Convert legacy GCF events to CloudEvents (#285)

This commit adds express middleware to convert legacy GCF requests to the equivalent CloudEvent requests. This enables developers to leverage cloud events in functions that consume events from GCP products that don't yet produce CloudEvents.

Author: matthewrobertson

.github/workflows/conformance.yml

@@ -54,6 +54,6 @@ jobs:
       with:
         functionType: 'cloudevent'
         useBuildpacks: false
-        validateMapping: false
+        validateMapping: true
         workingDirectory: 'test/conformance'
         cmd: "'npm start -- --target=writeCloudEvent --signature-type=cloudevent'"

src/cloudevents.ts

@@ -15,6 +15,21 @@
 import * as express from 'express';
 import {CloudEventsContext} from './functions';
 
+/**
+ * Custom exception class to represent errors durring event conversions.
+ */
+export class EventConversionError extends Error {}
+
+// CloudEvent service names.
+export const CE_SERVICE = {
+  FIREBASE_AUTH: 'firebaseauth.googleapis.com',
+  FIREBASE_DB: 'firebasedatabase.googleapis.com',
+  FIREBASE: 'firebase.googleapis.com',
+  FIRESTORE: 'firestore.googleapis.com',
+  PUBSUB: 'pubsub.googleapis.com',
+  STORAGE: 'storage.googleapis.com',
+};
+
 /**
  * Checks whether the incoming request is a CloudEvents event in binary content
  * mode. This is verified by checking the presence of required headers.

src/functions.ts

@@ -44,7 +44,7 @@ export type HandlerFunction =
  * A legacy event.
  */
 export interface LegacyEvent {
-  data: object;
+  data: {[key: string]: any};
   context: CloudFunctionsContext;
 }
 
@@ -75,7 +75,7 @@ export interface CloudFunctionsContext {
   /**
    * The resource that emitted the event.
    */
-  resource?: string | object;
+  resource?: string | {[key: string]: string};
 }
 
 /**

src/middelware/ce_to_legacy_event.ts

@@ -12,47 +12,45 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 import {Request, Response, NextFunction} from 'express';
-import {isBinaryCloudEvent, getBinaryCloudEventContext} from '../cloudevents';
+import {
+  CE_SERVICE,
+  isBinaryCloudEvent,
+  getBinaryCloudEventContext,
+  EventConversionError,
+} from '../cloudevents';
 
-const CE_TO_BACKGROUND_TYPE = new Map(
-  Object.entries({
-    'google.cloud.pubsub.topic.v1.messagePublished':
-      'google.pubsub.topic.publish',
-    'google.cloud.storage.object.v1.finalized':
-      'google.storage.object.finalize',
-    'google.cloud.storage.object.v1.deleted': 'google.storage.object.delete',
-    'google.cloud.storage.object.v1.archived': 'google.storage.object.archive',
-    'google.cloud.storage.object.v1.metadataUpdated':
-      'google.storage.object.metadataUpdate',
-    'google.cloud.firestore.document.v1.written':
-      'providers/cloud.firestore/eventTypes/document.write',
-    'google.cloud.firestore.document.v1.created':
-      'providers/cloud.firestore/eventTypes/document.create',
-    'google.cloud.firestore.document.v1.updated':
-      'providers/cloud.firestore/eventTypes/document.update',
-    'google.cloud.firestore.document.v1.deleted':
-      'providers/cloud.firestore/eventTypes/document.delete',
-    'google.firebase.auth.user.v1.created':
-      'providers/firebase.auth/eventTypes/user.create',
-    'google.firebase.auth.user.v1.deleted':
-      'providers/firebase.auth/eventTypes/user.delete',
-    'google.firebase.analytics.log.v1.written':
-      'providers/google.firebase.analytics/eventTypes/event.log',
-    'google.firebase.database.document.v1.created':
-      'providers/google.firebase.database/eventTypes/ref.create',
-    'google.firebase.database.document.v1.written':
-      'providers/google.firebase.database/eventTypes/ref.write',
-    'google.firebase.database.document.v1.updated':
-      'providers/google.firebase.database/eventTypes/ref.update',
-    'google.firebase.database.document.v1.deleted':
-      'providers/google.firebase.database/eventTypes/ref.delete',
-  })
-);
-
-// CloudEvent service names.
-const FIREBASE_AUTH_CE_SERVICE = 'firebaseauth.googleapis.com';
-const PUBSUB_CE_SERVICE = 'pubsub.googleapis.com';
-const STORAGE_CE_SERVICE = 'storage.googleapis.com';
+// Maps CloudEvent types to the equivalent GCF Event type
+export const CE_TO_BACKGROUND_TYPE: {[k: string]: string} = {
+  'google.cloud.pubsub.topic.v1.messagePublished':
+    'google.pubsub.topic.publish',
+  'google.cloud.storage.object.v1.finalized': 'google.storage.object.finalize',
+  'google.cloud.storage.object.v1.deleted': 'google.storage.object.delete',
+  'google.cloud.storage.object.v1.archived': 'google.storage.object.archive',
+  'google.cloud.storage.object.v1.metadataUpdated':
+    'google.storage.object.metadataUpdate',
+  'google.cloud.firestore.document.v1.written':
+    'providers/cloud.firestore/eventTypes/document.write',
+  'google.cloud.firestore.document.v1.created':
+    'providers/cloud.firestore/eventTypes/document.create',
+  'google.cloud.firestore.document.v1.updated':
+    'providers/cloud.firestore/eventTypes/document.update',
+  'google.cloud.firestore.document.v1.deleted':
+    'providers/cloud.firestore/eventTypes/document.delete',
+  'google.firebase.auth.user.v1.created':
+    'providers/firebase.auth/eventTypes/user.create',
+  'google.firebase.auth.user.v1.deleted':
+    'providers/firebase.auth/eventTypes/user.delete',
+  'google.firebase.analytics.log.v1.written':
+    'providers/google.firebase.analytics/eventTypes/event.log',
+  'google.firebase.database.document.v1.created':
+    'providers/google.firebase.database/eventTypes/ref.create',
+  'google.firebase.database.document.v1.written':
+    'providers/google.firebase.database/eventTypes/ref.write',
+  'google.firebase.database.document.v1.updated':
+    'providers/google.firebase.database/eventTypes/ref.update',
+  'google.firebase.database.document.v1.deleted':
+    'providers/google.firebase.database/eventTypes/ref.delete',
+};
 
 const PUBSUB_MESSAGE_TYPE =
   'type.googleapis.com/google.pubsub.v1.PubsubMessage';
@@ -62,11 +60,6 @@ const PUBSUB_MESSAGE_TYPE =
  */
 const CE_SOURCE_REGEX = /\/\/([^/]+)\/(.+)/;
 
-/**
- * Costom exception class to represent errors durring event converion.
- */
-export class EventConversionError extends Error {}
-
 /**
  * Is the given request a known CloudEvent that can be converted to a legacy event.
  * @param request express request object
@@ -75,7 +68,7 @@ export class EventConversionError extends Error {}
 const isConvertableCloudEvent = (request: Request): boolean => {
   if (isBinaryCloudEvent(request)) {
     const ceType = request.header('ce-type');
-    return CE_TO_BACKGROUND_TYPE.has(ceType!);
+    return !!ceType && ceType in CE_TO_BACKGROUND_TYPE;
   }
   return false;
 };
@@ -117,7 +110,7 @@ const marshallConvertableCloudEvent = (
   let resource: string | {[key: string]: string} = `${name}/${subject}`;
 
   switch (service) {
-    case PUBSUB_CE_SERVICE:
+    case CE_SERVICE.PUBSUB:
       // PubSub resource format
       resource = {
         service: service,
@@ -129,7 +122,7 @@ const marshallConvertableCloudEvent = (
         data = data.message;
       }
       break;
-    case FIREBASE_AUTH_CE_SERVICE:
+    case CE_SERVICE.FIREBASE_AUTH:
       // FirebaseAuth resource format
       resource = name;
       if ('metadata' in data) {
@@ -144,7 +137,7 @@ const marshallConvertableCloudEvent = (
         }
       }
       break;
-    case STORAGE_CE_SERVICE:
+    case CE_SERVICE.STORAGE:
       // CloudStorage resource format
       resource = {
         name: `${name}/${subject}`,
@@ -158,7 +151,7 @@ const marshallConvertableCloudEvent = (
     context: {
       eventId: ceContext.id!,
       timestamp: ceContext.time!,
-      eventType: CE_TO_BACKGROUND_TYPE.get(ceContext.type!),
+      eventType: CE_TO_BACKGROUND_TYPE[ceContext.type!],
       resource,
     },
     data,