Resolve high thread count when using findSocketUsingThreading (#2104)

* Close a resource leak to prevent thread spawn.

* Add resource leak fix.

* Added test for thread count during find socket using threading.

* Changed threshold to 5x

* Changing servername from 'localhost' to prevent test failures.

* Replace explicit close for socket, with try

* Delete test.java that shouldn't have been pushed

* Playing with the threadPoolExecutor thread limit.

* ..

* Increase threshold.

* Removed TODO

* After catching exception, we should continue.

* Removed lingering artifacts.

* Added debugging

* More debugging

* Even more debugging.

* More debugging...

* Try sleep change.

* Trying without fix again to see coco behaviour with a final weight of 20000.

* 10,000

* Addded some debugging in the IOBUffer

* ...

* Added condition to force multithreading.

* More debugging earlier on

* Edit test

* More debugging.

* Added print statements further up in the call stack.

* for some reason, we're not logging

* More debug

* Trying without setting localhost in the test as this messes things up.

* Manually set the iNetAddress to confirm the test is actually running.

* Cleanup

* Final cleanup before review.

* Test cleanup.

* We can't ignore the InterruptedException. If we catch, log, and interrupt the thread.

* We don't want to continue, we don't to reinterrupt.

* A different try with reflection.

* One more try with reflection.

* Exclude junit test from DB and DW.

* whitespace

* Remove localhost?

* Moved back in localhost, otherwise the correct condition is not reached, and the multithread route is not used.

* Check for localhost + PR comments

* ...

* Resolve failures that came up after inserting assertTrue() statement

* Cleanup again

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

@@ -2954,7 +2954,16 @@ private void findSocketUsingThreading(InetAddress[] inetAddrs, int portNumber,
                     if (timeRemaining <= 0 || (!result.equals(Result.UNKNOWN)))
                         break;
 
-                    parentCondition.await(timeRemaining, TimeUnit.MILLISECONDS);
+                    try {
+                        parentCondition.await(timeRemaining, TimeUnit.MILLISECONDS);
+                    } catch (InterruptedException ie) {
+                        // Don't re-interrupt the current thread here.
+                        //
+                        // Thread interrupt is how parentCondition.signalAll works, signaling any thread on await.
+                        // Re-interrupting will just interrupt the next Sleep call that follows this logic path in the
+                        // loop in the SqlServerConnection.login method, causing too many, too fast retries.
+                        // Instead consume the interruption, and let the thread continue.
+                    }
 
                     if (logger.isLoggable(Level.FINER)) {
                         logger.finer(this.toString() + " The parent thread wokeup.");

src/test/java/com/microsoft/sqlserver/jdbc/SQLServerConnectionTest.java

@@ -11,6 +11,7 @@
 
 import java.io.IOException;
 import java.io.Reader;
+import java.lang.management.ManagementFactory;
 import java.sql.Clob;
 import java.sql.Connection;
 import java.sql.DriverManager;
@@ -32,6 +33,7 @@
 import javax.sql.ConnectionEvent;
 import javax.sql.PooledConnection;
 
+import org.junit.Assume;
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Tag;
 import org.junit.jupiter.api.Test;
@@ -934,6 +936,65 @@ public void run() {
         assertTrue(status && future.isCancelled(), TestResource.getResource("R_threadInterruptNotSet"));
     }
 
+
+   /**
+    * Test thread count when finding socket using threading.
+    */
+   @Test
+   @Tag(Constants.xAzureSQLDB)
+   @Tag(Constants.xAzureSQLDW)
+   public void testThreadCountWhenFindingSocket() {
+       ExecutorService executor = null;
+       ManagementFactory.getThreadMXBean().resetPeakThreadCount();
+
+       // First, check to see if there is a reachable local host, or else test will fail.
+       try {
+           SQLServerDataSource ds = new SQLServerDataSource();
+           ds.setServerName("localhost");
+           Connection con = ds.getConnection();
+       } catch (SQLServerException e) {
+           // Assume this will be an error different than 'localhost is unreachable'. If it is 'localhost is
+           // unreachable' abort and skip the test.
+           Assume.assumeFalse(e.getMessage().startsWith(TestResource.getResource("R_tcpipConnectionToHost")));
+       }
+
+       try {
+           executor = Executors.newSingleThreadExecutor(r -> new Thread(r, ""));
+           executor.submit(() -> {
+               try {
+                   SQLServerDataSource ds = new SQLServerDataSource();
+                   ds.setServerName("localhost");
+                   Thread.sleep(5000);
+                   Connection conn2 = ds.getConnection();
+               } catch (Exception e) {
+                   if (!(e instanceof SQLServerException)) {
+                       fail(TestResource.getResource("R_unexpectedException") + e.getMessage());
+                   }
+               }
+           });
+           SQLServerDataSource ds = new SQLServerDataSource();
+           ds.setServerName("localhost");
+           Connection conn = ds.getConnection();
+           Thread.sleep(5000);
+       } catch (Exception e) {
+           if (!(e instanceof SQLServerException)) {
+               fail(TestResource.getResource("R_unexpectedException") + e.getMessage());
+           }
+       } finally {
+           if (executor != null) {
+               executor.shutdown();
+           }
+       }
+
+       // At this point, thread count has returned to normal. If the peak was more
+       // than 2 times the current, this is an issue and the test should fail.
+       if (ManagementFactory.getThreadMXBean().getPeakThreadCount()
+               > 2 * ManagementFactory.getThreadMXBean().getThreadCount()) {
+           fail(TestResource.getResource("R_unexpectedThreadCount"));
+       }
+   }
+
+
     /**
      * Test calling method to get redirected server string.
      */

src/test/java/com/microsoft/sqlserver/jdbc/TestResource.java

@@ -202,5 +202,6 @@ protected Object[][] getContents() {
             {"R_cekDecryptionFailed", "Failed to decrypt a column encryption key using key store provider: {0}."},
             {"R_connectTimedOut", "connect timed out"},
             {"R_sessionKilled", "Cannot continue the execution because the session is in the kill state"},
-            {"R_failedFedauth", "Failed to acquire fedauth token: "}};
+            {"R_failedFedauth", "Failed to acquire fedauth token: "},
+            {"R_unexpectedThreadCount", "Thread count is higher than expected."}};
 }