I'm working with equipment that has a control port which allows only one active connection at a time. I have my primary client running continuously, and a standby client that is supposed to take over when the primary fails. However, I've encountered an issue where the equipment doesn't always release the control port from the primary client when it crashes. This means the standby can't connect without restarting the equipment manually. Is there a way to create a virtual socket that enables both the primary and standby clients to connect, while ensuring only one gets to connect to the equipment control port?
4 Answers
Another option could be utilizing a high-availability cluster setup like PCS (Pacemaker). It creates a floating IP that both clients can potentially use, which allows for more resilient service. The key would be ensuring your equipment can support that setup on its side.
You could also consider using HAProxy for managing your connections. It can handle TCP connections and has options for health checks to ensure the traffic is intelligently routed to the active client, helping to deal with scenarios where one of the clients goes down.
You might want to look into using a loopback interface. By assigning your host's IP to it, you can keep the connection alive even if the physical network interface fails. This technique is often used in routers to maintain stable IP addresses and could suit your needs here as well.
Loopback sounds interesting! Just to clarify, would this approach allow the standby client to take over seamlessly when the primary fails?
It sounds like the control protocol you're using might not handle connections gracefully when a client crashes. If you're using TCP, the equipment might not realize that the primary client has lost connection unless it's configured with keep-alives or similar checks. You could consider implementing a mechanism that allows you to move a shared IP address between your clients. If the standby can take over the IP of the primary when it goes down, it might help in maintaining that connection more smoothly.
That's a good point! A shared IP could reduce downtime, but as you mentioned, if the equipment doesn't actively tear down old connections, you might still run into issues. Setting up some kind of proxy could also be beneficial.
Yeah, HAProxy has some great features for this kind of redundancy! It's definitely worth exploring.