This problem shows up when I have poor WiFi connectivity, or no WiFi. I’m using my android phone, with chrome browser, to connect to my website (LAMP), and limping along with poor response, but happy and productive. But then I can’t reach the website at all. I can reach other websites but not my website. I’ve tried closing my chrome and reopening it. If I wait several minutes I can usually get back to my website. However, my application is time-critical and this delay is very disruptive. I’ve found that when I can’t get through on chrome, if I immediately switch to the Samsung browser (also chromium-based) I can regain access to the my website right away. Then after several minutes, I might lose access again. I can immediately regain access if I switch back to chrome. So the problem is not chrome itself. Perhaps if I had 2 instances of chrome, say chrome and chrome-beta, I could switch between those successfully. But I haven’t tried that experiment. In long sessions, with very bad connectivity, I have to switch browsers about every 5 minutes.
It seems like the bad connectivity causes Apache to temporarily ignore me. Perhaps some mechanism whereby the socket (or some other intermediate-entity, like a PHP worker) is marked "bad" but not closed. So that intermediate-entity has to timeout before the same browser can connect again. Perhaps by switching browsers, a new intermediate-entity is opened and the old one abandoned. I’m just guessing at a possible mechanism.
I’ve looked at apache error log, apache access log, php error log and php-fpm error log. I don’t see anything that coincides with my connectivity problem. My php max_execution_time is set to 120. I’m not hitting that as far as I can tell.