Yes, that is the problem with selective acknowledgement or "SACK". To
make the matter worse, your packet time stamps were turned off, so there
was no protection against out of sequence packets. If the client
expected acknowledgement for the TCP packet which would never come
because selective acknowledgements were turned off, that would appear as
an infinite wait. Here is a decent discussion of that parameter:
https://serverfault.com/questions/10955/when-to-turn-tcp-sack-off
On 09/18/2018 10:22 AM, Chris Taylor wrote:
Running strace on the sessions on both the db server and the php server showed the sessions just sitting in either read() or write() to the network socket and never completing.
