I have been running this instance of apache 2.4.17 for a long time. It is used as a proxy to a number of applications at the back. Recently I upgraded Piwik/Matomo, and it caused a bit of issue in the apache, but now it shoulbe fixed. However, after restart the physical server and apache instances numerous times, it will still crash apache pretty badly after a number of hours later, and need to apachectl restart to get it going again.
Checked apache's error.log, and there are quite a few entries like this:
[Sun Mar 21 16:15:21.126158 2021] [ssl:info] [pid 1274] [client x}:0] AH01998: Connection closed to child 28 with abortive shutdown (server <domain>:443)
[Sun Mar 21 16:15:21.136567 2021] [ssl:info] [pid 1271] [client 216.245.221.83:44352] AH01998: Connection closed to child 25 with abortive shutdown (server <domain>:443)
[Sun Mar 21 16:15:21.146466 2021] [ssl:info] [pid 1270] [client ?x}:0] AH01998: Connection closed to child 24 with abortive shutdown (server <domain>:443)
[Sun Mar 21 16:15:21.153012 2021] [ssl:info] [pid 1269] [client x}:0] AH01998: Connection closed to child 23 with abortive shutdown (server <domain>:443)
[Sun Mar 21 16:15:21.164055 2021] [ssl:info] [pid 1262] [client ?v}:0] AH01998: Connection closed to child 16 with abortive shutdown (server <domain>:443)
[Sun Mar 21 16:15:21.167462 2021] [ssl:info] [pid 1263] [client ?2):0] AH01998: Connection closed to child 17 with abortive shutdown (server <domain>:443)
[Sun Mar 21 16:15:21.169270 2021] [ssl:info] [pid 1264] [client ?x}:0] AH01998: Connection closed to child 18 with abortive shutdown (server <domain>:443)
where the client IP value is randomised... x}, ?x}, ?v} and etc.
There aren't anything strange in applications' log files.
How should I troubleshoot this problem?