cleaned up platform code

src/core/server/saved_objects/migrations/core/migrate_raw_docs.ts

@@ -44,12 +44,12 @@ export async function migrateRawDocs(
   log: SavedObjectsMigrationLogger
 ): Promise<SavedObjectsRawDoc[]> {
   const migrateDocWithoutBlocking = transformNonBlocking(migrateDoc);
-  const processesDocs = [];
+  const processedDocs = [];
   for (const raw of rawDocs) {
     if (serializer.isRawSavedObject(raw)) {
       const savedObject = serializer.rawToSavedObject(raw);
       savedObject.migrationVersion = savedObject.migrationVersion || {};
-      processesDocs.push(
+      processedDocs.push(
         serializer.savedObjectToRaw({
           references: [],
           ...(await migrateDocWithoutBlocking(savedObject)),
@@ -60,12 +60,19 @@ export async function migrateRawDocs(
         `Error: Unable to migrate the corrupt Saved Object document ${raw._id}. To prevent Kibana from performing a migration on every restart, please delete or fix this document by ensuring that the namespace and type in the document's id matches the values in the namespace and type fields.`,
         { rawDocument: raw }
       );
-      processesDocs.push(raw);
+      processedDocs.push(raw);
     }
   }
-  return processesDocs;
+  return processedDocs;
 }
 
+/**
+ * Migration transform functions are potentially CPU heavy e.g. doing decryption/encryption
+ * or (de)/serializing large JSON payloads.
+ * Executing all transforms for a batch in a synchronous loop can block the event-loop for a long time.
+ * To prevent this we use setImmediate to ensure that the event-loop can process other parallel
+ * work in between each transform.
+ */
 function transformNonBlocking(
   transform: TransformFn
 ): (doc: SavedObjectUnsanitizedDoc) => Promise<SavedObjectUnsanitizedDoc> {