fix: handle firehose subscription error reconnect (Close #44) (#46)

.env.example

@@ -20,3 +20,6 @@ FEEDGEN_PUBLISHER_DID="did:plc:abcde...."
 
 # Only use this if you want a service did different from did:web
 # FEEDGEN_SERVICE_DID="did:plc:abcde..."
+
+# Delay between reconnect attempts to the firehose subscription endpoint (in milliseconds)
+FEEDGEN_SUBSCRIPTION_RECONNECT_DELAY=3000

src/config.ts

@@ -15,4 +15,5 @@ export type Config = {
   subscriptionEndpoint: string
   serviceDid: string
   publisherDid: string
+  subscriptionReconnectDelay: number
 }

src/index.ts

@@ -15,6 +15,8 @@ const run = async () => {
       'wss://bsky.social',
     publisherDid:
       maybeStr(process.env.FEEDGEN_PUBLISHER_DID) ?? 'did:example:alice',
+    subscriptionReconnectDelay:
+      maybeInt(process.env.FEEDGEN_SUBSCRIPTION_RECONNECT_DELAY) ?? 3000,
     hostname,
     serviceDid,
   })

src/server.ts

@@ -63,7 +63,7 @@ export class FeedGenerator {
 
   async start(): Promise<http.Server> {
     await migrateToLatest(this.db)
-    this.firehose.run()
+    this.firehose.run(this.cfg.subscriptionReconnectDelay)
     this.server = this.app.listen(this.cfg.port, this.cfg.listenhost)
     await events.once(this.server, 'listening')
     return this.server

src/util/subscription.ts

@@ -36,7 +36,8 @@ export abstract class FirehoseSubscriptionBase {
 
   abstract handleEvent(evt: RepoEvent): Promise<void>
 
-  async run() {
+  async run(subscriptionReconnectDelay: number) {
+    try {
       for await (const evt of this.sub) {
         try {
           await this.handleEvent(evt)
@@ -48,6 +49,10 @@ export abstract class FirehoseSubscriptionBase {
           await this.updateCursor(evt.seq)
         }
       }
+    } catch (err) {
+      console.error('repo subscription errored', err)
+      setTimeout(() => this.run(subscriptionReconnectDelay), subscriptionReconnectDelay)
+    }
   }
 
   async updateCursor(cursor: number) {