Expose Linode Client Prometheus metrics

Add `--authorization-always-allow-paths="/metrics"` to command line to
allow scraping these metrics.

In addition to Linode Client metrics, standard controller and worqueue
metrics are visible by default.

To disambiguate CCM node controller work queue name, it's explicitly
named "ccm_node". That is, "node", "service" are upstream work
queues of k8s cloud-provider service controller and "ccm_node" is
the work queue of Linode CCM node controller.

Fixes #296

Author: rsienko

README.md

@@ -367,6 +367,16 @@ Values can be set/overrided by using the '--set var=value,...' flag or by passin
 
 Recommendation: Use custom-values.yaml to override the variables to avoid any errors with template rendering
 
+### Prometheus metrics
+
+Cloud Controller Manager exposes metrics by default on port given by
+`--secure-port` flag. The endpoint is protected from unauthenticated access by
+default.  To allow unauthenticated clients (`system:anonymous`) access
+Prometheus metrics, use `--authorization-always-allow-paths="/metrics"` command
+line flag.
+
+Linode API calls can be monitored using `ccm_linode_client_requests_total` metric.
+
 ### Upstream Documentation Including Deployment Instructions
 
 [Kubernetes Cloud Controller Manager](https://kubernetes.io/docs/tasks/administer-cluster/running-cloud-controller/).

cloud/linode/client/client.go

@@ -1,6 +1,7 @@
 package client
 
 //go:generate go run github.com/golang/mock/mockgen -destination mocks/mock_client.go -package mocks github.com/linode/linode-cloud-controller-manager/cloud/linode/client Client
+//go:generate go run github.com/hexdigest/gowrap/cmd/gowrap gen -g -p github.com/linode/linode-cloud-controller-manager/cloud/linode/client -i Client -t ../../../hack/templates/prometheus.go.gotpl -o client_with_metrics.go -l ""
 
 import (
 	"context"
@@ -9,6 +10,7 @@ import (
 	"os"
 	"time"
 
+	_ "github.com/hexdigest/gowrap"
 	"github.com/linode/linodego"
 	"k8s.io/klog/v2"
 )