$http occasionally fails with ERR_EMPTY_RESPONSE

We’re working on a client-server application, where the client is Angular + AngularJS hybrid, running on Chrome. The server is a spring MVC running on Tomcat.
The communication between the client and server is HTTPS.
Our client sends different REST requests to the server using the AngularJS $http service. Some of them repeat on predefined intervals.

Over the past week we started noticing that every now and then some of the repeating requests fail with ERR_EMPTY_RESPONSE (status is “failed”). For the same request it can fail and 20 seconds later (when the interval is reached) succeed.

It seems like this could potentially happen with every REST request but we mainly notice it on the repeating ones.

The failing requests seem to not reach the server at all as they don’t appear in the localhost_access_log.txt file and there is a gap between the repeating requests that did reach the server that indicate the failing requests never reached the server.

The application has been working for quite some time now and without any issues regarding $http requests until last week (around March 25th 2019).
The code that sends these REST requests is not new and has not been changed in years.
It also doesn’t look related to the latest Chrome update, as the issue reproduces with Chrome 63, and with the newest Chrome version (73).

We would appreciate your help with this issue.


Source: AngularJS