Back port a few more #774 related changes.

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

@@ -16,17 +16,27 @@
 
 package com.zaxxer.hikari.pool;
 
+import static com.zaxxer.hikari.pool.PoolEntry.LASTACCESS_COMPARABLE;
+import static com.zaxxer.hikari.util.ConcurrentBag.IConcurrentBagEntry.STATE_IN_USE;
+import static com.zaxxer.hikari.util.ConcurrentBag.IConcurrentBagEntry.STATE_NOT_IN_USE;
+import static com.zaxxer.hikari.util.ConcurrentBag.IConcurrentBagEntry.STATE_REMOVED;
+import static com.zaxxer.hikari.util.UtilityElf.createThreadPoolExecutor;
+import static com.zaxxer.hikari.util.UtilityElf.quietlySleep;
+import static java.util.Collections.unmodifiableCollection;
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
 import static java.util.concurrent.TimeUnit.SECONDS;
 
 import java.sql.Connection;
 import java.sql.SQLException;
 import java.sql.SQLTransientConnectionException;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.Callable;
+import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Future;
+import java.util.concurrent.LinkedBlockingQueue;
 import java.util.concurrent.ScheduledThreadPoolExecutor;
 import java.util.concurrent.ThreadFactory;
 import java.util.concurrent.ThreadLocalRandom;
@@ -50,13 +60,6 @@ import com.zaxxer.hikari.util.ConcurrentBag.IBagStateListener;
 import com.zaxxer.hikari.util.SuspendResumeLock;
 import com.zaxxer.hikari.util.UtilityElf.DefaultThreadFactory;
 
-import static com.zaxxer.hikari.pool.PoolEntry.LASTACCESS_COMPARABLE;
-import static com.zaxxer.hikari.util.ConcurrentBag.IConcurrentBagEntry.STATE_IN_USE;
-import static com.zaxxer.hikari.util.ConcurrentBag.IConcurrentBagEntry.STATE_NOT_IN_USE;
-import static com.zaxxer.hikari.util.ConcurrentBag.IConcurrentBagEntry.STATE_REMOVED;
-import static com.zaxxer.hikari.util.UtilityElf.createThreadPoolExecutor;
-import static com.zaxxer.hikari.util.UtilityElf.quietlySleep;
-
 /**
  * This is the primary connection pool class that provides the basic
  * pooling behavior for HikariCP.
@@ -80,6 +83,7 @@ public class HikariPool extends PoolBase implements HikariPoolMXBean, IBagStateL
 
    private final PoolEntryCreator POOL_ENTRY_CREATOR = new PoolEntryCreator();
    private final AtomicInteger totalConnections;
+   private final Collection<Runnable> addConnectionQueue;
    private final ThreadPoolExecutor addConnectionExecutor;
    private final ThreadPoolExecutor closeConnectionExecutor;
    private final ScheduledThreadPoolExecutor houseKeepingExecutorService;
@@ -118,6 +122,9 @@ public class HikariPool extends PoolBase implements HikariPoolMXBean, IBagStateL
       registerMBeans(this);
 
       ThreadFactory threadFactory = config.getThreadFactory();
+
+      LinkedBlockingQueue<Runnable> addConnectionQueue = new LinkedBlockingQueue<>(config.getMaximumPoolSize() + 1);
+      this.addConnectionQueue = unmodifiableCollection(addConnectionQueue);
       this.addConnectionExecutor = createThreadPoolExecutor(config.getMaximumPoolSize(), poolName + " connection adder", threadFactory, new ThreadPoolExecutor.DiscardPolicy());
       this.closeConnectionExecutor = createThreadPoolExecutor(config.getMaximumPoolSize(), poolName + " connection closer", threadFactory, new ThreadPoolExecutor.CallerRunsPolicy());
 
@@ -297,7 +304,12 @@ public class HikariPool extends PoolBase implements HikariPoolMXBean, IBagStateL
    @Override
    public Future<Boolean> addBagItem()
    {
-      return addConnectionExecutor.submit(POOL_ENTRY_CREATOR);
+      final int connectionsToAdd = connectionBag.getPendingQueue() - addConnectionQueue.size();
+      if (connectionsToAdd > 0) {
+         return addConnectionExecutor.submit(POOL_ENTRY_CREATOR);
+      }
+
+      return CompletableFuture.completedFuture(Boolean.TRUE);
    }
 
    // ***********************************************************************
@@ -461,9 +473,9 @@ public class HikariPool extends PoolBase implements HikariPoolMXBean, IBagStateL
    private void fillPool()
    {
       final int connectionsToAdd = Math.min(config.getMaximumPoolSize() - totalConnections.get(), config.getMinimumIdle() - getIdleConnections())
-                                   - addConnectionExecutor.getQueue().size();
+                                   - addConnectionQueue.size();
       for (int i = 0; i < connectionsToAdd; i++) {
-         addBagItem();
+         addConnectionExecutor.submit(POOL_ENTRY_CREATOR);
       }
 
       if (connectionsToAdd > 0 && LOGGER.isDebugEnabled()) {