fix: random walk (#104)

Author: jacobheun

package.json

@@ -37,6 +37,7 @@
   },
   "homepage": "https://github.com/libp2p/js-libp2p-kad-dht",
   "dependencies": {
+    "abort-controller": "^3.0.0",
     "async": "^2.6.2",
     "base32.js": "~0.1.0",
     "chai-checkmark": "^1.0.1",

src/constants.js

@@ -44,6 +44,6 @@ exports.defaultRandomWalk = {
   enabled: true,
   queriesPerPeriod: 1,
   interval: 5 * minute,
-  timeout: 10 * second,
+  timeout: 30 * second,
   delay: 10 * second
 }

src/index.js

@@ -38,7 +38,7 @@ class KadDHT extends EventEmitter {
    * @property {boolean} enabled discovery enabled (default: true)
    * @property {number} queriesPerPeriod how many queries to run per period (default: 1)
    * @property {number} interval how often to run the the random-walk process, in milliseconds (default: 300000)
-   * @property {number} timeout how long to wait for the the random-walk query to run, in milliseconds (default: 10000)
+   * @property {number} timeout how long to wait for the the random-walk query to run, in milliseconds (default: 30000)
    * @property {number} delay how long to wait before starting the first random walk, in milliseconds (default: 10000)
    */
 
@@ -173,11 +173,10 @@ class KadDHT extends EventEmitter {
    */
   stop (callback) {
     this._running = false
-    this.randomWalk.stop(() => { // guarantee that random walk is stopped if it was started
-      this.providers.stop()
-      this.network.stop(callback)
-    })
+    this.randomWalk.stop()
+    this.providers.stop()
     this._queryManager.stop()
+    this.network.stop(callback)
   }
 
   /**

src/random-walk.js

@@ -3,12 +3,12 @@
 const times = require('async/times')
 const crypto = require('libp2p-crypto')
 const waterfall = require('async/waterfall')
-const timeout = require('async/timeout')
 const multihashing = require('multihashing-async')
 const PeerId = require('peer-id')
 const assert = require('assert')
 const c = require('./constants')
 const { logger } = require('./utils')
+const AbortController = require('abort-controller')
 
 const errcode = require('err-code')
 
@@ -25,9 +25,8 @@ class RandomWalk {
    * @param {DHT} options.dht
    */
   constructor (dht, options) {
-    this._options = { ...c.defaultRandomWalk, ...options }
     assert(dht, 'Random Walk needs an instance of the Kademlia DHT')
-    this._runningHandle = null
+    this._options = { ...c.defaultRandomWalk, ...options }
     this._kadDHT = dht
     this.log = logger(dht.peerInfo.id, 'random-walk')
   }
@@ -41,64 +40,44 @@ class RandomWalk {
    */
   start () {
     // Don't run twice
-    if (this._running || !this._options.enabled) { return }
-
-    // Create running handle
-    const runningHandle = {
-      _onCancel: null,
-      _timeoutId: null,
-      runPeriodically: (walk, period) => {
-        runningHandle._timeoutId = setTimeout(() => {
-          runningHandle._timeoutId = null
-
-          walk((nextPeriod) => {
-            // Was walk cancelled while fn was being called?
-            if (runningHandle._onCancel) {
-              return runningHandle._onCancel()
-            }
-            // Schedule next
-            runningHandle.runPeriodically(walk, nextPeriod)
-          })
-        }, period)
-      },
-      cancel: (cb) => {
-        // Not currently running, can callback immediately
-        if (runningHandle._timeoutId) {
-          clearTimeout(runningHandle._timeoutId)
-          return cb()
-        }
-        // Wait to finish and then call callback
-        runningHandle._onCancel = cb
-      }
-    }
+    if (this._timeoutId || !this._options.enabled) { return }
 
     // Start doing random walks after `this._options.delay`
-    runningHandle._timeoutId = setTimeout(() => {
+    this._timeoutId = setTimeout(() => {
       // Start runner immediately
-      runningHandle.runPeriodically((done) => {
+      this._runPeriodically((done) => {
         // Each subsequent walk should run on a `this._options.interval` interval
         this._walk(this._options.queriesPerPeriod, this._options.timeout, () => done(this._options.interval))
       }, 0)
     }, this._options.delay)
-
-    this._runningHandle = runningHandle
   }
 
   /**
-   * Stop the random-walk process.
-   * @param {function(Error)} callback
+   * Stop the random-walk process. Any active
+   * queries will be aborted.
    *
    * @returns {void}
    */
-  stop (callback) {
-    const runningHandle = this._runningHandle
-
-    if (!runningHandle) {
-      return callback()
-    }
+  stop () {
+    clearTimeout(this._timeoutId)
+    this._timeoutId = null
+    this._controller && this._controller.abort()
+  }
 
-    this._runningHandle = null
-    runningHandle.cancel(callback)
+  /**
+   * Run function `walk` on every `interval` ms
+   * @param {function(callback)} walk The function to execute on `interval`
+   * @param {number} interval The interval to run on in ms
+   *
+   * @private
+   */
+  _runPeriodically (walk, interval) {
+    this._timeoutId = setTimeout(() => {
+      walk((nextInterval) => {
+        // Schedule next
+        this._runPeriodically(walk, nextInterval)
+      })
+    }, interval)
   }
 
   /**
@@ -113,39 +92,63 @@ class RandomWalk {
    */
   _walk (queries, walkTimeout, callback) {
     this.log('start')
+    this._controller = new AbortController()
 
-    times(queries, (i, cb) => {
+    times(queries, (i, next) => {
+      this.log('running query %d', i)
+
+      // Perform the walk
       waterfall([
         (cb) => this._randomPeerId(cb),
-        (id, cb) => timeout((cb) => {
-          this._query(id, cb)
-        }, walkTimeout)(cb)
+        (id, cb) => {
+          // Check if we've happened to already abort
+          if (!this._controller) return cb()
+
+          this._query(id, {
+            timeout: walkTimeout,
+            signal: this._controller.signal
+          }, cb)
+        }
       ], (err) => {
-        if (err) {
-          this.log.error('query finished with error', err)
-          return callback(err)
+        if (err && err.code !== 'ETIMEDOUT') {
+          this.log.error('query %d finished with error', i, err)
+          return next(err)
         }
 
-        this.log('done')
-        callback(null)
+        this.log('finished query %d', i)
+        next(null)
       })
+    }, (err) => {
+      this._controller = null
+      this.log('finished queries')
+      callback(err)
     })
   }
 
   /**
    * The query run during a random walk request.
    *
+   * TODO: While query currently supports an abort controller, it is not
+   * yet supported by `DHT.findPeer`. Once https://github.com/libp2p/js-libp2p-kad-dht/pull/82
+   * is complete, and AbortController support has been added to the
+   * DHT query functions, the abort here will just work, provided the
+   * functions support `options.signal`. Once done, this todo should be
+   * removed.
+   *
    * @param {PeerId} id
+   * @param {object} options
+   * @param {number} options.timeout
+   * @param {AbortControllerSignal} options.signal
    * @param {function(Error)} callback
    * @returns {void}
    *
    * @private
    */
-  _query (id, callback) {
+  _query (id, options, callback) {
     this.log('query:%s', id.toB58String())
 
-    this._kadDHT.findPeer(id, (err, peer) => {
-      if (err.code === 'ERR_NOT_FOUND') {
+    this._kadDHT.findPeer(id, options, (err, peer) => {
+      if (err && err.code === 'ERR_NOT_FOUND') {
         // expected case, we asked for random stuff after all
         return callback()
       }

test/kad-dht.spec.js

@@ -73,7 +73,7 @@ function connect (a, b, callback) {
 
 function bootstrap (dhts) {
   dhts.forEach((dht) => {
-    dht.randomWalk._walk(1, 1000, () => {})
+    dht.randomWalk._walk(1, 10000, () => {})
   })
 }
 
@@ -574,17 +574,13 @@ describe('KadDHT', () => {
   })
 
   it('random-walk', function (done) {
-    this.timeout(10 * 1000)
+    this.timeout(20 * 1000)
 
     const nDHTs = 20
     const tdht = new TestDHT()
 
     // random walk disabled for a manual usage
-    tdht.spawn(nDHTs, {
-      randomWalk: {
-        enabled: false
-      }
-    }, (err, dhts) => {
+    tdht.spawn(nDHTs, (err, dhts) => {
       expect(err).to.not.exist()
 
       series([