make socket saturation take request-per-seconds into account to avoid starvation when lots of timeouts happen

index.js

@@ -25,6 +25,7 @@ class DHT extends EventEmitter {
     this.bootstrapped = false
     this.destroyed = false
     this.concurrency = 16
+    this.concurrencyRPS = 50
     this.socket = opts.socket || dgram.createSocket('udp4')
     this.id = randomBytes(32)
     this.inflightQueries = 0

lib/io.js

@@ -2,6 +2,7 @@ const { Message, Holepunch, TYPE } = require('./messages')
 const blake2b = require('./blake2b')
 const peers = require('ipv4-peers')
 const sodium = require('sodium-universal')
+const speedometer = require('speedometer')
 
 const QUERY = Symbol('QUERY')
 const UPDATE = Symbol('UPDATE')
@@ -28,6 +29,7 @@ class IO {
     this._ticking = false
     this._tickInterval = setInterval(this._ontick.bind(this), 750)
     this._rotateInterval = setInterval(this._onrotate.bind(this), 300000)
+    this._speed = speedometer()
 
     socket.on('message', this._onmessage.bind(this))
   }
@@ -120,6 +122,10 @@ class IO {
     }
   }
 
+  _saturated () {
+    return this._speed(0) >= this._ctx.concurrencyRPS && this.inflight.length >= this._ctx.concurrency
+  }
+
   _finish (rid, err, val, peer) {
     const req = this._requests[rid]
     if (!req) return
@@ -135,7 +141,7 @@ class IO {
 
     req.callback(err, val, peer, req.message, req.peer, type)
 
-    while (this._pending.length && this.inflight.length < this._ctx.concurrency) {
+    while (this._pending.length && !this._saturated()) {
       const { message, peer, callback } = this._pending.shift()
       this._requestImmediately(message, peer, callback)
     }
@@ -143,7 +149,7 @@ class IO {
 
   _request (message, peer, callback) {
     // Should we wait to send?
-    if (this._pending.length || (this.inflight.length >= this._ctx.concurrency)) {
+    if (this._pending.length || this._saturated()) {
       this._pending.push({ message, peer, callback })
     } else {
       this._requestImmediately(message, peer, callback)
@@ -154,6 +160,8 @@ class IO {
     const rid = message.rid = this._free()
     const buffer = Message.encode(message)
 
+    this._speed(1)
+
     const req = {
       rid,
       index: this.inflight.length,
@@ -189,7 +197,8 @@ class IO {
       const req = this.inflight[i]
 
       if (req.timeout === 2 && ++req.tries < TRIES) {
-        this._retry(req)
+        if (this._saturated()) req.tries--
+        else this._retry(req)
         continue
       }
 

package.json

@@ -28,6 +28,7 @@
     "k-bucket": "^5.0.0",
     "protocol-buffers-encodings": "^1.1.0",
     "sodium-universal": "^2.0.0",
+    "speedometer": "^1.1.0",
     "stream-collector": "^1.0.1",
     "time-ordered-set": "^1.0.1",
     "xor-distance": "^2.0.0"