You are browsing a read-only backup copy of Wikitech. The live site can be found at

Kubernetes: Difference between revisions

From Wikitech-static
Jump to navigation Jump to search
m (→‎Add a new service: Add sudo -i for checkig namespace creation)
Line 34: Line 34:

=== Add a new service ===
=== Add a new service ===
To add a new service named '''service-foo''' to the clusters of the '''main''' group:
Documentation on how to deploy a new service can be found at [[Kubernetes/Add_a_new_service]]
#Ensure the service has its ports registered at: [[Service ports]]
#Create deployment user/tokens in the puppet private and public repos (public repo means 'labs/private').  You can use a randomly generated 22-character [A-z0-9] password for each of the two required tokens. You need to edit the <code>hieradata/common/profile/kubernetes.yaml</code> file in the private repository - specifically the <code>profile::kubernetes::infrastructure_user</code> key, as in the example below:<syntaxhighlight lang="yaml">
      token: <REDACTED>
      groups: [system:masters]
+    service-foo:
+      token: <YOUR_TOKEN>
+      groups:
+        - deploy
+    service-foo-deploy:
+      token: <ANOTHER_TOKEN>
</syntaxhighlight>The additional user with the -deploy suffix is required due to the access control policies configured. Please see [[phab:T251305#7314778|this comment]] for a more detailed explanation of how this pattern arose.
#Tell the deployment server how to set up the kubeconfig files. This is done by modifying the <code>profile::kubernetes::deployment_server::services</code> hiera key (<code>hieradata/common/profile/kubernetes/deployment_server.yaml</code>) as in the example below:<syntaxhighlight lang="yaml">
        - name: mathoid
+    service-foo:
+        usernames:
+            - name: service-foo
+              owner: mwdeploy
+              group: wikidev
+              mode: "0640"
</syntaxhighlight> Please note that the owner/group/mode here refer to the file permissions of your kubeconfig file ("/etc/kubernetes/service-foo-<cluster_name>.config"), determining which users/groups will be able to use this kubeconfig. Typically for normal service users you don't need to define them, as the defaults are correct.
#Ask Service Ops to add the private data for your service. This is done by adding an entry for service-foo under <code>profile::kubernetes::deployment_server_secrets::services</code> in the private repository (<code>role/common/deployment_server.yaml</code>). Secrets will most likely needed for all clusters, including staging.
#Add a Kubernetes namespace. Example commit:
#* '''kubernetes namespace:''' deployment-charts
#At this point, you can safely merge the changes (after '''somebody from Service Ops validates'''). After merging, it is important to run the commands in the next step, so to avoid impacting other people rolling out changes later on.
#Setting up in staging-codfw cluster (and then to the other clusters)
'''On a cumin server''' ({{CuminHosts}})
sudo cumin -b 4 -s 2 kubemaster* 'run-puppet-agent'
'''On deploy1002:'''
sudo run-puppet-agent
sudo -i
cd /srv/deployment-charts/helmfile.d/admin_ng/
helmfile -e staging-codfw -i apply
The command above should show you a diff in namespaces/quotas/etc.. related to your new service. If you don't see a diff, ping somebody from the Service Ops team! Check that everything is ok:
sudo -i
kube_env admin staging-codfw
kubectl describe ns $YOUR-SERVICE-NAME
You should be able to see info about your namespace.
'''Repeat for the staging-eqiad, eqiad and codfw clusters even if you aren't ready to fully deploy your service. Leaving undeployed things will impede further operations by other people.'''
==== Deploy a service to staging ====
At this point you should have a a Chart for your service (TODO: link to docs?), and will need to setup a <code>helmfile.d/services</code> directory in the {{Gitweb|project=operations/deployment-charts}} repository for the deployment. You can copy the structure (helmfile.yaml, values.yaml, values-staging.yaml, etc.) from {{Gitweb|project=operations/deployment-charts|file=helmfile.d/services/_example_}} and customize as needed.
You can proceed to deploy the new service to staging for real. Don't worry for TLS (if needed) since in staging it will be added a default config for your service auto-magically. Things are slightly different for production.
'''On deploy1002:'''
  cd /srv/deployment-charts/helmfile.d/services/service-foo
  helmfile -e staging -i apply
The command above will show a diff related to the new service, make sure  that everything looks fine and then hit Yes to proceed.
==== Testing a service ====
#Now we can test the service in staging. Use the very handy endpoint: <code>http(s)://staging.svc.eqiad.wmnet:$YOUR-SERVICE-PORT</code> to quickly test if everything works as expected.
==== Deploy a service to production ====
#Create certificates for the new service, if it has an HTTPS endpoint (remember that this step for staging is automatically handled for you, but for production it is not).
#[[Kubernetes/Enabling TLS|Enable TLS for Kubernetes deployments]]
#At this point, you need to update the admin config for eqiad and codfw (if you have configs for both of course):
#*On deploy1002: <code>sudo -i; cd /srv/deployment-charts/helmfile.d/admin/codfw/; kube_env admin codfw; ./ -i apply</code>
#*On deploy1002: <code>sudo -i; cd /srv/deployment-charts/helmfile.d/admin/eqiad/; kube_env admin eqiad; ./ -i apply</code>
#Then the final step, namely deploying the new service:
#*On deploy1002: <code>cd /srv/deployment-charts/helmfile.d/services/service-foo; helmfile -e codfw -i apply</code>
#*On deploy1002: <code>cd /srv/deployment-charts/helmfile.d/services/service-foo; helmfile -e eqiad -i apply</code>
The service can now be accessed via the registered port on any of the kubernetes nodes (for manual testing).
If you need the service to be easily accessible from outside of the cluster, you might want to add [[LVS#Add%20a%20new%20load%20balanced%20service|Add a new load balanced service]].

=== Rebooting a worker node ===
=== Rebooting a worker node ===

Revision as of 12:50, 2 May 2022

For information about Kubernetes in the Toolforge environment see Help:Toolforge/Kubernetes.

Kubernetes (often abbreviated k8s) is an open-source system for automating deployment, and management of applications running in containers. This page collects some notes/docs on the Kubernetes setup in the Foundation production environment.


The list of currently maintained clusters in WMF, split by realm and team is at Kubernetes/Clusters


We deploy kubernetes in WMF production using Debian packages where appropriate. There is an upgrade policy in place for defining the timeframe and versions we run at every point in time. It's under Kubernetes/Kubernetes_Infrastructure_upgrade_policy. For more technical information on how we build the Debian packages have a look at Kubernetes/Packages


For how our images are built and maintained have a look at Kubernetes/Images


A service in Kubernetes is an "abstract way to expose an application running on a set of workloads as a network service". That creates an overload of the term, as we also use the term "services" to describe how our various in-house developed applications are exposed to the rest of the infrastructure or the public. It's worthwhile to make sure one is on the same page as the other side when having a conversation around "services". Below there are some links to basic documentation about both concepts to help differentiate between them.


For a quick intro into the debugging actions one can take during a problem in production look at Kubernetes/Helm. There will also be a guide posted under Kubernetes/Kubectl


Create a new cluster

Documentation for creating a new cluster is in Kubernetes/Clusters/New

Add a new service

Documentation on how to deploy a new service can be found at Kubernetes/Add_a_new_service

Rebooting a worker node

The unpolite way

To reboot a worker node, you can just reboot it in our environment. The platform will understand the event and respawn the pods on other nodes. However the system does not automatically rebalance itself currently (pods are not rescheduled on the node after it has been rebooted)

The polite way (recommended)

If you feel like being more polite, use kubectl drain, it will configure the worker node to no longer create new pods and move the existing pods to other workers. Draining the node will take time. Rough numbers on 2019-12-11 are at around 60 seconds.

# kubectl drain --ignore-daemonsets kubernetes1001.eqiad.wmnet
# kubectl describe pods  --all-namespaces | awk  '$1=="Node:" {print $NF}' | sort -u
# kubectl get nodes
NAME                         STATUS                     ROLES     AGE       VERSION
kubernetes1001.eqiad.wmnet   Ready,SchedulingDisabled   <none>    2y352d    v1.12.9
kubernetes1002.eqiad.wmnet   Ready                      <none>    2y352d    v1.12.9
kubernetes1003.eqiad.wmnet   Ready                      <none>    2y352d    v1.12.9
kubernetes1004.eqiad.wmnet   Ready                      <none>    559d      v1.12.9
kubernetes1005.eqiad.wmnet   Ready                      <none>    231d      v1.12.9
kubernetes1006.eqiad.wmnet   Ready                      <none>    231d      v1.12.9

When the node has been rebooted, it can be configured to reaccept pods using kubectl uncordon, e.g.

# kubectl uncordon kubernetes1001.eqiad.wmnet
# kubectl get nodes
NAME                         STATUS    ROLES     AGE       VERSION
kubernetes1001.eqiad.wmnet   Ready     <none>    2y352d    v1.12.9
kubernetes1002.eqiad.wmnet   Ready     <none>    2y352d    v1.12.9
kubernetes1003.eqiad.wmnet   Ready     <none>    2y352d    v1.12.9
kubernetes1004.eqiad.wmnet   Ready     <none>    559d      v1.12.9
kubernetes1005.eqiad.wmnet   Ready     <none>    231d      v1.12.9
kubernetes1006.eqiad.wmnet   Ready     <none>    231d      v1.12.9

The pods are not rebalanced automatically, i.e. the rebooted node is free of pods initially.

Restarting specific components

kube-controller-manager and kube-scheduler are components of the API server. In production multiple ones run and perform via the API an election to determine which one is the master. Restarting both is without grave consequences so it's safe to do. However both are critical components in as such that there are required for the overall cluster to function smoothly. kube-scheduler is crucial for node failovers, pod evictions, etc while kube-controller-manager packs multiple controller components and is critical for responding to pod failures, depools etc.

commands would be

sudo systemctl restart kube-controller-manager
sudo systemctl restart kube-scheduler

Restarting the API server

It's behind LVS in production, it's fine to restart it as long as enough time is given between the restarts across the cluster.

sudo systemctl restart kube-apiserver

If you need to restart all API servers, it might be wise to start with the ones that are not currently leading the cluster (to avoid multiple leader elections). The current leader is stored in the annotation of the kube-scheduler endpoint:

kubectl -n kube-system describe ep kube-scheduler

Switch the active staging cluster (eqiad<->codfw)

We do have one staging cluster per DC, mostly to separate staging of kubernetes and components from staging of the services running on top of it. To provide staging services during work on one of the clusters, we can (manually) switch between the DCs:

Managing pods, jobs and cronjobs

Commands should be run from the deployment servers (at the time of this writing deploy1002).

You need to set the correct context, for example:

kube_env <your service> eqiad

Other choices are codfw, staging.

The management commands is called kubectl. You may find some more inspiration on kubectl commands at Kubernetes/kubectl_Cheat_Sheet

Listing cronjobs, jobs and pods

kubectl get cronjobs -n <namespace>
kubectl get jobs -n <namespace>
kubectl get pods -n <namespace>

Deleting a job

kubectl delete job <job id>

Updating the docker image run by a CronJob

The relationship between the resources is the following:

Cronjob --spawns--> Job(s) --spawns--> Pod(s)

Note: Technically speaking, it's a tight control loop that lives in kube-controller-manager that does the spawning part, but adding that to the above would make this more confusing.

Under normal conditions a docker image version will be updated when a new deploy happens. The cronjob will have the new version. However, already created jobs by the CronJob will not be stopped until they have run to completion.

When the job finishes, the cronjob will create new job(s), which in turn will create new pod(s).

Depending on the correlation between a CronJob scheduling and the job run time there might be a window of time where despite the new deployment, the old job is still running.

Deleting the kubernetes pod created by the job itself will NOT work, i.e. the job will still exist and it will create a new pod (which will still have the old image).

So, if we are dealing with a long running kubernetes Job one can get the same effect by deleting the kubernetes job created by the cronjob.

phab:T280076 is an example where this was needed.

Recreate pods (of deployments, daemonsets, statefulsets, ...)

Pods which are backed by workloads controllers (such as Deployments or Daemonsets) can be easily recreated, without the need to manually delete them, using `kubectl rollout`. This will make sure that the update strategy specified for the set of pods as well as disruption budgets etc. are properly honored.

To restart all pods of a specific Deployment/Daemonset:

kubectl -n NAMESPACE rollout restart [deployment|daemonset|statefulset|...] NAME

You may also restart all Pods of all Deployments/Daemonsets in a specific namespace just by omitting the name. The command will immediately return (e.g. not wait for the process to complete) and the scheduler will do the actual rolling restart in background for you.

In order to restart workload across multiple namespaces, one can use something like:

kubectl get ns -l -o jsonpath='{.items[*]}' | xargs -L1 -d ' ' kubectl rollout restart deployment -n

With or without label filters. The above ensures that for example workload in pre-defined namespaces (like kube-system) does not get restarted.

Running a rolling restart of a Helmfile service

To rolling-restart a service described by a Helmfile, you don't need to use kubectl; instead, run

cd /srv/deployment-charts/helmfile.d/services/${SERVICE?}
helmfile -e ${CLUSTER?} --state-values-set roll_restart=1 sync

See also

Toolforge Info