Fix | Refactored socket creation to simplify handling of socket creation

Refactors socket creation in SocketFinder.findSocket(...) to simplify handling of socket creation.

When the host resolves to a single address the driver now defers to getConnectedSocket(...)
to create the socket without spawning any threads. This happens regardless of whether we're
running on an IBM JDK. Previously the single address case would still use NIO on an IBM JDK.

On non-IBM JDKs the driver now handles both IPv4 and IPv6 addresses concurrently with a single
shared timeout. Previously hosts that resolved to both types of addresses were allowed half the
timeout for socket creation per address type with the resolution performed sequentially.

src/main/java/com/microsoft/sqlserver/jdbc/IOBuffer.java

@@ -2329,58 +2329,22 @@ else if (!useTnir) {
                 conn.terminate(SQLServerException.DRIVER_ERROR_UNSUPPORTED_CONFIG, errorStr);
             }
 
+            if (inetAddrs.length == 1) {
+                // Single address so do not start any threads
+                return getConnectedSocket(inetAddrs[0], portNumber, timeoutInMilliSeconds);
+            }
+            timeoutInMilliSeconds = Math.max(timeoutInMilliSeconds, minTimeoutForParallelConnections);                
             if (Util.isIBM()) {
-                timeoutInMilliSeconds = Math.max(timeoutInMilliSeconds, minTimeoutForParallelConnections);
                 if (logger.isLoggable(Level.FINER)) {
                     logger.finer(this.toString() + "Using Java NIO with timeout:" + timeoutInMilliSeconds);
                 }
                 findSocketUsingJavaNIO(inetAddrs, portNumber, timeoutInMilliSeconds);
             }
             else {
-                LinkedList<InetAddress> inet4Addrs = new LinkedList<>();
-                LinkedList<InetAddress> inet6Addrs = new LinkedList<>();
-
-                for (InetAddress inetAddr : inetAddrs) {
-                    if (inetAddr instanceof Inet4Address) {
-                        inet4Addrs.add((Inet4Address) inetAddr);
-                    }
-                    else {
-                        assert inetAddr instanceof Inet6Address : "Unexpected IP address " + inetAddr.toString();
-                        inet6Addrs.add((Inet6Address) inetAddr);
-                    }
-                }
-
-                // use half timeout only if both IPv4 and IPv6 addresses are present
-                int timeoutForEachIPAddressType;
-                if ((!inet4Addrs.isEmpty()) && (!inet6Addrs.isEmpty())) {
-                    timeoutForEachIPAddressType = Math.max(timeoutInMilliSeconds / 2, minTimeoutForParallelConnections);
-                }
-                else
-                    timeoutForEachIPAddressType = Math.max(timeoutInMilliSeconds, minTimeoutForParallelConnections);
-
-                if (!inet4Addrs.isEmpty()) {
-                    if (logger.isLoggable(Level.FINER)) {
-                        logger.finer(this.toString() + "Using Java Threading with timeout:" + timeoutForEachIPAddressType);
-                    }
-
-                    findSocketUsingThreading(inet4Addrs, portNumber, timeoutForEachIPAddressType);
-                }
-
-                if (!result.equals(Result.SUCCESS)) {
-                    // try threading logic
-                    if (!inet6Addrs.isEmpty()) {
-                        // do not start any threads if there is only one ipv6 address
-                        if (inet6Addrs.size() == 1) {
-                            return getConnectedSocket(inet6Addrs.get(0), portNumber, timeoutForEachIPAddressType);
-                        }
-
-                        if (logger.isLoggable(Level.FINER)) {
-                            logger.finer(this.toString() + "Using Threading with timeout:" + timeoutForEachIPAddressType);
-                        }
-
-                        findSocketUsingThreading(inet6Addrs, portNumber, timeoutForEachIPAddressType);
-                    }
+                if (logger.isLoggable(Level.FINER)) {
+                    logger.finer(this.toString() + "Using Threading with timeout:" + timeoutInMilliSeconds);
                 }
+                findSocketUsingThreading(inetAddrs, portNumber, timeoutInMilliSeconds);
             }
 
             // If the thread continued execution due to timeout, the result may not be known.
@@ -2633,20 +2597,20 @@ private Socket getConnectedSocket(InetSocketAddress addr,
         return selectedSocket;
     }
 
-    private void findSocketUsingThreading(LinkedList<InetAddress> inetAddrs,
+    private void findSocketUsingThreading(InetAddress[] inetAddrs,
             int portNumber,
             int timeoutInMilliSeconds) throws IOException, InterruptedException {
         assert timeoutInMilliSeconds != 0 : "The timeout cannot be zero";
 
-        assert inetAddrs.isEmpty() == false : "Number of inetAddresses should not be zero in this function";
+        assert inetAddrs.length != 0 : "Number of inetAddresses should not be zero in this function";
 
         LinkedList<Socket> sockets = new LinkedList<>();
         LinkedList<SocketConnector> socketConnectors = new LinkedList<>();
 
         try {
 
             // create a socket, inetSocketAddress and a corresponding socketConnector per inetAddress
-            noOfSpawnedThreads = inetAddrs.size();
+            noOfSpawnedThreads = inetAddrs.length;
             for (InetAddress inetAddress : inetAddrs) {
                 Socket s = new Socket();
                 sockets.add(s);