I'm trying to create an active/passive cluster in GCP, and I'm looking at using the native load balancer to achieve this.
For example, I want the load balancer to only forward traffic to a particular set of nodes (the standby nodes) only if the main set of nodes (the active nodes) fails the health check.
I would have thought this would be possible, but I can't see any option which would allow me to achieve this. From what I can tell, only round robin load balancing is possible, or am I missing something?
Google Cloud Load Balancer Active/Standby Decisions
clustergoogle-cloud-platformgoogle-compute-engineload balancing
Related Solutions
When you create a Rackspace Cloud Load Balancer you configure the protocol and port to be balanced:
Now you need to edit the configuration to support your new protocol (HTTPS). You have a couple of options:
Serving HTTPS directly from the servers
If you are serving HTTPS on port 443 from the servers themselves and just using the LB to pass the traffic, rather than offloading SSL to the LB, you need to edit the load balancer to use that port and protocol.
You should also look at your node list for the node IP addresses and test from one node to the other to make sure your site is indeed reachable on the expected port.
Serving HTTPS from the Load Balancer
If instead of hosting your certificate directly on your servers you want to host it on the LB, set your protocol on the LB back to HTTP on port 80, and edit the Secure Traffic (SSL) setting in Optional Features:
Your load balancer will cost a bit more if you do this, but it may also serve to solve your issue if you are having trouble configuring your servers to serve HTTPS over port 443 directly.
health checks managed instance groups VS health checks load balancing
The health checks used by managed instance groups are the same health checks used by load balancing, with some differences in behavior. Health checks that you apply to load balancing services help a load balancer determine where to direct network traffic. These health checks do not cause Compute Engine to recreate instances. Health checks that you apply to managed instance groups will proactively signal to the managed instance group to delete and recreate instances if they become UNHEALTHY.
For the majority of scenarios, use separate health checks for load balancing and for monitoring managed instance groups. Health checking for load balancing can and should be more aggressive since these health checks determine whether an instance receives user traffic. Since customers might rely on your services, you want to catch non-responsive instances quickly so you can redirect traffic if necessary. In contrast, health checking for instance groups will cause Compute Engine proactively replace failing instances so you could create health checks that are more conservative than health checks for a load balancer.
Best Answer
Round robin load-balancing is used only for compute instances with in the same Managed Instance Group(MIG). If you want to have control over balancing modes, you need to put the active and passive nodes in separate nodes and regions/zones. Again, why bother with activie/passive nodes, when you can make your active nodes highly available by deploying them across multiple zones and regions? The GLB will pick the healthy active nodes.
If you think you still need active/passive nodes, as far as I know, GCP doesn't provide the exact feature you are asking, but I think you might get close by tweaking the
balancingModeandcapacity settingproperty of the GLB backend services resource. For instance, you can set the cpu utilization and capacity of standby nodes to almost zero(but not zero) and set it to 100% on active nodes. This way, the load balancer will send all or most of traffic to active nodes, only when active nodes fail, it will route traffic to passive nodes. Since GLB is also geo-based, you might put your active nodes in a MIG closer to the clients.Reference - Google global HTTP load balancer documentation