Add drainTimeout property to Http2Protocol/Http2UpgradeHandler

java/org/apache/coyote/http2/Http2Protocol.java

@@ -112,6 +112,19 @@ public class Http2Protocol implements UpgradeProtocol {
     private boolean discardRequestsAndResponses = false;
     private final SynchronizedStack<Request> recycledRequestsAndResponses = new SynchronizedStack<>();
 
+    /*
+     * Additional time in nanoseconds between sending the first graceful GOAWAY (max stream id) and the final GOAWAY
+     * (last seen stream id). During this time the server will continue to process new streams on the connection.
+     * This is to mitigate the race of client-buffered/sent packets for new streams and the final GOAWAY (with last
+     * seen stream id). By default, Tomcat uses the last computed RTT for this interval, but the RTT might have
+     * fluctuated due to network or server load conditions, or the client (e.g. nghttp2) might have already buffered
+     * frames for opening new streams on a connection.
+     *
+     * The name "drainTimeout" is taken from Envoy proxy's identical HTTP Connection Manager property and means exactly
+     * the same.
+     */
+    private long drainTimeout;
+
     @Override
     public String getHttpUpgradeName(boolean isSSLEnabled) {
         if (isSSLEnabled) {
@@ -409,6 +422,16 @@ public void setDiscardRequestsAndResponses(boolean discardRequestsAndResponses)
     }
 
 
+    public long getDrainTimeout() {
+        return drainTimeout;
+    }
+
+
+    public void setDrainTimeout(long drainTimeout) {
+        this.drainTimeout = drainTimeout;
+    }
+
+
     Request popRequestAndResponse() {
         Request requestAndResponse = null;
         if (!discardRequestsAndResponses) {

java/org/apache/coyote/http2/Http2UpgradeHandler.java

@@ -140,6 +140,8 @@ class Http2UpgradeHandler extends AbstractStream implements InternalHttpUpgradeH
     private volatile int lastNonFinalDataPayload;
     private volatile int lastWindowUpdate;
 
+    // Time between the "graceful" GOAWAY (max stream id) and the final GOAWAY (last seen stream id)
+    private long drainTimeout = 0;
 
     Http2UpgradeHandler(Http2Protocol protocol, Adapter adapter, Request coyoteRequest,
             SocketWrapperBase<?> socketWrapper) {
@@ -173,6 +175,8 @@ class Http2UpgradeHandler extends AbstractStream implements InternalHttpUpgradeH
 
         pingManager.initiateDisabled = protocol.getInitiatePingDisabled();
 
+        drainTimeout = protocol.getDrainTimeout();
+
         // Initial HTTP request becomes stream 1.
         if (coyoteRequest != null) {
             if (log.isTraceEnabled()) {
@@ -543,7 +547,7 @@ public void destroy() {
 
     void checkPauseState() throws IOException {
         if (connectionState.get() == ConnectionState.PAUSING) {
-            if (pausedNanoTime + pingManager.getRoundTripTimeNano() < System.nanoTime()) {
+            if (pausedNanoTime + pingManager.getRoundTripTimeNano() + drainTimeout < System.nanoTime()) {
                 connectionState.compareAndSet(ConnectionState.PAUSING, ConnectionState.PAUSED);
                 writeGoAwayFrame(maxProcessedStreamId, Http2Error.NO_ERROR.getCode(), null);
             }