• Kubernetes: Search the specific rule granting a given permission

  2 min read

  
  

  Sometimes might be difficult to tell how some subject (User, ServiceAccount, ...) is able to perform a certain task: What's the Role or ClusterRole granting some permission?

  For this we can use the searchrule plugin.

  25/07/2023

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• Monitoring APIRequestCount in OpenShift

  2 min read

  
  

  Openshift provides an object that tracks the number of requests made to the Kubernetes API server. It provides insights into the load on the cluster, the performance of applications, and helps in capacity planning. By monitoring APIRequestCount, you can identify potential bottlenecks, detect unusual spikes in traffic, and optimize resource allocation.

  $ kubectl get apirequestcounts
  NAME                                                                           REMOVEDINRELEASE   REQUESTSINCURRENTHOUR   REQUESTSINLAST24H
  alertmanagerconfigs.v1alpha1.monitoring.coreos.com                                                6                       1706
  alertmanagers.v1.monitoring.coreos.com                                                            20                      2891
  apiservices.v1.apiregistration.k8s.io                                                             994                     99521
  (...)
  

  11/07/2023

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• Kubernetes: Configuring Topology Spread Constraints to tune Pod scheduling

  2 min read

  
  

  Ensuring high availability and fault tolerance in a Kubernetes cluster is a complex task: One important feature that allows us to addresses this challenge is Topology Spread Constraints.

  10/07/2023

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• OpenShift 3.11 - custom default route certificate failing with certificate has expired or is not yet valid

  2 min read

  
  

  After trying to set a custom default certificate for the OpenShift routes we might see how it's Pods starts crashing:

  $ kubectl get pods
  NAME                          READY   STATUS             RESTARTS   AGE
  router-10-rh8vf               1/1     Running            0          32m
  router-10-f2dt2               0/1     CrashLoopBackOff   6          7m
  router-10-m45b7               1/1     Running            0          31m
  

  Checking it's logs we'll get a quite misleading message:

  $ kubectl logs router-10-f2dt2 -n default
  Error from server: Get https://some.openshift.cluster:10250/containerLogs/default/router-10-f2dt2/router: x509: certificate has expired or is not yet valid
  

  04/07/2023

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• Using Abbreviated Commits in Git

  1 min read

  
  

  To pin some code to a specific version we can use a commit ID instead of a tag but using such a long string might feel a tad cumbersome:

  $ git log
  commit fb944d599d5487229463478928834cac20963f75 (HEAD -> main)
  Author: Eric <some@thing.com>
  Date:   Wed Jun 7 20:27:17 2023 +0100
  
      Fix exit with no error when cert violates lookahead (#2395)
  
  (...)
  

  22/06/2023

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