chore: more docstrings (#606)

Signed-off-by: Michael Crenshaw <[email protected]>

pkg/cache/cluster.go

@@ -69,7 +69,9 @@ const (
 )
 
 type apiMeta struct {
-	namespaced  bool
+	namespaced bool
+	// watchCancel stops the watch of all resources for this API. This gets called when the cache is invalidated or when
+	// the watched API ceases to exist (e.g. a CRD gets deleted).
 	watchCancel context.CancelFunc
 }
 
@@ -468,7 +470,7 @@ func (c *clusterCache) stopWatching(gk schema.GroupKind, ns string) {
 	}
 }
 
-// startMissingWatches lists supported cluster resources and start watching for changes unless watch is already running
+// startMissingWatches lists supported cluster resources and starts watching for changes unless watch is already running
 func (c *clusterCache) startMissingWatches() error {
 	apis, err := c.kubectl.GetAPIResources(c.config, true, c.settings.ResourcesFilter)
 	if err != nil {
@@ -570,6 +572,7 @@ func (c *clusterCache) listResources(ctx context.Context, resClient dynamic.Reso
 	return resourceVersion, callback(listPager)
 }
 
+// loadInitialState loads the state of all the resources retrieved by the given resource client.
 func (c *clusterCache) loadInitialState(ctx context.Context, api kube.APIResourceInfo, resClient dynamic.ResourceInterface, ns string, lock bool) (string, error) {
 	var items []*Resource
 	resourceVersion, err := c.listResources(ctx, resClient, func(listPager *pager.ListPager) error {
@@ -728,6 +731,9 @@ func (c *clusterCache) watchEvents(ctx context.Context, api kube.APIResourceInfo
 	})
 }
 
+// processApi processes all the resources for a given API. First we construct an API client for the given API. Then we
+// call the callback. If we're managing the whole cluster, we call the callback with the client and an empty namespace.
+// If we're managing specific namespaces, we call the callback for each namespace.
 func (c *clusterCache) processApi(client dynamic.Interface, api kube.APIResourceInfo, callback func(resClient dynamic.ResourceInterface, ns string) error) error {
 	resClient := client.Resource(api.GroupVersionResource)
 	switch {
@@ -797,6 +803,17 @@ func (c *clusterCache) checkPermission(ctx context.Context, reviewInterface auth
 	return true, nil
 }
 
+// sync retrieves the current state of the cluster and stores relevant information in the clusterCache fields.
+//
+// First we get some metadata from the cluster, like the server version, OpenAPI document, and the list of all API
+// resources.
+//
+// Then we get a list of the preferred versions of all API resources which are to be monitored (it's possible to exclude
+// resources from monitoring). We loop through those APIs asynchronously and for each API we list all resources. We also
+// kick off a goroutine to watch the resources for that API and update the cache constantly.
+//
+// When this function exits, the cluster cache is up to date, and the appropriate resources are being watched for
+// changes.
 func (c *clusterCache) sync() error {
 	c.log.Info("Start syncing cluster")
 
@@ -843,6 +860,8 @@ func (c *clusterCache) sync() error {
 	if err != nil {
 		return err
 	}
+
+	// Each API is processed in parallel, so we need to take out a lock when we update clusterCache fields.
 	lock := sync.Mutex{}
 	err = kube.RunAllAsync(len(apis), func(i int) error {
 		api := apis[i]