devp2p -> connection reliability: subdivided interval calls to refill RLPx peer connections to improve networking distribution and connection reliability

Author: holgerd77

packages/devp2p/src/dpt/dpt.ts

@@ -173,7 +173,9 @@ export class DPT extends EventEmitter {
     this._refreshIntervalSelectionCounter = (this._refreshIntervalSelectionCounter + 1) % 10
 
     const peers = this.getPeers()
-    debug(`call .refresh (${peers.length} peers in table)`)
+    debug(
+      `call .refresh() (selector ${this._refreshIntervalSelectionCounter}) (${peers.length} peers in table)`
+    )
 
     for (const peer of peers) {
       // Randomly distributed selector based on peer ID

packages/devp2p/src/rlpx/rlpx.ts

@@ -8,7 +8,7 @@ import LRUCache from 'lru-cache'
 import Common from '@ethereumjs/common'
 // note: relative path only valid in .js file in dist
 const { version: pVersion } = require('../../package.json')
-import { pk2id, createDeferred, formatLogId } from '../util'
+import { pk2id, createDeferred, formatLogId, buffer2int } from '../util'
 import { Peer, DISCONNECT_REASONS, Capabilities } from './peer'
 import { DPT, PeerInfo } from '../dpt'
 
@@ -31,6 +31,7 @@ export interface RLPxOptions {
 export class RLPx extends EventEmitter {
   _privateKey: Buffer
   _id: Buffer
+
   _timeout: number
   _maxPeers: number
   _clientId: Buffer
@@ -39,11 +40,14 @@ export class RLPx extends EventEmitter {
   _common: Common
   _listenPort: number | null
   _dpt: DPT | null
+
   _peersLRU: LRUCache<string, boolean>
   _peersQueue: { peer: PeerInfo; ts: number }[]
   _server: net.Server | null
   _peers: Map<string, net.Socket | Peer>
+
   _refillIntervalId: NodeJS.Timeout
+  _refillIntervalSelectionCounter: number = 0
 
   constructor(privateKey: Buffer, options: RLPxOptions) {
     super()
@@ -98,7 +102,9 @@ export class RLPx extends EventEmitter {
     this._peers = new Map()
     this._peersQueue = []
     this._peersLRU = new LRUCache({ max: 25000 })
-    this._refillIntervalId = setInterval(() => this._refillConnections(), ms('10s'))
+    const REFILL_INTERVALL = ms('10s')
+    const refillIntervalSubdivided = Math.floor(REFILL_INTERVALL / 10)
+    this._refillIntervalId = setInterval(() => this._refillConnections(), refillIntervalSubdivided)
   }
 
   listen(...args: any[]) {
@@ -261,17 +267,27 @@ export class RLPx extends EventEmitter {
   _refillConnections() {
     if (!this._isAlive()) return
     debug(
-      `refill connections.. peers: ${this._peers.size}, queue size: ${
-        this._peersQueue.length
-      }, open slots: ${this._getOpenSlots()}`
+      `refill connections.. (selector ${this._refillIntervalSelectionCounter}) peers: ${
+        this._peers.size
+      }, queue size: ${this._peersQueue.length}, open slots: ${this._getOpenSlots()}`
     )
+    // Rotating selection counter going in loop from 0..9
+    this._refillIntervalSelectionCounter = (this._refillIntervalSelectionCounter + 1) % 10
 
     this._peersQueue = this._peersQueue.filter((item) => {
       if (this._getOpenSlots() === 0) return true
       if (item.ts > Date.now()) return true
 
-      this._connectToPeer(item.peer)
-      return false
+      // Randomly distributed selector based on peer ID
+      // to decide on subdivided execution
+      const selector = buffer2int((item.peer.id! as Buffer).slice(0, 1)) % 10
+      if (selector === this._refillIntervalSelectionCounter) {
+        this._connectToPeer(item.peer)
+        return false
+      } else {
+        // Still keep peer in queue
+        return true
+      }
     })
   }
 }