5 ms·

Please, do not manage deployments with imperative kubectl commands, I beg of you.

by sgarland 4y ago

I_dev_outdoors 4y ago
I probably wouldn't do this, but what problem does this cause?
- ryapric 4y ago
  The same problems any imperative management within declarative config causes -- drift. If the tool you're using supports declarative configuration, all changes should be made exclusively via the declarative interface to prevent that drift. In this example, the new image should be added to the original manifest itself, not via a CLI update.
  - throwaway894345 4y ago
    It depends on how you manage your changes. A lot of people don't have their infra-as-code manage the deployment's image field--rather, that's updated by the application's CD pipeline. There's no drift to worry about.
    - xbar 4y ago
      So upon deploy the CD pipeline calls kubectl with the proper deployment image and that's ok?
      - throwaway894345 4y ago
        Yes.
- sgarland 4y ago
  Drift, as the other child comment mentions, but also loss of version control. I do not want to have to trawl through someone's shell history to figure out what they changed, nor do I want to have to redirect `kubectl get foo -o yaml` output into diff. If everything is in code, and you have a reasonable branching strategy, it's much easier to control change, to rollback bad merges, to run pre-hooks like security checks and configuration validation tools, etc.
  - thinkmassive 4y ago
    You know kubectl has a built in diff subcommand?
    - sgarland 4y ago
      I do now! Thank you.
  - throwaway894345 4y ago
    It's not drift, because the infra-as-code doesn't manage the image field (the application's CD pipeline does). You don't trawl through someone's shell history', you look at the CD pipeline history. Rollbacks are easy--you just deploy the prior version via your CD tool. I think you're assuming that invoking kubectl means invoking it directly from a user's command line, but kubectl can also be called in a CD script.
    - sgarland 4y ago
      If you're using ArgoCD or something then sure, but bear in mind the original statement you made was directed at someone who is new to K8s, and given a command that can be executed from their shell, they would likely assume that's what you meant.
      - throwaway894345 4y ago
        It doesn’t have to be Argo, it can be Jenkins. Whether or not you use a CD pipeline is orthogonal to whether or not you use k8s. The best practice is to use a pipeline whether you’re targeting k8s or bare VMs or a higher level PaaS abstraction.
      - I_dev_outdoors 4y ago
        I'm not new to Kubernetes and I've been using containers since Solaris zones were introduced.
- alias_neo 4y ago
  The declarative approach is a more sustainable way to run Kubernetes. If you define some desired state in manifests and apply them to a cluster, they can be applied again to new clusters or the same one and Kubernetes will attempt to maintain the desired state. This state can be version controlled, written in stone, whatever you prefer and it can always be attained. When administrators start issuing imperative commands to a cluster, state starts being changed and there is no record[0] of the state Kubernetes is being asked to maintain. [0] Not entirely true, the state can always be retrieved from the cluster so long as it hasn't failed.
  - jen20 4y ago
    I find this to be a common misconception, stemming from a misunderstanding of what "declarative" means (especially common when people are discussing tools like Terraform). Firstly as you point out, there is a record of the state Kubernetes is being asked to maintain: it's in the API server as the spec of each resource. Secondly, using `kubectl` "patch" in the manner described is not making changes to the cluster state directly, it's making changes to the specification of what should be maintained, and the various controllers effect the state changes. Fundamentally, the argument seems to come down to "you don't have a record of what you once asked the API server to do", and that's fair enough - you don't. But that has nothing to do with imperative or declarative models. I'm not advocating actually doing this on a day-to-day basis, but the arguments against it are not ones of imperative vs declarative.
    - sgarland 4y ago
      Given that Kubernetes' docs[0] discuss using imperative commands, I think it's a fairly reasonable way to describe it. [0] https://kubernetes.io/docs/tasks/manage-kubernetes-objects/imperative-command/ https://kubernetes.io/docs/tasks/manage-kubernetes-objects/i...
      - throwaway894345 4y ago
        Why is applying a full manifest “declarative” but applying a patch is “imperative”? That’s clearly an error.
mihaigalos 4y ago
Spot on!
throwaway894345 4y ago
This is a declarative kubectl command.
- sgarland 4y ago
  Kubernetes' docs[0] disagree. [0] https://kubernetes.io/docs/tasks/manage-kubernetes-objects/imperative-command/#how-to-update-objects https://kubernetes.io/docs/tasks/manage-kubernetes-objects/i...
  - throwaway894345 4y ago
    They’re not being precise with their language. Applying a full manifest is no more “declarative” than applying a patch.
- deleted 4y ago
  [deleted]
jrx 4y ago
The question is: what tool to use? I'm a solo developer running a very small kube cluster for my hobby project. I very much wanted to have a declarative version controlled state of my cluster. Every time I try googling solutions I get flooded with some enterprise Saas offerings that do nothing I want. I managed my stateful sets/services for a while with terraform, but my experience was absolutely terrible and I have stopped that eventually. I now use "kubectl patch" and "kubectl apply" with handwritten yaml, but the workflow feels very clunky. Intuitively it seems obvious to me that there must be a tool helping with that, but for some reason I was absolutely not able to find anything that would be even a little bit helpful. I am considering writing a couple python scripts that will automate it.
- edude03 4y ago
  Fluxcd, or argo CD if you want a nice UI
- lukeschlather 4y ago
  I'm a fan of emrichen, but simple text templating (Jinja) works almost as well. (j2cli means you can just provide a yaml file with per-stage configs.)
- kube-system 4y ago
  kubectl apply on a directory full of yaml works fairly well for small stuff. Check it into git and it's version controlled. If you need something more flexible than that, try making your own helm chart. Helm will give you some text templating, pre and post hooks, some basic functions, and some versioning and rollback functionality. You can start simple by just pasting in your existing k8s yaml, and then just pull out the pieces you need into variables in your values file. If you need to change an image version, then you just update the variable and `helm upgrade mychart ./mychart`
  - throwaway894345 4y ago
    kubectl apply on a directory doesn’t work because deleting a resource manifest won’t delete the corresponding resources.

Please, do not manage deployments with imperative kubectl commands, I beg of you.

I_dev_outdoors 4y ago

I probably wouldn't do this, but what problem does this cause?

ryapric 4y ago
The same problems any imperative management within declarative config causes -- drift. If the tool you're using supports declarative configuration, all changes should be made exclusively via the declarative interface to prevent that drift. In this example, the new image should be added to the original manifest itself, not via a CLI update.
- throwaway894345 4y ago
  It depends on how you manage your changes. A lot of people don't have their infra-as-code manage the deployment's image field--rather, that's updated by the application's CD pipeline. There's no drift to worry about.
  - xbar 4y ago
    So upon deploy the CD pipeline calls kubectl with the proper deployment image and that's ok?
    - throwaway894345 4y ago
      Yes.
sgarland 4y ago
Drift, as the other child comment mentions, but also loss of version control. I do not want to have to trawl through someone's shell history to figure out what they changed, nor do I want to have to redirect `kubectl get foo -o yaml` output into diff. If everything is in code, and you have a reasonable branching strategy, it's much easier to control change, to rollback bad merges, to run pre-hooks like security checks and configuration validation tools, etc.
- thinkmassive 4y ago
  You know kubectl has a built in diff subcommand?
  - sgarland 4y ago
    I do now! Thank you.
- throwaway894345 4y ago
  It's not drift, because the infra-as-code doesn't manage the image field (the application's CD pipeline does). You don't trawl through someone's shell history', you look at the CD pipeline history. Rollbacks are easy--you just deploy the prior version via your CD tool. I think you're assuming that invoking kubectl means invoking it directly from a user's command line, but kubectl can also be called in a CD script.
  - sgarland 4y ago
    If you're using ArgoCD or something then sure, but bear in mind the original statement you made was directed at someone who is new to K8s, and given a command that can be executed from their shell, they would likely assume that's what you meant.
    - throwaway894345 4y ago
      It doesn’t have to be Argo, it can be Jenkins. Whether or not you use a CD pipeline is orthogonal to whether or not you use k8s. The best practice is to use a pipeline whether you’re targeting k8s or bare VMs or a higher level PaaS abstraction.
    - I_dev_outdoors 4y ago
      I'm not new to Kubernetes and I've been using containers since Solaris zones were introduced.
alias_neo 4y ago
The declarative approach is a more sustainable way to run Kubernetes. If you define some desired state in manifests and apply them to a cluster, they can be applied again to new clusters or the same one and Kubernetes will attempt to maintain the desired state. This state can be version controlled, written in stone, whatever you prefer and it can always be attained. When administrators start issuing imperative commands to a cluster, state starts being changed and there is no record[0] of the state Kubernetes is being asked to maintain. [0] Not entirely true, the state can always be retrieved from the cluster so long as it hasn't failed.
- jen20 4y ago
  I find this to be a common misconception, stemming from a misunderstanding of what "declarative" means (especially common when people are discussing tools like Terraform). Firstly as you point out, there is a record of the state Kubernetes is being asked to maintain: it's in the API server as the spec of each resource. Secondly, using `kubectl` "patch" in the manner described is not making changes to the cluster state directly, it's making changes to the specification of what should be maintained, and the various controllers effect the state changes. Fundamentally, the argument seems to come down to "you don't have a record of what you once asked the API server to do", and that's fair enough - you don't. But that has nothing to do with imperative or declarative models. I'm not advocating actually doing this on a day-to-day basis, but the arguments against it are not ones of imperative vs declarative.
  - sgarland 4y ago
    Given that Kubernetes' docs[0] discuss using imperative commands, I think it's a fairly reasonable way to describe it. [0] https://kubernetes.io/docs/tasks/manage-kubernetes-objects/imperative-command/ https://kubernetes.io/docs/tasks/manage-kubernetes-objects/i...
    - throwaway894345 4y ago
      Why is applying a full manifest “declarative” but applying a patch is “imperative”? That’s clearly an error.

mihaigalos 4y ago

Spot on!

throwaway894345 4y ago

This is a declarative kubectl command.

sgarland 4y ago
Kubernetes' docs[0] disagree. [0] https://kubernetes.io/docs/tasks/manage-kubernetes-objects/imperative-command/#how-to-update-objects https://kubernetes.io/docs/tasks/manage-kubernetes-objects/i...
- throwaway894345 4y ago
  They’re not being precise with their language. Applying a full manifest is no more “declarative” than applying a patch.
deleted 4y ago
[deleted]

jrx 4y ago

The question is: what tool to use? I'm a solo developer running a very small kube cluster for my hobby project. I very much wanted to have a declarative version controlled state of my cluster. Every time I try googling solutions I get flooded with some enterprise Saas offerings that do nothing I want. I managed my stateful sets/services for a while with terraform, but my experience was absolutely terrible and I have stopped that eventually. I now use "kubectl patch" and "kubectl apply" with handwritten yaml, but the workflow feels very clunky. Intuitively it seems obvious to me that there must be a tool helping with that, but for some reason I was absolutely not able to find anything that would be even a little bit helpful. I am considering writing a couple python scripts that will automate it.

edude03 4y ago
Fluxcd, or argo CD if you want a nice UI
lukeschlather 4y ago
I'm a fan of emrichen, but simple text templating (Jinja) works almost as well. (j2cli means you can just provide a yaml file with per-stage configs.)
kube-system 4y ago
kubectl apply on a directory full of yaml works fairly well for small stuff. Check it into git and it's version controlled. If you need something more flexible than that, try making your own helm chart. Helm will give you some text templating, pre and post hooks, some basic functions, and some versioning and rollback functionality. You can start simple by just pasting in your existing k8s yaml, and then just pull out the pieces you need into variables in your values file. If you need to change an image version, then you just update the variable and `helm upgrade mychart ./mychart`
- throwaway894345 4y ago
  kubectl apply on a directory doesn’t work because deleting a resource manifest won’t delete the corresponding resources.