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Thanks for the detailed response. I was aware Kubernetes has hooks for pretty much everything, so getting details on how they are used in practice is interestin

Thanks for the detailed response. I was aware Kubernetes has hooks for pretty much everything, so getting details on how they are used in practice is interesting. Mostly I'm concerned about preventing administrator mistakes; if you have enough privileges, it's distressingly easy to just accidentally delete all kinds of resources in the default configuration, especially since kubectl is context-sensitive. I like my automation software to have checks in it to prevent me from doing stupid things without explicitly disabling a number of safeties first. I feel like Kubernetes is a powertool that requires a competent and trained admin team or managed access so that you simply can't make awful mistakes as a "regular user", but a lot of the hype around it seems to be focused on how "easy" it is. To my eyes, it's indeed easy to just throw manifests from the internet at Kubernetes, but that is often akin to disabling SELinux because some blog says so; it may get things working, but it's not the competent choice most of the time. I'm also a big proponent of storing everything in git repositories, so I do like how Kubernetes enables declarative configuration, though it seems much of the tooling in the ecosystem works against that by just creating resources in a cluster with no version control...

paulfurtado 5y ago
Cool thing about finalizers is that there's no straightforward way to delete them from the CLI, you need to explicitly patch the object to delete the finalizer so that goes a long way towards preventing instant mass deletion, they really do help a lot here. The additional protection we have is via admission controllers which hook all API calls to prevent mistakes, of course, you have to foresee those mistakes and come up with a validation that prevents it. But even something as simple as "only 5 pods are allowed to be terminating at once" can help. I absolutely agree about people claiming kubernetes is easy. It is easy to throw some helm chart at the kube API and suddenly have an app running with all it's databses configured. It is hard to keep them all running. The pattern of operators seeks to solve this. Instead of a helm chart creating a MySQL statefulset, it creates a MySQLCluster that gets managed by a well-written operator following the best practices and correctly implementing all the hooks. The ecosystem is starting to converge on this finally and the beauty is that the sum of the industry's operational knowledge can be coded into these operators and we'll finally arrive at nearly fully self managing databases with backups and all. The industry isn't there quite yet though, and so at least for stateful workloads you need significant operational experience. For background: I am the Tech Lead of our team that runs the kubernetes clusters and we provide all of the primitives our users need and control access. Each database type then has dedicated teams operating them and codifying operations into operators. There is a lot of work being done. But prior to kubernetes, all of these teams separately were coding against the EC2 API with no standardization, no unified view, ad-hoc failure detection, ad-hoc auditing, etc. Kubernetes is a very substantial improvement over that, but 90% of companies never reach a scale where this is necessary. But once extremely solid open source operators exist we may truly hit the dream of just applying some self managing operator manifest to an EKS or GKE cluster and getting an actually production grade database setup. Version control is an interesting topic because it's hard to express transitive dependencies in that code. For example, the MySQL operator creating a StatefulSet and the Statefulset creating pods. It doesn't make sense to commit those lower level resources to git, they're not fully independent. However, for top level things, our build system produces artifacts from git and the deploy system creates them in the cluster. With this setup, only admins could directly apply them, which really helps with keeping things in sync with git.
- chousuke 5y ago
  I'm a bit late replying, but I just want to clarify my stance on the last paragraph; I don't think you need to store everything in the cluster in version control if they're created automatically as a result of applying the top-level configuration, If there's something important that's too dynamic to be in source control, I treat it as data to be backed up. My ideal is that what is in the repository allows me to rebuild the system from scratch (assuming suitable hardware exists) to the point where it can be successfully used as a restore target for your backups following documented restore procedures.

paulfurtado 5y ago

Cool thing about finalizers is that there's no straightforward way to delete them from the CLI, you need to explicitly patch the object to delete the finalizer so that goes a long way towards preventing instant mass deletion, they really do help a lot here. The additional protection we have is via admission controllers which hook all API calls to prevent mistakes, of course, you have to foresee those mistakes and come up with a validation that prevents it. But even something as simple as "only 5 pods are allowed to be terminating at once" can help. I absolutely agree about people claiming kubernetes is easy. It is easy to throw some helm chart at the kube API and suddenly have an app running with all it's databses configured. It is hard to keep them all running. The pattern of operators seeks to solve this. Instead of a helm chart creating a MySQL statefulset, it creates a MySQLCluster that gets managed by a well-written operator following the best practices and correctly implementing all the hooks. The ecosystem is starting to converge on this finally and the beauty is that the sum of the industry's operational knowledge can be coded into these operators and we'll finally arrive at nearly fully self managing databases with backups and all. The industry isn't there quite yet though, and so at least for stateful workloads you need significant operational experience. For background: I am the Tech Lead of our team that runs the kubernetes clusters and we provide all of the primitives our users need and control access. Each database type then has dedicated teams operating them and codifying operations into operators. There is a lot of work being done. But prior to kubernetes, all of these teams separately were coding against the EC2 API with no standardization, no unified view, ad-hoc failure detection, ad-hoc auditing, etc. Kubernetes is a very substantial improvement over that, but 90% of companies never reach a scale where this is necessary. But once extremely solid open source operators exist we may truly hit the dream of just applying some self managing operator manifest to an EKS or GKE cluster and getting an actually production grade database setup. Version control is an interesting topic because it's hard to express transitive dependencies in that code. For example, the MySQL operator creating a StatefulSet and the Statefulset creating pods. It doesn't make sense to commit those lower level resources to git, they're not fully independent. However, for top level things, our build system produces artifacts from git and the deploy system creates them in the cluster. With this setup, only admins could directly apply them, which really helps with keeping things in sync with git.

chousuke 5y ago
I'm a bit late replying, but I just want to clarify my stance on the last paragraph; I don't think you need to store everything in the cluster in version control if they're created automatically as a result of applying the top-level configuration, If there's something important that's too dynamic to be in source control, I treat it as data to be backed up. My ideal is that what is in the repository allows me to rebuild the system from scratch (assuming suitable hardware exists) to the point where it can be successfully used as a restore target for your backups following documented restore procedures.