title: 503 Service Unavailable error Apache Tomcat
body: <p>I try to deploy my Java project Apache Tomcat server but sometimes it gets down and returns me this page</p>
  
  <p><a href="https://i.stack.imgur.com/vMhuI.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/vMhuI.png" alt="service unavailable 503"></a></p>
  
  <p>Tomcat is installed on the <a href="http://digitalocean.com" rel="nofollow noreferrer">Digitalocean's</a> Ubuntu 14.04 and droplet's properties are 512Mb/1CPU, 20GB SSD Disk, 1000 GB transfer. I took the lowest option for test purposes. The site is visited by nobody except me and from the graphs I observe that the server is not overloaded at all. Most of the time everything works fine until suddenly the server returns 503. After I restart it keeps working fine again till the next 503 error in several days. I'd like to know what could cause this error: my mistake on configuring the server or maybe problems on server side?</p>