A few weeks ago, we started noticing that Firefox on a Mac would present a 'Content Encoding Error' on apparently random-ish CiviCRM administration pages. They would usually be solved by reloading the page.
After running after a few white rabbits, we discovered that it was unrelated to most of the issues that the symptom might suggest [like, something related to content encoding ...], and that in fact what was happening in each case (okay, at least as far as we could tell) was a 404 on one of the page's php-generated elements, corresponding to an apparent php segfault showing up in the server logs.
If that doesn't make sense, then glad to see you're paying attention.
1. What does that generate a content encoding error?
I think that's just Firefox being stupid. It might be related to how apache hands back the response from the segfault, esp. via php-fpm. But ultimately, not my biggest concern.
2. Why are we getting segfaults that are only happening with specific client platforms?
The 404s look like they might all be angular urls, which may be behaving differently on different platforms (i.e. angular is clever enough to be doing different ajax calls for different browsers). Or maybe we're only noticing them on the platforms that handle them badly? Pretty sure no - grepping the error logs suggests they're only happening on the specific client platform (mac/firefox).
3. Why is it random-ish and non-reproducible?
Actually, there are a few specific cases where we've been able to reproduce it reliably, but it seems like there might be a caching thing that prevents it from being reliable.
Other contextual bits:
1. All Drupal 7 (well, that's because that pretty much all we're working on)
2. Mostly happening on a civi 4.7 site, but occasionally on a 4.6 site as well
3. CentOS 6 with apache 2.2 + php-fpm
4. Recently updated from php53 to ius php56u.
I increased the number of php-fpm children allowed and set a timeout and that seemed to improve, but not completely fix the issue. That suggests that a php/system issue related to memory handling.
I haven't found anything helpful on google (yeah, don't bother googling firefox's content encoding error).
Anybody got any ideas or similar experiences?