fix(plugins/plugin-kubectl): cache kind canonicalization lookup

Fixes #4489

plugins/plugin-kubectl/src/controller/kubectl/explain.ts

@@ -1,5 +1,5 @@
 /*
- * Copyright 2019 IBM Corporation
+ * Copyright 2019-2020 IBM Corporation
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -50,7 +50,7 @@ ${formatDocumentation(_[4])}
   }
 }
 
-// alternate patterns to match against
+/** alternate patterns to match against */
 const kvd = /^KIND:\s+(\S+)\nVERSION:\s+(\S+)\n\nDESCRIPTION:\n(\s*DEPRECATED - )?([\s\S]+)/
 const kvdf = /^KIND:\s+(\S+)\nVERSION:\s+(\S+)\n\nDESCRIPTION:\n(\s*DEPRECATED - )?([\s\S]+)\n\nFIELDS:\n([\s\S]+)/
 
@@ -127,22 +127,38 @@ ${isDeprecated ? `### Warnings\n${strings('This API Resource is deprecated')}` :
     return response
   }
 
+/**
+ * Cache of the getKind() lookup
+ *
+ */
+const cache: Record<string, Promise<string>> = {}
+
 /**
  * @param kindAsProvidedByUser e.g. pod or po
  * @return e.g. Pod
  *
  */
 export async function getKind(command: string, args: Arguments, kindAsProvidedByUser: string): Promise<string> {
-  try {
-    const ourArgs = Object.assign({}, args, { command: `kubectl explain ${kindAsProvidedByUser}` })
-    const explained = await doExecWithStdout(ourArgs, undefined, command)
-
-    return explained.match(/^KIND:\s+(.*)/)[1]
-  } catch (err) {
-    if (!/does not exist/i.test(err.message)) {
-      console.error(`error explaining kind ${kindAsProvidedByUser}`, err)
-    }
+  if (!cache[kindAsProvidedByUser]) {
+    // otherwise, we need to do a more expensive call to `kubectl`
+    // eslint-disable-next-line no-async-promise-executor
+    cache[kindAsProvidedByUser] = new Promise<string>(async (resolve, reject) => {
+      try {
+        const ourArgs = Object.assign({}, args, { command: `${command} explain ${kindAsProvidedByUser}` })
+        const explained = await doExecWithStdout(ourArgs, undefined, command)
+
+        const kindFromServer = explained.match(/^KIND:\s+(.*)/)[1]
+        resolve(kindFromServer)
+      } catch (err) {
+        if (!/does not exist/i.test(err.message)) {
+          console.error(`error explaining kind ${kindAsProvidedByUser}`, err)
+          reject(err)
+        }
+      }
+    })
   }
+
+  return cache[kindAsProvidedByUser]
 }
 
 export default (registrar: Registrar) => {