I'm upgrading a client to FMS 15 from 13. The solution uses WebDirect. The server is a 2012 mac mini running OS X, 10.11.6, 16GB of RAM on a SSD.
Access from FileMaker is ok. WebDirect access is extremely slow on the LAN using various client machines. Sometimes I'm getting this error when loading the file in the latest Safari or Chrome.
Failed to load the widgetset: ./VAADIN/widgetsets/com.filemaker.jwpc.iwp.widgetset.UIWidgetSet/com.filemaker.jwpc.iwp.widgetset.UIWidgetSet.nocache.js?1495047222768
Sometimes the file eventually does allow login. The page elements are often missing style info and performance continues to be extremely slow. Admin console shows that the Web Publishing Engine is turning off sometimes. No alerts appear in the server logs when this happens. Nothing seems amiss in the performance graphs.
So far I've done several clean installs including renaming the FileMaker Server folder and making a new one. I've tried FMS 15.0.1 and updating to 15.0.3.
Currently, the slow performance is painfully obvious after a clean install, opening the Sample File with no other databases, plugins or SSL cert installed. It takes several minutes just for the WebDirect Home Page to appear.
The old FileMaker 13 server is still installed on the second server drive. When I reboot to that drive, WebDirect performance is normal, so I'm not expecting a network issue.