof tool:
+```bash
+go tool pprof cpu.pprof
+```
+3. Get the Execution Trace
+```bash
+curl http://localhost:9085/debug/pprof/trace > trace.out
+```
+This will save the execution trace data to a file named trace.out. You can then view this trace using the go tool trace command:
+```bash
+go tool trace trace.out
+```
+Please replace localhost:9085 with the actual address and port of your Piped's admin server.
+