I noticed some TCP_MISS/000 entries in Squid access_log this afternoon, as what I saw 3 years ago.
As we know that TCP_MISS means the URL has no stored objects in cache, and TCP_MISS/000 is the bit usually means aborted, indicating there’s no reply to the request before the client aborted the connection.
It might be caused by the following reasons:
1, The client aborted request before SQUID could return any data.
2, The website might be unavailable, due to DNS issue, network issue or an abnormal running web server.
For DNS issues, we need to check whether the dns server that used by SQUID is working as expected or not.
For network issues, we might need to check network connection status, packet lost, transfer latency or something else.
To check a web server, you can send some command to its service port, usually, you can follow this command:
$ telnet Your.Server.tld 80 [return]
GET / HTTP/1.0 [return][return]
If there is no output, you might need to restart the web server.