introduce performance profiling doc (#167)

Signed-off-by: Per Goncalves da Silva <[email protected]>

Author: awgreene

content/en/docs/advanced-tasks/performance-profiling.md

@@ -0,0 +1,96 @@
+---
+title: "OLM Performance Profiling Instrumentation"
+weight: 10
+description: >
+  The goal of this document is to familiarize you with the steps to enable and review OLM's performance profiling instrumentation.
+---
+
+## Prerequisites 
+
+- [go](https://golang.org/dl/)
+
+## Background
+
+OLM utilizes the [pprof package](https://golang.org/pkg/net/http/pprof/) from the standard go library to expose performance profiles for the OLM and Catalog Operator. 
+
+Due to the sensitive nature of profiling data, the profiling endpoints will reject any clients that do not present a verifiable certificate. Both operators must be configured with a serving certificate and a client CA bundle in order to access the profiling endpoints.
+
+This document will dive into the steps to [enable olm performance profiling](#enabling-performance-profiling) and retrieving pprof data from each component.
+
+## Enabling Performance Profiling
+
+### Creating a Certificate
+
+A valid server certificate must be created for each component before the Performance Profiling functionality can be enabled. If you are unfamiliar with certificate generation, we recommend using the [OpenSSL](https://www.openssl.org/) tool-kit and refer to the [request certificate](https://www.openssl.org/docs/man1.1.1/man1/openssl-req.html) documentation.
+
+Once you have generated a private and public key, this data should be stored in a `TLS Secret`:
+
+```bash
+$ export PRIVATE_KEY_FILENAME=private.key # Replace with the name of the file that contains the private key you generated.
+$ export PUBLIC_KEY_FILENAME=certificate.crt # Replace with the name of the file that contains the public key you generated.
+
+$ kubectl -n my-namespace create secret tls my-name --cert=$PUBLIC_KEY_FILENAME --key=$PRIVATE_KEY_FILENAME
+```
+
+### Updating OLM to Use the TLS Secret
+
+Patch the OLM or Catalog Deployment's pod template to use the generated TLS secret:
+
+- Defining a volume and volumeMount
+- Adding the `client-ca`, `tls-key` and `tls-cert` arguments
+- Replacing all mentions of port `8080` with `8443`
+- Updating the `livenessProbe` and `readinessProbe` to use HTTPS as the scheme
+
+The steps to patch an existing OLM deployment can be seen below:
+
+```bash
+$ export TLS_SECRET=my-tls-secret
+$ export CERT_PATH=/var/run/secrets # Define where to mount the certs.
+# Set Deployment name to olm-operator or catalog-operator
+$ export DEPLOYMENT_NAME=olm-operator
+
+$ kubectl patch deployment $DEPLOYMENT_NAME -n olm --type json -p='[
+    # Mount the secret to the pod
+    {"op": "add", "path": "/spec/template/spec/volumes", "value":[{"name": '$TLS_SECRET', "secret": {"secretName": '$TLS_SECRET'}}]},
+    {"op": "add", "path": "/spec/template/spec/containers/0/volumeMounts", "value":[{"name": '$TLS_SECRET', "mountPath": '$CERT_PATH'}]},
+    
+    # Add startup arguments
+    {"op": "add", "path": "/spec/template/spec/containers/0/args/-", "value":"--client-ca"},
+    {"op": "add", "path": "/spec/template/spec/containers/0/args/-", "value":"'$CERT_PATH'/tls.crt"},
+    {"op": "add", "path": "/spec/template/spec/containers/0/args/-", "value":"--tls-key"},
+    {"op": "add", "path": "/spec/template/spec/containers/0/args/-", "value":"'$CERT_PATH'/tls.key"},
+    {"op": "add", "path": "/spec/template/spec/containers/0/args/-", "value":"--tls-cert"},
+    {"op": "add", "path": "/spec/template/spec/containers/0/args/-", "value":"'$CERT_PATH'/tls.crt"},
+    
+    # Replace port 8080 with 8443
+    {"op": "replace", "path": "/spec/template/spec/containers/0/ports/0", "value":{"containerPort": 8443}},
+    {"op": "replace", "path": "/spec/template/spec/containers/0/livenessProbe/httpGet/port", "value":8443},
+    {"op": "replace", "path": "/spec/template/spec/containers/0/readinessProbe/httpGet/port", "value":8443},
+
+    # Update livenessProbe and readinessProbe to use HTTPS
+    {"op": "replace", "path": "/spec/template/spec/containers/0/readinessProbe/httpGet/scheme", "value":"HTTPS"},
+    {"op": "replace", "path": "/spec/template/spec/containers/0/livenessProbe/httpGet/scheme", "value":"HTTPS"},
+]'
+deployment.apps/olm-operator patched
+
+```
+
+## Accessing PPROF Data
+
+You will need to be able to access OLM port, for dev purposes the following commands may prove useful:
+
+```bash
+# Set Deployment name to olm-operator or catalog-operator
+$ export DEPLOYMENT_NAME=olm-operator
+$ kubectl port-forward deployment/$DEPLOYMENT_NAME 8443:8443 -n olm
+```
+
+You can then curl the OLM `/debug/pprof` endpoint to retrieve default pprof profiles like so:
+
+```bash
+$ curl https://localhost:8443/debug/pprof/heap --cert certificate.crt --key private.key  --insecure -o olm-heap
+
+$ go tool pprof --top olm-heap
+```
+
+Please review [the official pprof documentation](https://blog.golang.org/pprof) to learn more about pprof.