replace ServerRegistration#unfurlSrv to DNSResolver class

lib/dns.js

@@ -0,0 +1,69 @@
+const dns = require('dns')
+
+const logger = require('./logger')
+const TimeTracker = require('./time')
+
+const config = require('../config')
+
+const SKIP_SRV_TIMEOUT = config.skipSrvTimeout || 60 * 60 * 1000
+
+class DNSResolver {
+  constructor (ip, port) {
+    this._ip = ip
+    this._port = port
+  }
+
+  _skipSrv () {
+    this._skipSrvUntil = TimeTracker.getEpochMillis() + SKIP_SRV_TIMEOUT
+  }
+
+  _isSkipSrv () {
+    return this._skipSrvUntil && TimeTracker.getEpochMillis() <= this._skipSrvUntil
+  }
+
+  resolve (callback) {
+    if (this._isSkipSrv()) {
+      callback(this._ip, this._port, config.rates.connectTimeout)
+
+      return
+    }
+
+    const startTime = TimeTracker.getEpochMillis()
+
+    let callbackFired = false
+
+    const fireCallback = (ip, port) => {
+      if (!callbackFired) {
+        callbackFired = true
+
+        // Send currentTime - startTime to provide remaining connectionTime allowance
+        callback(ip || this._ip, port || this._port, TimeTracker.getEpochMillis() - startTime)
+      }
+    }
+
+    const timeoutCallback = setTimeout(fireCallback, config.rates.connectTimeout)
+
+    dns.resolveSrv('_minecraft._tcp.' + this._ip, (err, records) => {
+      // Cancel the timeout handler if not already fired
+      if (!callbackFired) {
+        clearTimeout(timeoutCallback)
+      }
+
+      // Test if the error indicates a miss, or if the records returned are empty
+      if ((err && (err.code === 'ENOTFOUND' || err.code === 'ENODATA')) || !records || records.length === 0) {
+        if (!this._isSkipSrv()) {
+          this._skipSrv()
+
+          logger.log('warn', 'No SRV records were resolved for %s. Minetrack will skip attempting to resolve %s SRV records for %d minutes.', this._ip, this._ip, SKIP_SRV_TIMEOUT / (60 * 1000))
+        }
+
+        fireCallback()
+      } else {
+        // Only fires if !err && records.length > 0
+        fireCallback(records[0].name, records[0].port)
+      }
+    })
+  }
+}
+
+module.exports = DNSResolver