@Override
    public final void close(Throwable cause) {
        if (closed) {
            return;
        }
        closed = true;

        keepAliveHandler().destroy();
        if (pendingWritesMap.isEmpty()) {
            return;
        }

        for (Queue<Entry<HttpObject, ChannelPromise>> queue : pendingWritesMap.values()) {
            for (;;) {
                final Entry<HttpObject, ChannelPromise> e = queue.poll();
                if (e == null) {
                    break;
                }

                e.getValue().tryFailure(cause);
            }
        }

        pendingWritesMap.clear();
    }
The map which maps a request ID to its related pending response.
core/src/main/java/com/linecorp/armeria/internal/common/Http1ObjectEncoder.java