No address associated with hostname

Hi everyone!
Since recently, after several hours of normal server functioning, file_get_contents () returns "php_network_getaddresses: getaddrinfo failed: No address associated with hostname". Nothing has been changed on the server, Google DNS are registered in the connection settings, gethostbyname () runs, everything pings from the console. At the current moment only reboot can help, but for the few hours.

OS - Ubuntu 14.04.4, hardware from https://gthost.com , web server - Nginx