How to recover from Exception caught: 500 The call failed on the server

Problem

When trying to login, application displays the following error: "Exception caught: 500 The call failed on the server".

This can happen:

1. if the browser window with the application stayed open during update
2. if the browser session has expired or
3. if database is not running.

Solution

Refresh browser (Ctrl+F5) and then log in again OR log out and log in manually. If this doesn't help, clear your browsing data and log in again.

If this method doesn't work, access the server via ssh and apply the following steps:

Linux

1. Check the status of database 
2. Start the postgresql service
3. Stop tomcat6 service
4. Start tomcat6 service (to register the application on the database)

Debian 7 / Ubuntu 14 / Centos 6

1. service postgresql-9.5 status

2. service postgresql-9.5 start

3. service tomcat6 stop

4. service tomcat6 start

Centos 7

1. systemctl status postgresql-9.5
2. systemctl start postgresql-9.5
3. systemctl stop tomcat
4. systemctl start tomcat

Debian 8 / Ubuntu 16

1. systemctl status postgresql
2. systemctl start postgresql
3. systemctl stop tomcat7
4. systemctl start tomcat7

Windows

1. Refresh browser (Ctrl+F5) and then log in again OR log out and log in manually.

If this doesn't work, do next:

1. Start the postgresql service 
   In Windows Command Prompt or PowerShell execute the following command: net start postgresql-x64-9.5
2. Restart tomcat service (to register the application on the database)
   
   1. Double click on Apache Tomcat Properties in system tray. In General tab, click Stop to stop tomcat service.
   2. Click Start to start tomcat service.