--- /dev/null
+/*
+ * Copyright (c) 2024 PANTHEON.tech s.r.o. and others. All rights reserved.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v1.0 which accompanies this distribution,
+ * and is available at http://www.eclipse.org/legal/epl-v10.html
+ */
+package org.opendaylight.netconf.transport.http;
+
+import static io.netty.handler.codec.http2.HttpConversionUtil.ExtensionHeaderNames.SCHEME;
+import static io.netty.handler.codec.http2.HttpConversionUtil.ExtensionHeaderNames.STREAM_ID;
+
+import com.google.common.util.concurrent.ListenableFuture;
+import com.google.common.util.concurrent.SettableFuture;
+import io.netty.channel.Channel;
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.channel.SimpleChannelInboundHandler;
+import io.netty.handler.codec.http.FullHttpRequest;
+import io.netty.handler.codec.http.FullHttpResponse;
+import io.netty.handler.codec.http.HttpScheme;
+import io.netty.handler.ssl.SslHandler;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.atomic.AtomicInteger;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Client side {@link RequestDispatcher} implementation for HTTP 2.
+ *
+ * <p>
+ * Serves as gateway to Netty {@link Channel}, performs sending requests to server, returns server responses associated.
+ * Uses request to response mapping by stream identifier.
+ */
+class ClientHttp2RequestDispatcher extends SimpleChannelInboundHandler<FullHttpResponse> implements RequestDispatcher {
+ private static final Logger LOG = LoggerFactory.getLogger(ClientHttp2RequestDispatcher.class);
+
+ private final Map<Integer, SettableFuture<FullHttpResponse>> map = new ConcurrentHashMap<>();
+ private final AtomicInteger streamIdCounter = new AtomicInteger(3);
+
+ private Channel channel = null;
+ private boolean ssl = false;
+
+ ClientHttp2RequestDispatcher() {
+ super(true); // auto-release
+ }
+
+ private Integer nextStreamId() {
+ // identifier for streams initiated from client require to be odd-numbered, 1 is reserved
+ // see https://datatracker.ietf.org/doc/html/rfc7540#section-5.1.1
+ return streamIdCounter.getAndAdd(2);
+ }
+
+ @Override
+ public void handlerAdded(final ChannelHandlerContext ctx) throws Exception {
+ channel = ctx.channel();
+ ssl = ctx.pipeline().get(SslHandler.class) != null;
+ super.handlerAdded(ctx);
+ }
+
+ @Override
+ public ListenableFuture<FullHttpResponse> dispatch(final FullHttpRequest request) {
+ if (channel == null) {
+ throw new IllegalStateException("Connection is not established yet");
+ }
+ final var streamId = nextStreamId();
+ request.headers().setInt(STREAM_ID.text(), streamId);
+ request.headers().set(SCHEME.text(), ssl ? HttpScheme.HTTPS.name() : HttpScheme.HTTP.name());
+
+ final var future = SettableFuture.<FullHttpResponse>create();
+ channel.writeAndFlush(request).addListener(sent -> {
+ if (sent.cause() == null) {
+ map.put(streamId, future);
+ } else {
+ future.setException(sent.cause());
+ }
+ });
+ return future;
+ }
+
+ @Override
+ protected void channelRead0(final ChannelHandlerContext ctx, final FullHttpResponse response) {
+ final var streamId = response.headers().getInt(STREAM_ID.text());
+ if (streamId == null) {
+ LOG.warn("Unexpected response with no stream ID -- Dropping response object {}", response);
+ return;
+ }
+ final var future = map.remove(streamId);
+ if (future == null) {
+ LOG.warn("Unexpected response with unknown or expired stream ID {} -- Dropping response object {}",
+ streamId, response);
+ return;
+ }
+ if (!future.isDone()) {
+ // NB using response' copy to disconnect the content data from channel's buffer allocated.
+ // this prevents the content data became inaccessible once byte buffer of original message is released
+ // on exit of current method
+ future.set(response.copy());
+ } else {
+ LOG.warn("Future is already in Done state -- Dropping response object {}", response);
+ }
+ }
+}