• Terraform output values

  2 min read

  
  

  To be able to save data generated using terraform to be able to import the terraform state somewhere else using terraform_remote_state or retrieving it using the CLI we need to use the output directive:

  output "alb_dns_name" {
    description = "ALB DNS name"
    value       = aws_alb.jenkins-alb.dns_name
  }
  

  16/04/2021

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• JVM heap options: Xmx and Xms

  2 min read

  The Xmx and Xms settings are most commonly overlooked settings but yet quite critical for the JVM to perform as expected. They control the JVM's heap: the memory area where objects are instantiated.

  15/04/2021

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• kubectl drain: prepare node for maintenance

  2 min read

  
  

  You can use kubectl drain to evict pods from a node and mark it as unschedulable to prevent new pods from get created on this node. It will allow the pod's containers to gracefully terminate, respecting the PodDisruptionBudgets with a few exceptions. Let's test it suing the following nodes:

  $ kubectl get nodes
  NAME                    STATUS   ROLES                  AGE   VERSION
  nauvoo.pet2cattle.com   Ready    control-plane,master   19d   v1.20.4+k3s1
  tycho.pet2cattle.com    Ready    <none>                 26s   v1.20.4+k3s1
  

  14/04/2021

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• How kubernetes hides away the volumeMounts complexity

  4 min read

  
  

  If we try compare volumeMounts with the actual mounts that we have on a pod using, for example, df it can be quite confusing due to the usage of the overlay filesystem

  Let's consider the volumeMounts section of a deploy:

  $ kubectl get deploy pet2cattle -o yaml
  (...)
            volumeMounts:
            - mountPath: /opt/pet2cattle/conf
              name: config
            - mountPath: /opt/pet2cattle/data
              name: pet2cattle
              subPath: data
            - mountPath: /opt/pet2cattle/lib
              name: pet2cattle
              subPath: lib
            - mountPath: /tmp
              name: tmp-dir
  (...)
  

  And compare it with the filesystem we see on the pod:

  $ kubectl exec pet2cattle-8475d6697-jbmsm -- df -hP
  Filesystem      Size  Used Avail Use% Mounted on
  overlay         100G  9.7G   91G  10% /
  tmpfs            64M     0   64M   0% /dev
  tmpfs           3.9G     0  3.9G   0% /sys/fs/cgroup
  /dev/xvda1      100G  9.7G   91G  10% /tmp
  shm              64M     0   64M   0% /dev/shm
  /dev/xvdcu       20G  2.5G   18G  13% /opt/pet2cattle/lib
  tmpfs           3.9G   12K  3.9G   1% /run/secrets/kubernetes.io/serviceaccount
  tmpfs           3.9G     0  3.9G   0% /proc/acpi
  tmpfs           3.9G     0  3.9G   0% /proc/scsi
  tmpfs           3.9G     0  3.9G   0% /sys/firmware
  

  13/04/2021

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• Inspecting resources on the terraform state

  1 min read

  While debugging an issue it can be quite handy to be able to inspect the terraform state. We can inspect specific resources by using terraform state show

  12/04/2021

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• find and findstr: grep for Windows

  2 min read

  On a Windows server there's also a way of fitering other command's output just like you would do using grep on a Linux: You can do it using find and findstr

  09/04/2021

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• DynamoDB table for state locking and consistency checking on terraform

  2 min read

  
  

  When using a remote terraform state with S3, it is recomended to use a dynamoDB table for:

  • State locking: Ensures the terrafrom state it is not being modified by two threads at the same time
  • Consistency checking: Makes sure that that terraform it's being used it is the one that it is expected to be used

  For example:

  terraform {
    backend "s3" {
      bucket         = "infra-tfstate"
      key            = "jenkins/terraform.tfstate"
      region         = "eu-west-1"
      dynamodb_table = "terraform_locks"
    }
  }
  

  08/04/2021

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• Terraform error: Provider configuration not present

  2 min read

  Due to the need to use the count keyword for making a resource optional I wanted to upgrade from terraform 0.12 to 0.13 but while doing so I found the following error:

  Error: Provider configuration not present
  
  To work with module.jenkins.aws_iam_policy.jenkins_policy
  its original provider configuration at provider["registry.terraform.io/-/aws"]
  is required, but it has been removed. This occurs when a provider
  configuration is removed while objects created by that provider still exist in
  the state. Re-add the provider configuration to destroy
  module.jenkins.aws_iam_policy.jenkins_policy, after which
  you can remove the provider configuration again.
  

  07/04/2021

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• AWS CLI configuration for assuming a different role

  2 min read

  On a previous post we saw how to test we can assume a role using AWS CLI but how can we configure AWS CLI to assume an specific role before performing some request? We can do it using a profile to save us from the trouble of having to change three different environment variables.

  06/04/2021

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• k3s: Join a new worker node to an existing cluster

  3 min read

  
  

  On a previous post we saw how ridiculously easy is to bootstrap a k3s cluster on a Raspberry Pi but what do we need to do to join new worker nodes to the cluster?

  05/04/2021

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