Hello! Have you ever attempted to operate an app across multiple VPS servers? This can be a complicated process. Suddenly users can not stay logged in, and their sessions gone. Have you ever wondered why larger applications can manage one thousand of users easily while smaller apps have difficulty with even eight? The answer has to do with managing sessions correctly.
Really annoying, right?
Central Session Stores
We are using some sort of central database or central cache like Redis or Memcached to persist all session data. Each VPS servers can read from a central file that would keep any user logged in regardless of which one they hit.
Sticky Sessions
Some load balancers will support sticky sessions. This means that a user will have the same server every time they visit. Sticky sessions are easy, but are not optimal if that one server becomes overloaded.
JWT Tokens
Another option is stateless sessions using JWT tokens, where the client has a signed token and the server does not store the session state. This works well for applications and APIs but requires caution when managing the tokens for security.
It's satisfying to watch users operate within your application and not be encumbered by logging in or logging out issues. Once you understand sessions, your app scales easily and reliably and you don't have to worry about losing sessions.
Why Sessions Matter
When you have one server it is easy to manage sessions. The server knows who is logged in, and the server stores temporary data. When you have more than one server, it is possible that any of those servers do not share the same information with the other servers. Imagine logging in on one server, and then your next request is sent to the other server; you are suddenly logged out.Really annoying, right?
Ways to Store Sessions
We can fix this in so many ways, but here are some simple ways.Central Session Stores
We are using some sort of central database or central cache like Redis or Memcached to persist all session data. Each VPS servers can read from a central file that would keep any user logged in regardless of which one they hit.
Sticky Sessions
Some load balancers will support sticky sessions. This means that a user will have the same server every time they visit. Sticky sessions are easy, but are not optimal if that one server becomes overloaded.
JWT Tokens
Another option is stateless sessions using JWT tokens, where the client has a signed token and the server does not store the session state. This works well for applications and APIs but requires caution when managing the tokens for security.
Experience-Based Tips
- Monitor session performance. You do not want users getting logged out in the middle of logging in.
- If the session is sensitive, encrypt it.
- Timeouts set inappropriately can be detrimental. If the timeout is too short, the user accounts will get logged out too soon. If it is too long, the servers use excessive memory.
Final Thoughts
Running an app across several virtual private server machines (VPS) is not only about the added power available, but it is also knowing how to manage session effectively. Centralized stores, sticky sessions, and JWT’s all have varying positives and negatives. Often, finding a solution that is a blend of all three will offer the highest success.It's satisfying to watch users operate within your application and not be encumbered by logging in or logging out issues. Once you understand sessions, your app scales easily and reliably and you don't have to worry about losing sessions.