Http2ControlFrameLimitEncoder Class — netty Architecture

Source Code

codec-http2/src/main/java/io/netty/handler/codec/http2/Http2ControlFrameLimitEncoder.java lines 30–108

final class Http2ControlFrameLimitEncoder extends DecoratingHttp2ConnectionEncoder {
    private static final InternalLogger logger = InternalLoggerFactory.getInstance(Http2ControlFrameLimitEncoder.class);
    private int outstandingControlFrames;

    private final int maxOutstandingControlFrames;
    private final ChannelFutureListener outstandingControlFramesListener = f-> outstandingControlFrames--;
    private Http2LifecycleManager lifecycleManager;
    private boolean limitReached;

    Http2ControlFrameLimitEncoder(Http2ConnectionEncoder delegate, int maxOutstandingControlFrames) {
        super(delegate);
        this.maxOutstandingControlFrames = ObjectUtil.checkPositive(maxOutstandingControlFrames,
                "maxOutstandingControlFrames");
    }

    @Override
    public void lifecycleManager(Http2LifecycleManager lifecycleManager) {
        this.lifecycleManager = lifecycleManager;
        super.lifecycleManager(lifecycleManager);
    }

    @Override
    public ChannelFuture writeSettingsAck(ChannelHandlerContext ctx, ChannelPromise promise) {
        ChannelPromise newPromise = handleOutstandingControlFrames(ctx, promise);
        if (newPromise == null) {
            return promise;
        }
        return super.writeSettingsAck(ctx, newPromise);
    }

    @Override
    public ChannelFuture writePing(ChannelHandlerContext ctx, boolean ack, long data, ChannelPromise promise) {
        // Only apply the limit to ping acks.
        if (ack) {
            ChannelPromise newPromise = handleOutstandingControlFrames(ctx, promise);
            if (newPromise == null) {
                return promise;
            }
            return super.writePing(ctx, ack, data, newPromise);
        }
        return super.writePing(ctx, ack, data, promise);
    }

    @Override
    public ChannelFuture writeRstStream(
            ChannelHandlerContext ctx, int streamId, long errorCode, ChannelPromise promise) {
        ChannelPromise newPromise = handleOutstandingControlFrames(ctx, promise);
        if (newPromise == null) {
            return promise;
        }
        return super.writeRstStream(ctx, streamId, errorCode, newPromise);
    }

    private ChannelPromise handleOutstandingControlFrames(ChannelHandlerContext ctx, ChannelPromise promise) {
        if (!limitReached) {
            if (outstandingControlFrames == maxOutstandingControlFrames) {
                // Let's try to flush once as we may be able to flush some of the control frames.
                ctx.flush();
            }
            if (outstandingControlFrames == maxOutstandingControlFrames) {
                limitReached = true;
                Http2Exception exception = Http2Exception.connectionError(Http2Error.ENHANCE_YOUR_CALM,
                        "Maximum number %d of outstanding control frames reached", maxOutstandingControlFrames);
                logger.info("{} Maximum number {} of outstanding control frames reached, closing channel.",
                        ctx.channel(), maxOutstandingControlFrames, exception);

                // First notify the Http2LifecycleManager and then close the connection.
                lifecycleManager.onError(ctx, true, exception);
                ctx.close();
            }
            outstandingControlFrames++;

            // We did not reach the limit yet, add the listener to decrement the number of outstanding control frames
            // once the promise was completed
            return promise.unvoid().addListener(outstandingControlFramesListener);
        }
        return promise;
    }
}