Cache the OpenAPI schema. (#833)

For large programs, re-fetching this schema repeatedly adds up to a
significant portion of execution time. This caching reduces the
execution time of the Istio example by about 60-70%.

Contributes to #827.

CHANGELOG.md

@@ -8,6 +8,7 @@
 
 ### Improvements
 
+-   Cache the OpenAPI schema to improve performance. (https://github.com/pulumi/pulumi-kubernetes/pull/833).
 -   Aggregate error messages from Pods on Job Read. (https://github.com/pulumi/pulumi-kubernetes/pull/831).
 -   Improve interactive status for Jobs. (https://github.com/pulumi/pulumi-kubernetes/pull/832).
 

pkg/clients/memcache.go

@@ -21,6 +21,9 @@ limitations under the License.
 // mechanism, and causes unactionable error messages to appear in the CLI.
 // This error logging was disabled.
 //
+// Additionally, we improved caching of the OpenAPI schema in the OpenAPISchema method.
+// If this change merges upstream, we will reconcile those changes in a future release.
+//
 // [1] https://github.com/kubernetes/client-go/blob/2dda7ceeec102b5a60e2abf37758642118501910/discovery/cached/memcache.go
 
 package clients
@@ -56,6 +59,7 @@ type memCacheClient struct {
 	delegate discovery.DiscoveryInterface
 
 	lock                   sync.RWMutex
+	schema                 *openapi_v2.Document
 	groupToServerResources map[string]*cacheEntry
 	groupList              *metav1.APIGroupList
 	cacheValid             bool
@@ -159,7 +163,18 @@ func (d *memCacheClient) ServerVersion() (*version.Info, error) {
 }
 
 func (d *memCacheClient) OpenAPISchema() (*openapi_v2.Document, error) {
-	return d.delegate.OpenAPISchema()
+	d.lock.Lock()
+	defer d.lock.Unlock()
+
+	if d.schema == nil {
+		sch, err := d.delegate.OpenAPISchema()
+		if err != nil {
+			return nil, err
+		}
+		d.schema = sch
+	}
+
+	return d.schema, nil
 }
 
 func (d *memCacheClient) Fresh() bool {
@@ -179,6 +194,7 @@ func (d *memCacheClient) Invalidate() {
 	d.cacheValid = false
 	d.groupToServerResources = nil
 	d.groupList = nil
+	d.schema = nil
 }
 
 // refreshLocked refreshes the state of cache. The caller must hold d.lock for