The DB should now be able to connect to SRV records. It will also attempt to fail over once if a connection closes.

lib/util/srv.js

@@ -0,0 +1,79 @@
+var Promise = require('bluebird')
+var dns = Promise.promisifyAll(require('dns'))
+
+function groupByPriority(records) {
+  function sortByPriority(a, b) {
+    return a.priority - b.priority
+  }
+
+  return records.sort(sortByPriority).reduce(function(acc, record) {
+    if (acc.length) {
+      var last = acc[acc.length - 1]
+      if (last[0].priority !== record.priority) {
+        acc.push([record])
+      }
+      else {
+        last.push(record)
+      }
+    }
+    else {
+      acc.push([record])
+    }
+    return acc
+  }, [])
+}
+
+function shuffleWeighted(records) {
+  function sortByWeight(a, b) {
+    return b.weight - a.weight
+  }
+
+  function totalWeight(records) {
+    return records.reduce(function(sum, record) {
+      return sum + record.weight
+    }, 0)
+  }
+
+  function pick(records, sum) {
+    var rand = Math.random() * sum
+      , counter = 0
+
+    for (var i = 0, l = records.length; i < l; ++i) {
+      counter += records[i].weight
+      if (rand < counter) {
+        var picked = records.splice(i, 1)
+        return picked.concat(pick(records, sum - picked[0].weight))
+      }
+    }
+
+    return []
+  }
+
+  return pick(records.sort(sortByWeight), totalWeight(records))
+}
+
+function flatten(groupedRecords) {
+  return groupedRecords.reduce(function(acc, group) {
+    return acc.concat(group)
+  }, [])
+}
+
+var RE_SRV = /^srv:(.*)$/
+
+module.exports.sort = function(records) {
+  return flatten(groupByPriority(records).map(shuffleWeighted))
+}
+
+module.exports.resolve = function(domain, defaultPort) {
+  var match
+  if ((match = RE_SRV.exec(domain))) {
+    return dns.resolveSrvAsync(match[1])
+      .then(module.exports.sort)
+  }
+  else {
+    return Promise.resolve([{
+      name: domain
+    , port: defaultPort
+    }])
+  }
+}