Sending a message sporadically stalls for ~10 seconds when SSL is enabled

When SSL is enabled in the NettyConnector configuration, we have sporadic stalls for 10 seconds in message sends. The number of stalls seem to depend on the current workload. We have seen it happening multiple times per minute, but other cases with only a few stalls per hour.

Every time we have a stall, there is also this log entry in the server logfile:
AMQ212040: Timed out waiting for netty ssl close future to complete