Fix a bug where a connection is not closed immediatley when HTTP/2 PI…

…NG write fails (#2699)

Motivation:

If a connection is closed unexpectedly due to a network problem,
the remote peer does not receive closing signals such as GOAWAY frame and
the connection is alive until cleaned up due to request timeout, idle timeout, or PING failure.

When PING write fails, KeepAliveHandler tries to close the connection, which takes as long as the idle timeout.
Because the idle timeout is configured as `gracefulShutdownTimeoutMillis` for Netty Http2ConnectionHandler.
https://github.com/line/armeria/blob/fec9fb833275eba59eb9afaf25fc8b7c28132f80/core/src/main/java/com/linecorp/armeria/server/Http2ServerConnectionHandler.java#L56-L62

Modifications:

* Close a connection immediately if KeepAliveHandler is closing.

Result:
A dead connection is cleaned up immediately when PING write fails.

core/src/main/java/com/linecorp/armeria/client/Http2ClientConnectionHandler.java

@@ -101,7 +101,9 @@ public void channelActive(ChannelHandlerContext ctx) throws Exception {
 
     @Override
     protected boolean needsImmediateDisconnection() {
-        return clientFactory.isClosing() || responseDecoder.goAwayHandler().receivedErrorGoAway();
+        return clientFactory.isClosing() ||
+               responseDecoder.goAwayHandler().receivedErrorGoAway() ||
+               keepAliveHandler.isClosing();
     }
 
     @Override

core/src/main/java/com/linecorp/armeria/internal/common/KeepAliveHandler.java

@@ -172,6 +172,10 @@ public final void onPing() {
         cancelFutures();
     }
 
+    public final boolean isClosing() {
+        return pingState == PingState.SHUTDOWN;
+    }
+
     protected abstract ChannelFuture writePing(ChannelHandlerContext ctx);
 
     protected abstract boolean pingResetsPreviousPing();

core/src/main/java/com/linecorp/armeria/server/Http2ServerConnectionHandler.java

@@ -67,7 +67,9 @@ final class Http2ServerConnectionHandler extends AbstractHttp2ConnectionHandler
 
     @Override
     protected boolean needsImmediateDisconnection() {
-        return gracefulShutdownSupport.isShuttingDown() || requestDecoder.goAwayHandler().receivedErrorGoAway();
+        return gracefulShutdownSupport.isShuttingDown() ||
+               requestDecoder.goAwayHandler().receivedErrorGoAway() ||
+               keepAliveHandler.isClosing();
     }
 
     @Override