Skip nodeset update on relayed isMaster response (ReactiveMongo#1235)

Author: cchantep

driver/src/main/scala/core/actors/MongoDBSystem.scala

@@ -1317,8 +1317,8 @@ private[reactivemongo] trait MongoDBSystem extends Actor { selfSystem =>
 
     val updated = {
       val respTo = response.header.responseTo
-      @inline def event =
-        s"IsMaster(${isMaster.isMaster}, ${respTo}, ${_nodeSet.toShortString})"
+
+      @inline def event = s"IsMasterResponse(${isMaster.isMaster}, ${respTo}, ${_nodeSet.toShortString})"
 
       updateNodeSet(event) { nodeSet =>
         val nodeSetWasReachable = nodeSet.isReachable
@@ -1327,8 +1327,14 @@ private[reactivemongo] trait MongoDBSystem extends Actor { selfSystem =>
         val nanow = System.nanoTime()
 
         // Update the details of the node corresponding to the response chan
-        val prepared =
-          nodeSet.updateNodeByChannelId(response.info.channelId) { node =>
+        import nodeSet.{updateNodeByChannelId=>updateNode}
+
+        val prepared = updateNode(response.info.channelId) { node =>
+          if (respTo < node.pingInfo.lastIsMasterId) {
+            warn(s"Skip node update for delated response #$respTo < last #${node.pingInfo.lastIsMasterId}")
+
+            node
+          } else {
             val pingTime: Long = {
               if (node.pingInfo.lastIsMasterId == respTo) {
                 nanow - node.pingInfo.lastIsMasterTime
@@ -1389,6 +1395,7 @@ private[reactivemongo] trait MongoDBSystem extends Actor { selfSystem =>
 
             n
           }
+        }
 
         val discoveredNodes = isMaster.replicaSet.toSeq.flatMap {
           _.hosts.collect {

driver/src/main/scala/core/nodeset/Node.scala

@@ -195,17 +195,15 @@ private[reactivemongo] final class Node(
   }
 
   lazy val toShortString = {
-    def latency = {
-      import pingInfo.{ ping => ns }
-
+    def hns(ns: Long): String = {
       if (ns < 1000L) s"${ns.toString}ns"
       else if (ns < 100000000L) s"${(ns / 1000000L).toString}ms"
       else s"${(ns / 1000000000L).toString}s"
     }
 
-    s"""Node[$name: $status<${statusChanged}ns> (${authenticatedConnections.size}/${connected.size}/${connections
+    s"""Node[$name: $status<${hns(statusChanged)}> (${authenticatedConnections.size}/${connected.size}/${connections
         .filterNot(_.signaling)
-        .size} available connections), latency=${latency}, authenticated={${authenticated
+        .size} available connections), latency=${hns(pingInfo.ping)}, authenticated={${authenticated
         .map(_.toShortString) mkString ", "}}]"""
   }