feat(pubsub): add maxListeners to subscription eventEmitter (#688)

Author: xvaara

packages/pg-pubsub/README.md

@@ -65,6 +65,7 @@ const postgraphileOptions = {
   pluginHook,
   subscriptions: true, // Enable PostGraphile websocket capabilities
   simpleSubscriptions: true, // Add the `listen` subscription field
+  subscriptionEventEmitterMaxListeners: 20, // Set max listeners on eventEmitter, 0 unlimited, 10 default
   websocketMiddlewares: [
     // Add whatever middlewares you need here, note that they should only
     // manipulate properties on req/res, they must not sent response data. e.g.:

packages/pg-pubsub/src/index.ts

@@ -13,6 +13,7 @@ declare module "postgraphile" {
   interface PostGraphileOptions {
     simpleSubscriptions?: boolean;
     subscriptionAuthorizationFunction?: string;
+    subscriptionEventEmitterMaxListeners?: number;
   }
 }
 
@@ -56,6 +57,11 @@ const plugin: PostGraphilePlugin = {
 
   ["postgraphile:options"](incomingOptions, { pgPool }) {
     const eventEmitter = new EventEmitter();
+    if (incomingOptions.subscriptionEventEmitterMaxListeners != null) {
+      eventEmitter.setMaxListeners(
+        incomingOptions.subscriptionEventEmitterMaxListeners
+      );
+    }
     const {
       simpleSubscriptions,
       subscriptionAuthorizationFunction,