ZDM Implementing a L4 switch with Middle Tier servers
Implementing a L4 switch with Middle Tier servers
Configure Sticky Sessions
- Setup for the HTTP (80) port.
- Setup for the SSL (443) port if Zen agents access the Middle Tier server over the SSL port.
- Configure Sticky session timeouts to the same session timeout as the web server (IIS or Apache).
Configuring the L4 switch to detect if the Middle Tier server is down
- URL should return Ã¢â‚¬Å“HEAD /"status.
The Ã¢â‚¬Å“HEAD /" is the start of a HTML page so if the web server is down, then Ã¢â‚¬Å“HEAD /" will not be returned. When this happens, the L4 should set the server to a failed stated and redirect all traffic to another Middle Tier server.
Supported HTTP Protocol Error Codes by the Middle Tier
- 204 Ã¢â‚¬â€œ No Content
- 400 Ã¢â‚¬â€œ Bad Request
- 404 Ã¢â‚¬â€œ Not Found
- 500 Ã¢â‚¬â€œ Server Error
- 503 Ã¢â‚¬â€œ Out of Resources
There are other errors codes that can be implemented to help the L4 switch in detecting a server failure which depends on the needs of the customer. Certain error codes can cause more traffic or the L4 can also put the middle tier server into a bad state and forcing all traffic to a single server if implemented incorrectly. The error codes should be implemented with care.