reverted. using cachedExecutor for setting network timeout as before

src/main/java/com/zaxxer/hikari/pool/HikariPool.java

@@ -236,6 +236,7 @@ public class HikariPool extends PoolBase implements HikariPoolMXBean, IBagStateL
             assassinExecutor.awaitTermination(5L, TimeUnit.SECONDS);
          }
 
+         shutdownNetworkTimeoutExecutor();
          closeConnectionExecutor.shutdown();
          closeConnectionExecutor.awaitTermination(5L, TimeUnit.SECONDS);
       }

src/main/java/com/zaxxer/hikari/pool/PoolBase.java

@@ -13,6 +13,9 @@ import java.sql.SQLException;
 import java.sql.Statement;
 import java.util.Properties;
 import java.util.concurrent.Executor;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ThreadFactory;
+import java.util.concurrent.ThreadPoolExecutor;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicReference;
 
@@ -29,6 +32,7 @@ import com.zaxxer.hikari.util.ClockSource;
 import com.zaxxer.hikari.util.DriverDataSource;
 import com.zaxxer.hikari.util.PropertyElf;
 import com.zaxxer.hikari.util.UtilityElf;
+import com.zaxxer.hikari.util.UtilityElf.DefaultThreadFactory;
 
 abstract class PoolBase
 {
@@ -47,6 +51,7 @@ abstract class PoolBase
    private int transactionIsolation;
    private int isNetworkTimeoutSupported;
    private int isQueryTimeoutSupported;
+   private Executor netTimeoutExecutor;
    private DataSource dataSource;
 
    private final String catalog;
@@ -55,7 +60,6 @@ abstract class PoolBase
    private final boolean isUseJdbc4Validation;
    private final boolean isIsolateInternalQueries;
    private final AtomicReference<Throwable> lastConnectionFailure;
-   private final Executor netTimeoutExecutor;
 
    private volatile boolean isValidChecked;
 
@@ -78,7 +82,6 @@ abstract class PoolBase
       this.connectionTimeout = config.getConnectionTimeout();
       this.validationTimeout = config.getValidationTimeout();
       this.lastConnectionFailure = new AtomicReference<>();
-      this.netTimeoutExecutor = new SynchronousExecutor();
 
       initializeDataSource();
    }
@@ -199,6 +202,13 @@ abstract class PoolBase
       }
    }
 
+   void shutdownNetworkTimeoutExecutor()
+   {
+      if (netTimeoutExecutor instanceof ThreadPoolExecutor) {
+         ((ThreadPoolExecutor) netTimeoutExecutor).shutdownNow();
+      }
+   }
+
    // ***********************************************************************
    //                       JMX methods
    // ***********************************************************************
@@ -285,6 +295,7 @@ abstract class PoolBase
 
       if (dataSource != null) {
          setLoginTimeout(dataSource, connectionTimeout);
+         createNetworkTimeoutExecutor(dataSource, dsClassName, jdbcUrl);
       }
 
       this.dataSource = dataSource;
@@ -464,6 +475,24 @@ abstract class PoolBase
       }
    }
 
+   private void createNetworkTimeoutExecutor(final DataSource dataSource, final String dsClassName, final String jdbcUrl)
+   {
+      // Temporary hack for MySQL issue: http://bugs.mysql.com/bug.php?id=75615
+      if ((dsClassName != null && dsClassName.contains("Mysql")) ||
+          (jdbcUrl != null && jdbcUrl.contains("mysql")) ||
+          (dataSource != null && dataSource.getClass().getName().contains("Mysql"))) {
+         netTimeoutExecutor = new SynchronousExecutor();
+      }
+      else {
+         ThreadFactory threadFactory = config.getThreadFactory();
+         threadFactory = threadFactory != null ? threadFactory : new DefaultThreadFactory("Hikari JDBC-timeout executor", true);
+         ThreadPoolExecutor executor = (ThreadPoolExecutor) Executors.newCachedThreadPool(threadFactory);
+         executor.allowCoreThreadTimeOut(true);
+         executor.setKeepAliveTime(15, TimeUnit.SECONDS);
+         netTimeoutExecutor = executor;
+      }
+   }
+
    private static class SynchronousExecutor implements Executor
    {
       /** {@inheritDoc} */