keep-alive (KA) is a message sent from one device to another to check that the link between the two is operating and to prevent the link from closing abruptly.
In the context of the web server, this is also called an HTTP persistent connection, or simply HTTP keep-alive. The principle is essentially the same— to maintain the link up.
As a side note, the newer HTTP/2 protocol uses the same idea and takes it further to allow multiple concurrent requests/responses to be multiplexed over a single connection.
There are a number of advantages in making sure that the connection between the client (your customer) and the servers (your Snapt Upstreams) doesn’t cut.
- reduced latency in subsequent requests by removing the need to initiate subsequent handshakes
- reduced CPU usage and round-trips because of fewer new connections and Transport Layer Security (TLS) handshakes
- enabling HTTP pipelining of requests and responses
- reduced network congestion by having fewer TCP connections
- errors can be reported without the penalty of closing the TCP connection
How to Enable
You can enable this option on either a Group, Frontend or Backend.
Navigate accordingly to:
Balancer > Group Management
Balancer > Frontend Management
Balancer > Backend Management
Click on Edit for the Group, Frontend or Backend you want to enable
HTTP Options sub-tab > HTTP Options pane
Set the Force HTTP Close field to Server Only.
Click the Save button.
Now you have
keep-alive enabled for your Group, Frontend or Backend.
Note: global timeouts will also take effect.