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We run stateful apps on Kubernetes. There are obvious rough areas (the lack of persistent volume resizing, for example, which is scheduled for 1.11), but overal

We run stateful apps on Kubernetes. There are obvious rough areas (the lack of persistent volume resizing, for example, which is scheduled for 1.11), but overall, it's great. What a lot of naysayers leave out, or choose to ignore, is that the challenges running stateful apps on Kubernetes mirror those of running stateful apps anywhere. If you run Postgres on a VM, for example, you're completely reliant on that VM staying up -- this is no different from Kubernetes. Some will also point out the dangers of co-locating lots of software (such as Postgres) on the same machine as many other containers, as they will compete for CPU and I/O; but this is also no different than on Kubernetes, which provides plenty of tools (affinities/anti-affinities, node selectors) to isolate containers to machines. And so on. Containers bring some new challenges, but Kubernetes meets them quite well. What specific issues do you have? I'm not sure I understand the point about routing. I also don't understand what the "pain" of stateful sets refers to.

FBISurveillance 8y ago
The the original commenter but I'll jump in: 1. While "we already rely on VM staying up", with k8s we reply on both VM staying up and kubernetes infra on top of that VM staying UP 2. Maintaining a complex stateful system on k8s _requires_ having and maintaining an operator for that system. 3. You reduce your options when it comes to tweaking systems, e.g. local SSDs on GCP are available in SCSI and NVMe flavors, while GKE supports only SCSI; harder to perform fine-tuning and other tasks on the underlying VMs that would have been trivial with Chef or similar. 4. Enterprise systems like Splunk explicitly mention that their support does not cover Splunk clusters running on kubernetes. 5. As mentioned, you can't even resize a disk without going through dance of operations that would take days or weeks when you're working something like Kafka at scale. 6. Some stateful services like Zookeeper require stable identities and this is far from perfect on kubernetes. 7. More complex traffic routing that involves additional fees because to achieve (6) you sometimes need to expose things publicly. That's just from the top of my head. Disclaimer: We run 10+ stateful services on Kubernetes.

FBISurveillance 8y ago

The the original commenter but I'll jump in: 1. While "we already rely on VM staying up", with k8s we reply on both VM staying up and kubernetes infra on top of that VM staying UP 2. Maintaining a complex stateful system on k8s _requires_ having and maintaining an operator for that system. 3. You reduce your options when it comes to tweaking systems, e.g. local SSDs on GCP are available in SCSI and NVMe flavors, while GKE supports only SCSI; harder to perform fine-tuning and other tasks on the underlying VMs that would have been trivial with Chef or similar. 4. Enterprise systems like Splunk explicitly mention that their support does not cover Splunk clusters running on kubernetes. 5. As mentioned, you can't even resize a disk without going through dance of operations that would take days or weeks when you're working something like Kafka at scale. 6. Some stateful services like Zookeeper require stable identities and this is far from perfect on kubernetes. 7. More complex traffic routing that involves additional fees because to achieve (6) you sometimes need to expose things publicly. That's just from the top of my head. Disclaimer: We run 10+ stateful services on Kubernetes.