[GitHub] [incubator-pekko] pjfanning commented on a diff in pull request #288: =act Refactory AsyncDnsResolver to fix the race condition of `nextId()`

["pjfanning (via GitHub)" <gi...@apache.org>]

pjfanning commented on code in PR #288:
URL: https://github.com/apache/incubator-pekko/pull/288#discussion_r1167202012


##########
actor/src/main/scala/org/apache/pekko/io/dns/internal/AsyncDnsResolver.scala:
##########
@@ -47,110 +46,149 @@ private[io] final class AsyncDnsResolver(
 
   import AsyncDnsResolver._
 
-  implicit val ec: ExecutionContextExecutor = context.dispatcher
+  initCache(cache)
 
-  // avoid ever looking up localhost by pre-populating cache
-  {
-    val loopback = InetAddress.getLoopbackAddress
-    val (ipv4Address, ipv6Address) = loopback match {
-      case ipv6: Inet6Address => (InetAddress.getByName("127.0.0.1"), ipv6)
-      case ipv4: Inet4Address => (ipv4, InetAddress.getByName("::1"))
-      case unknown            => throw new IllegalArgumentException(s"Loopback address was [$unknown]")
-    }
-    cache.put(
-      "localhost" -> Ip(),
-      DnsProtocol.Resolved("localhost", ARecord("localhost", Ttl.effectivelyForever, loopback) :: Nil),
-      Ttl.effectivelyForever)
-    cache.put(
-      "localhost" -> Ip(ipv6 = false, ipv4 = true),
-      DnsProtocol.Resolved("localhost", ARecord("localhost", Ttl.effectivelyForever, ipv4Address) :: Nil),
-      Ttl.effectivelyForever)
-    cache.put(
-      "localhost" -> Ip(ipv6 = true, ipv4 = false),
-      DnsProtocol.Resolved("localhost", ARecord("localhost", Ttl.effectivelyForever, ipv6Address) :: Nil),
-      Ttl.effectivelyForever)
-
-  }
-
-  // For ask to DNS Client
-  implicit val timeout: Timeout = Timeout(settings.ResolveTimeout)
-
-  val nameServers = settings.NameServers
-
-  val positiveCachePolicy = settings.PositiveCachePolicy
-  val negativeCachePolicy = settings.NegativeCachePolicy
   log.debug(
     "Using name servers [{}] and search domains [{}] with ndots={}",
-    nameServers,
+    settings.NameServers,
     settings.SearchDomains,
     settings.NDots)
 
-  private var requestId: Short = 0
-
-  private def nextId(): Short = {
-    requestId = (requestId + 1).toShort
-    requestId
-  }

Review Comment:
   is there a test case that shows this?
   
   I'm broadly supportive of fixing this - but I am wondering if a singleton actor instance would be a more actor based solution. Actor instances show only be processing 1 message at a time.



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