Explicitly wait for the initial SETTINGS frame for some tests.

src/main/java/com/relayrides/pushy/apns/ApnsClient.java

@@ -791,6 +791,13 @@ public boolean isConnected() {
         return (connectionReadyPromise != null && connectionReadyPromise.isSuccess());
     }
 
+    /*
+     * Waits for the initial SETTINGS frame from the server after connecting. For testing purposes only.
+     */
+    void waitForInitialSettings() throws InterruptedException {
+        this.connectionReadyPromise.channel().pipeline().get(ApnsClientHandler.class).waitForInitialSettings();
+    }
+
     /**
      * <p>Returns a {@code Future} that will succeed when the client has re-established a connection to the APNs gateway.
      * Callers may use this method to determine when it is safe to resume sending notifications after a send attempt

src/main/java/com/relayrides/pushy/apns/ApnsClientHandler.java

@@ -26,6 +26,7 @@
 import java.util.Map;
 import java.util.Random;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -58,6 +59,7 @@
 
 class ApnsClientHandler<T extends ApnsPushNotification> extends Http2ConnectionHandler {
 
+    private final AtomicBoolean receivedInitialSettings = new AtomicBoolean(false);
     private long nextStreamId = 1;
 
     private final Map<Integer, T> pushNotificationsByStreamId = new HashMap<>();
@@ -137,6 +139,16 @@ public ApnsClientHandler<S> build() {
     }
 
     private class ApnsClientHandlerFrameAdapter extends Http2FrameAdapter {
+        @Override
+        public void onSettingsRead(final ChannelHandlerContext context, final Http2Settings settings) {
+            log.trace("Received settings from APNs gateway: {}", settings);
+
+            synchronized (ApnsClientHandler.this.receivedInitialSettings) {
+                ApnsClientHandler.this.receivedInitialSettings.set(true);
+                ApnsClientHandler.this.receivedInitialSettings.notifyAll();
+            }
+        }
+
         @Override
         public int onDataRead(final ChannelHandlerContext context, final int streamId, final ByteBuf data, final int padding, final boolean endOfStream) throws Http2Exception {
             log.trace("Received data from APNs gateway on stream {}: {}", streamId, data.toString(UTF8));
@@ -338,4 +350,15 @@ public void exceptionCaught(final ChannelHandlerContext context, final Throwable
             log.warn("APNs client pipeline caught an exception.", cause);
         }
     }
+
+    /*
+     * Waits for the initial SETTINGS frame from the server after connecting. For testing purposes only.
+     */
+    void waitForInitialSettings() throws InterruptedException {
+        synchronized (this.receivedInitialSettings) {
+            while (!this.receivedInitialSettings.get()) {
+                this.receivedInitialSettings.wait();
+            }
+        }
+    }
 }

src/test/java/com/relayrides/pushy/apns/ApnsClientTest.java

@@ -19,8 +19,8 @@
 import java.util.List;
 import java.util.Random;
 import java.util.UUID;
-import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.atomic.AtomicInteger;
 
 import org.junit.After;
 import org.junit.AfterClass;
@@ -434,6 +434,25 @@ public void testSendNotification() throws Exception {
         assertTrue(response.isAccepted());
     }
 
+    /*
+     * This addresses an issue identified in https://github.com/relayrides/pushy/issues/283 where the initial SETTINGS
+     * frame from the server would trigger a flush, which was masking some issues with the deferred flush code.
+     */
+    @Test
+    public void testSendNotificationAfterInitialSettings() throws Exception {
+        this.client.waitForInitialSettings();
+
+        final String testToken = ApnsClientTest.generateRandomToken();
+
+        this.server.registerToken(DEFAULT_TOPIC, testToken);
+
+        final SimpleApnsPushNotification pushNotification = new SimpleApnsPushNotification(testToken, null, "test-payload");
+        final PushNotificationResponse<SimpleApnsPushNotification> response =
+                this.client.sendNotification(pushNotification).get();
+
+        assertTrue(response.isAccepted());
+    }
+
     @Test
     public void testSendNotificationWithImmediateFlush() throws Exception {
         this.client.disconnect().await();