Fail fast for closed pool health checks

src/main/java/com/zaxxer/hikari/metrics/dropwizard/CodahaleHealthChecker.java

@@ -93,6 +93,10 @@ private static class ConnectivityHealthCheck extends HealthCheck
       @Override
       protected Result check() throws Exception
       {
+         if (pool.poolState == HikariPool.POOL_SHUTDOWN) {
+            return Result.unhealthy("Pool is shutdown");
+         }
+
          try (Connection connection = pool.getConnection(checkTimeoutMs)) {
             return Result.healthy();
          }

src/test/java/com/zaxxer/hikari/pool/CodahaleMetricsTest.java

@@ -39,6 +39,7 @@
 import static com.zaxxer.hikari.pool.TestElf.newHikariDataSource;
 import static com.zaxxer.hikari.util.UtilityElf.quietlySleep;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 import static org.junit.Assume.assumeFalse;
@@ -97,6 +98,29 @@ public void testHealthChecks() throws Exception
       }
    }
 
+   @Test
+   public void testConnectivityHealthCheckFailsFastAfterShutdown()
+   {
+      HealthCheckRegistry healthRegistry = new HealthCheckRegistry();
+
+      HikariConfig config = newHikariConfig();
+      config.setMaximumPoolSize(1);
+      config.setMinimumIdle(0);
+      config.setHealthCheckRegistry(healthRegistry);
+      config.setDataSourceClassName("com.zaxxer.hikari.mocks.StubDataSource");
+      config.addHealthCheckProperty("connectivityCheckTimeoutMs", "750");
+
+      HikariDataSource ds = new HikariDataSource(config);
+      ds.close();
+
+      final var start = System.nanoTime();
+      final var result = healthRegistry.runHealthCheck("testConnectivityHealthCheckFailsFastAfterShutdown.pool.ConnectivityCheck");
+      final var elapsedMs = TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - start);
+
+      assertFalse(result.isHealthy());
+      assertTrue("Health check waited " + elapsedMs + "ms after shutdown", elapsedMs < 250);
+   }
+
    @Test
    public void testSetters1() throws Exception
    {