[release/v1.2] Add doc about profiling Alloy (#1840)

Co-authored-by: Clayton Cornell <[email protected]>
Co-authored-by: Paulin Todev <[email protected]>

docs/sources/troubleshoot/profile.md

@@ -0,0 +1,101 @@
+---
+canonical: https://grafana.com/docs/alloy/latest/troubleshoot/profile/
+description: Learn how to profile resource consumption
+title: Profile Grafana Alloy resource consumption
+menuTitle: Profile resource consumption
+weight: 300
+---
+
+# Profile {{% param "FULL_PRODUCT_NAME" %}} resource consumption
+
+{{< param "PRODUCT_NAME" >}} is written in the Go programming language, which offers [built-in][pprof-pkg] support for profiling.
+Like other applications written in Go, you can profile {{< param "PRODUCT_NAME" >}} by sending an HTTP request, which returns a pprof Go profile.
+
+Once you have the pprof file, visualize it as a [flame graph][flame-graph] in [Grafana Pyroscope][pyroscope-getstarted].
+Alternatively, you could visualize it on [Grafana Play][pyroscope-adhoc] or locally by using Go's built-in [pprof tool][go-pprof].
+
+{{< admonition type="note" >}}
+A profile may contain sensitive information about your environment.
+You may not want to upload your profiles to a public location.
+{{< /admonition >}}
+
+The port you use to send the HTTP request is controlled by the `--server.http.listen-addr` [command line argument][cmd-cli].
+It is set to `127.0.0.1:12345` by default.
+
+[pprof-pkg]: https://pkg.go.dev/net/http/pprof
+[pyroscope-adhoc]: https://play.grafana.org/a/grafana-pyroscope-app/ad-hoc
+[go-pprof]: https://go.dev/blog/pprof
+[pyroscope-getstarted]: https://grafana.com/docs/pyroscope/latest/get-started/
+[flame-graph]: https://grafana.com/docs/pyroscope/latest/view-and-analyze-profile-data/flamegraphs/
+[cmd-cli]: ../../reference/cli/run
+
+## Obtaining a single profile
+
+Different types of HTTP requests will retrieve different profiles.
+
+### Memory consumption
+
+Goroutine leaks often cause memory leaks. 
+This is why obtaining a goroutine profile is usually necessary when investigating memory issues.
+For example:
+
+```bash
+curl localhost:12345/debug/pprof/heap -o heap.pprof
+curl localhost:12345/debug/pprof/goroutine -o goroutine.pprof
+```
+
+It is often helpful to collect profiles both when memory usage is low and when it is high.
+You can compare the profiles, and it may be easier to identify what caused the memory consumption to increase.
+
+### CPU consumption
+
+If you are experiencing high CPU consumption, you can collect a CPU profile:
+
+```bash
+curl http://localhost:12345/debug/pprof/profile?seconds=30 -o cpu.pprof
+```
+
+The `?seconds=30` part of the URL above means the profiling will continue for 30 seconds.
+
+## Continuous profiling
+
+You don't have to send manual `curl` commands each time you want to collect profiles.
+You can also profile continuously using the [pyroscope components][] in {{< param "PRODUCT_NAME" >}}.
+
+If you have very few {{< param "PRODUCT_NAME" >}} instances, you can even configure them to profile themselves.
+However, if you have a large cluster of collectors, it is best to set up {{< param "PRODUCT_NAME" >}} instances whose sole job is to profile other {{< param "PRODUCT_NAME" >}} instances.
+
+The following is an example of an {{< param "PRODUCT_NAME" >}} instance profiling itself:
+
+```alloy
+pyroscope.scrape "default" {
+  targets    = [{"__address__" = "localhost:12345", "service_name"="alloy"}]
+  forward_to = [pyroscope.write.default.receiver]
+}
+
+pyroscope.write "default" {
+  endpoint {
+    url = "https://profiles-prod-014.grafana.net"
+    basic_auth {
+      username = sys.env("PYROSCOPE_USERNAME")
+      password = sys.env("PYROSCOPE_PASSWORD")
+    }
+  }
+}
+```
+
+[pyroscope components]: ../../reference/components/pyroscope
+
+## Expected resource consumption
+
+Refer to [Estimate resource usage][res-usage] for more information about the expected resource consumption in {{< param "PRODUCT_NAME" >}}.
+
+[res-usage]: ../../introduction/estimate-resource-usage
+
+## {{% param "PRODUCT_NAME" %}} consumes an abnormally large amount of resources
+
+If {{< param "PRODUCT_NAME" >}} consumes an abnormally large amount of resources, you can open an issue in the [Alloy repository][alloy-repo]. 
+Attach your pprof files and your {{< param "PRODUCT_NAME" >}} configuration file.
+Make sure you redact any secrets in the attachments.
+
+[alloy-repo]: https://github.com/grafana/alloy/issues