feat: added the ability to disable catalog processing

Signed-off-by: blam <ben@blam.sh>

plugins/catalog-backend/config.d.ts

@@ -164,7 +164,6 @@ export interface Config {
 
     /**
      * The interval at which the catalog should process its entities.
-     *
      * @remarks
      *
      * Example:
@@ -186,5 +185,20 @@ export interface Config {
      * housing catalog-info files.
      */
     processingInterval?: HumanDuration;
+    /**
+     * If the processing engine should be started or not, defaults to true.
+     * @remarks
+     *
+     * Example:
+     *
+     * ```yaml
+     * catalog:
+     *   processingInterval: false
+     * ```
+     *
+     * This will enable or disable the processing of entities in the Catalog. This can be useful
+     * to use with Read Replica deployments of the catalog.
+     */
+    processingEnabled?: boolean;
   };
 }

plugins/catalog-backend/src/service/CatalogPlugin.ts

@@ -42,6 +42,7 @@ import {
 import { merge } from 'lodash';
 import { Permission } from '@backstage/plugin-permission-common';
 import { ForwardedError } from '@backstage/errors';
+import { constrainedMemory } from 'node:process';
 
 class CatalogLocationsExtensionPointImpl
   implements CatalogLocationsExtensionPoint
@@ -301,10 +302,13 @@ export const catalogPlugin = createBackendPlugin({
 
         const { processingEngine, router } = await builder.build();
 
-        lifecycle.addStartupHook(async () => {
-          await processingEngine.start();
-        });
-        lifecycle.addShutdownHook(() => processingEngine.stop());
+        if (config.getOptionalBoolean('catalog.processingEnabled') ?? true) {
+          lifecycle.addStartupHook(async () => {
+            await processingEngine.start();
+          });
+          lifecycle.addShutdownHook(() => processingEngine.stop());
+        }
+
         httpRouter.use(router);
       },
     });