Reconnect with exponential backoff flag: enableReconnect

README.md

@@ -133,14 +133,44 @@ import WebSocket from 'ws'
 useWebSocketImplementation(WebSocket)
 ```
 
-You can enable regular pings of connected relays with the `enablePing` option. This will set up a heartbeat that closes the websocket if it doesn't receive a response in time. Some platforms don't report websocket disconnections due to network issues, and enabling this can increase reliability.
+#### enablePing
+
+You can enable regular pings of connected relays with the `enablePing` option. This will set up a heartbeat that closes the websocket if it doesn't receive a response in time. Some platforms, like Node.js, don't report websocket disconnections due to network issues, and enabling this can increase the reliability of the `onclose` event.
 
 ```js
 import { SimplePool } from 'nostr-tools/pool'
 
 const pool = new SimplePool({ enablePing: true })
 ```
 
+#### enableReconnect
+
+You can also enable automatic reconnection with the `enableReconnect` option. This will make the pool try to reconnect to relays with an exponential backoff delay if the connection is lost unexpectedly.
+
+```js
+import { SimplePool } from 'nostr-tools/pool'
+
+const pool = new SimplePool({ enableReconnect: true })
+```
+
+Using both `enablePing: true` and `enableReconnect: true` is recommended as it will improve the reliability and timeliness of the reconnection (at the expense of slighly higher bandwidth due to the ping messages).
+
+```js
+// on Node.js
+const pool = new SimplePool({ enablePing: true, enableReconnect: true })
+```
+
+The `enableReconnect` option can also be a callback function which will receive the current subscription filters and should return a new set of filters. This is useful if you want to modify the subscription on reconnect, for example, to update the `since` parameter to fetch only new events.
+
+```js
+const pool = new SimplePool({
+  enableReconnect: (filters) => {
+    const newSince = Math.floor(Date.now() / 1000)
+    return filters.map(filter => ({ ...filter, since: newSince }))
+  }
+})
+```
+
 ### Parsing references (mentions) from a content based on NIP-27
 
 ```js

abstract-pool.ts

@@ -33,6 +33,7 @@ export class AbstractSimplePool {
 
   public verifyEvent: Nostr['verifyEvent']
   public enablePing: boolean | undefined
+  public enableReconnect: boolean | ((filters: Filter[]) => Filter[]) | undefined
   public trustedRelayURLs: Set<string> = new Set()
 
   private _WebSocket?: typeof WebSocket
@@ -41,6 +42,7 @@ export class AbstractSimplePool {
     this.verifyEvent = opts.verifyEvent
     this._WebSocket = opts.websocketImplementation
     this.enablePing = opts.enablePing
+    this.enableReconnect = opts.enableReconnect
   }
 
   async ensureRelay(url: string, params?: { connectionTimeout?: number }): Promise<AbstractRelay> {
@@ -52,9 +54,12 @@ export class AbstractSimplePool {
         verifyEvent: this.trustedRelayURLs.has(url) ? alwaysTrue : this.verifyEvent,
         websocketImplementation: this._WebSocket,
         enablePing: this.enablePing,
+        enableReconnect: this.enableReconnect,
       })
       relay.onclose = () => {
-        this.relays.delete(url)
+        if (relay && !relay.enableReconnect) {
+          this.relays.delete(url)
+        }
       }
       if (params?.connectionTimeout) relay.connectionTimeout = params.connectionTimeout
       this.relays.set(url, relay)

abstract-relay.ts

@@ -16,6 +16,7 @@ export type AbstractRelayConstructorOptions = {
   verifyEvent: Nostr['verifyEvent']
   websocketImplementation?: typeof WebSocket
   enablePing?: boolean
+  enableReconnect?: boolean | ((filters: Filter[]) => Filter[])
 }
 
 export class SendingOnClosedConnection extends Error {
@@ -37,9 +38,15 @@ export class AbstractRelay {
   public publishTimeout: number = 4400
   public pingFrequency: number = 20000
   public pingTimeout: number = 20000
+  public resubscribeBackoff: number[] = [10000, 10000, 10000, 20000, 20000, 30000, 60000]
   public openSubs: Map<string, Subscription> = new Map()
   public enablePing: boolean | undefined
+  public enableReconnect: boolean | ((filters: Filter[]) => Filter[])
   private connectionTimeoutHandle: ReturnType<typeof setTimeout> | undefined
+  private reconnectTimeoutHandle: ReturnType<typeof setTimeout> | undefined
+  private pingTimeoutHandle: ReturnType<typeof setTimeout> | undefined
+  private reconnectAttempts: number = 0
+  private closedIntentionally: boolean = false
 
   private connectionPromise: Promise<void> | undefined
   private openCountRequests = new Map<string, CountResolver>()
@@ -59,6 +66,7 @@ export class AbstractRelay {
     this.verifyEvent = opts.verifyEvent
     this._WebSocket = opts.websocketImplementation || WebSocket
     this.enablePing = opts.enablePing
+    this.enableReconnect = opts.enableReconnect || false
   }
 
   static async connect(url: string, opts: AbstractRelayConstructorOptions): Promise<AbstractRelay> {
@@ -88,6 +96,40 @@ export class AbstractRelay {
     return this._connected
   }
 
+  private async reconnect(): Promise<void> {
+    const backoff = this.resubscribeBackoff[Math.min(this.reconnectAttempts, this.resubscribeBackoff.length - 1)]
+    this.reconnectAttempts++
+
+    this.reconnectTimeoutHandle = setTimeout(async () => {
+      try {
+        await this.connect()
+      } catch (err) {
+        // this will be called again through onclose/onerror
+      }
+    }, backoff)
+  }
+
+  private handleHardClose(reason: string) {
+    if (this.pingTimeoutHandle) {
+      clearTimeout(this.pingTimeoutHandle)
+      this.pingTimeoutHandle = undefined
+    }
+
+    this._connected = false
+    this.connectionPromise = undefined
+
+    const wasIntentional = this.closedIntentionally
+    this.closedIntentionally = false // reset for next time
+
+    this.onclose?.()
+
+    if (this.enableReconnect && !wasIntentional) {
+      this.reconnect()
+    } else {
+      this.closeAllSubscriptions(reason)
+    }
+  }
+
   public async connect(): Promise<void> {
     if (this.connectionPromise) return this.connectionPromise
 
@@ -110,8 +152,23 @@ export class AbstractRelay {
       }
 
       this.ws.onopen = () => {
+        if (this.reconnectTimeoutHandle) {
+          clearTimeout(this.reconnectTimeoutHandle)
+          this.reconnectTimeoutHandle = undefined
+        }
         clearTimeout(this.connectionTimeoutHandle)
         this._connected = true
+        this.reconnectAttempts = 0
+
+        // resubscribe to all open subscriptions
+        for (const sub of this.openSubs.values()) {
+          sub.eosed = false
+          if (typeof this.enableReconnect === 'function') {
+            sub.filters = this.enableReconnect(sub.filters)
+          }
+          sub.fire()
+        }
+
         if (this.enablePing) {
           this.pingpong()
         }
@@ -121,19 +178,13 @@ export class AbstractRelay {
       this.ws.onerror = ev => {
         clearTimeout(this.connectionTimeoutHandle)
         reject((ev as any).message || 'websocket error')
-        this._connected = false
-        this.connectionPromise = undefined
-        this.onclose?.()
-        this.closeAllSubscriptions('relay connection errored')
+        this.handleHardClose('relay connection errored')
       }
 
       this.ws.onclose = ev => {
         clearTimeout(this.connectionTimeoutHandle)
         reject((ev as any).message || 'websocket closed')
-        this._connected = false
-        this.connectionPromise = undefined
-        this.onclose?.()
-        this.closeAllSubscriptions('relay connection closed')
+        this.handleHardClose('relay connection closed')
       }
 
       this.ws.onmessage = this._onmessage.bind(this)
@@ -145,7 +196,7 @@ export class AbstractRelay {
   private async waitForPingPong() {
     return new Promise((res, err) => {
       // listen for pong
-      ;(this.ws && this.ws.on && this.ws.on('pong', () => res(true))) || err("ws can't listen for pong")
+      this.ws && this.ws.on ? this.ws.on('pong', () => res(true)) : err("ws can't listen for pong")
       // send a ping
       this.ws && this.ws.ping && this.ws.ping()
     })
@@ -178,13 +229,12 @@ export class AbstractRelay {
       ])
       if (result) {
         // schedule another pingpong
-        setTimeout(() => this.pingpong(), this.pingFrequency)
+        this.pingTimeoutHandle = setTimeout(() => this.pingpong(), this.pingFrequency)
       } else {
         // pingpong closing socket
-        this.closeAllSubscriptions('pingpong timed out')
-        this._connected = false
-        this.onclose?.()
-        this.ws?.close()
+        if (this.ws?.readyState === WebSocket.OPEN) {
+          this.ws?.close()
+        }
       }
     }
   }
@@ -372,10 +422,21 @@ export class AbstractRelay {
   }
 
   public close() {
+    this.closedIntentionally = true
+    if (this.reconnectTimeoutHandle) {
+      clearTimeout(this.reconnectTimeoutHandle)
+      this.reconnectTimeoutHandle = undefined
+    }
+    if (this.pingTimeoutHandle) {
+      clearTimeout(this.pingTimeoutHandle)
+      this.pingTimeoutHandle = undefined
+    }
     this.closeAllSubscriptions('relay connection closed by us')
     this._connected = false
     this.onclose?.()
-    this.ws?.close()
+    if (this.ws?.readyState === WebSocket.OPEN) {
+      this.ws?.close()
+    }
   }
 
   // this is the function assigned to this.ws.onmessage

pool.test.ts

@@ -253,6 +253,120 @@ test('ping-pong timeout in pool', async () => {
   expect(closed).toBeTrue()
 })
 
+test('reconnect on disconnect in pool', async () => {
+  const mockRelay = mockRelays[0]
+  pool = new SimplePool({ enablePing: true, enableReconnect: true })
+  const relay = await pool.ensureRelay(mockRelay.url)
+  relay.pingTimeout = 50
+  relay.pingFrequency = 50
+  relay.resubscribeBackoff = [50, 100]
+
+  let closes = 0
+  relay.onclose = () => {
+    closes++
+  }
+
+  expect(relay.connected).toBeTrue()
+
+  // wait for the first ping to succeed
+  await new Promise(resolve => setTimeout(resolve, 75))
+  expect(closes).toBe(0)
+
+  // now make it unresponsive
+  mockRelay.unresponsive = true
+
+  // wait for the second ping to fail, which will trigger a close
+  await new Promise(resolve => {
+    const interval = setInterval(() => {
+      if (closes > 0) {
+        clearInterval(interval)
+        resolve(null)
+      }
+    }, 10)
+  })
+  expect(closes).toBe(1)
+  expect(relay.connected).toBeFalse()
+
+  // now make it responsive again
+  mockRelay.unresponsive = false
+
+  // wait for reconnect
+  await new Promise(resolve => {
+    const interval = setInterval(() => {
+      if (relay.connected) {
+        clearInterval(interval)
+        resolve(null)
+      }
+    }, 10)
+  })
+
+  expect(relay.connected).toBeTrue()
+  expect(closes).toBe(1)
+})
+
+test('reconnect with filter update in pool', async () => {
+  const mockRelay = mockRelays[0]
+  const newSince = Math.floor(Date.now() / 1000)
+  pool = new SimplePool({
+    enablePing: true,
+    enableReconnect: filters => {
+      return filters.map(f => ({ ...f, since: newSince }))
+    },
+  })
+  const relay = await pool.ensureRelay(mockRelay.url)
+  relay.pingTimeout = 50
+  relay.pingFrequency = 50
+  relay.resubscribeBackoff = [50, 100]
+
+  let closes = 0
+  relay.onclose = () => {
+    closes++
+  }
+
+  expect(relay.connected).toBeTrue()
+
+  const sub = relay.subscribe([{ kinds: [1], since: 0 }], { onevent: () => {} })
+  expect(sub.filters[0].since).toBe(0)
+
+  // wait for the first ping to succeed
+  await new Promise(resolve => setTimeout(resolve, 75))
+  expect(closes).toBe(0)
+
+  // now make it unresponsive
+  mockRelay.unresponsive = true
+
+  // wait for the second ping to fail, which will trigger a close
+  await new Promise(resolve => {
+    const interval = setInterval(() => {
+      if (closes > 0) {
+        clearInterval(interval)
+        resolve(null)
+      }
+    }, 10)
+  })
+  expect(closes).toBe(1)
+  expect(relay.connected).toBeFalse()
+
+  // now make it responsive again
+  mockRelay.unresponsive = false
+
+  // wait for reconnect
+  await new Promise(resolve => {
+    const interval = setInterval(() => {
+      if (relay.connected) {
+        clearInterval(interval)
+        resolve(null)
+      }
+    }, 10)
+  })
+
+  expect(relay.connected).toBeTrue()
+  expect(closes).toBe(1)
+
+  // check if filter was updated
+  expect(sub.filters[0].since).toBe(newSince)
+})
+
 test('track relays when publishing', async () => {
   let event1 = finalizeEvent(
     {

pool.ts

@@ -1,7 +1,7 @@
 /* global WebSocket */
 
 import { verifyEvent } from './pure.ts'
-import { AbstractSimplePool } from './abstract-pool.ts'
+import { AbstractSimplePool, type AbstractPoolConstructorOptions } from './abstract-pool.ts'
 
 var _WebSocket: typeof WebSocket
 
@@ -14,7 +14,7 @@ export function useWebSocketImplementation(websocketImplementation: any) {
 }
 
 export class SimplePool extends AbstractSimplePool {
-  constructor(options?: { enablePing?: boolean }) {
+  constructor(options?: Pick<AbstractPoolConstructorOptions, 'enablePing' | 'enableReconnect'>) {
     super({ verifyEvent, websocketImplementation: _WebSocket, ...options })
   }
 }