- some feed URLs work fine, others consistently have connection timeouts
- no errors in tt-rss logs
- curl command-line yields same results (some OK, many time out)
- curl can access the unresponsive sites by IP address; only hangs when DNS lookups needed
- non-curl tools (wget, GET, fetch) are able access all the URLs just fine
- DNS lookups with other tools (nslookup, host) are also working OK
If that describes your setup, you're probably experiencing these feed timeouts. Just upgrade to curl 7.35 or newer and you should be fine.
(On my FreeBSD system running on 13-year-old hardware, I'm in the habit of building from source and disabling IPv6 dependencies when given the option. It is probably not an issue for most people nowadays. Nevertheless, I want to share the solution in case anyone else is having problems.)
Of course, this is one of many ways feed timeouts can happen; search the forum for more!