Version: 2.4.2

Running and Managing Workloads

Running user workloads#

Once your cluster is up and running it's time to put it work!

Managing workloads with GitOps#

WKP encourages using GitOps to manage your workloads. We can specify the state of the cluster including all our user workloads in the config git repository. The WKP Flux Cluster Component will ensure that the git repository and the cluster then stay in sync. This gives us a number of benefits including

An audit trail of who deployed or updated a workload and why
Deployment rollbacks via git revert

Additionally WKP clusters support all the traditional ways of creating and deploying workloads through kubectl and the api-server directly. Check out the Kubernetes docs to familiarize yourself with these tools.

Adding a workload#

By default the ./cluster/manifests path within the config repository is reserved for user manifests. Any .yaml Kubernetes manifest you add within this path will be deployed to the cluster automatically.

Example: Adding nginx#

Lets create a new file: ./cluster/manifests/nginx.yaml and set the contents:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  selector:
    matchLabels:
      app: nginx
  replicas: 1
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
        - name: nginx
          image: nginx:1.14.2
          ports:
            - containerPort: 80

Save the file, then we'll commit and push it to the repository host

git add ./cluster/manifests/nginx.yaml
git commit -m "Deploying nginx to the cluster"
git push origin master

Checking a workload is deployed#

Once we have pushed we can check the workload is deployed in the cluster like with kubectl:

kubectl get pods

NAME                                READY   STATUS    RESTARTS   AGE
nginx-deployment-574b87c764-mth9r   1/1     Running   0          16s

There is a new pod running!

View the new workload in Weave Scope#

We can use the Weave Scope Cluster Component to view all the workloads running on the cluster. First open the WKP ui

wk ui

Then when the browser opens click the "Open Scope" button in the Cluster Components list. You can use Scope to explore whats running on your cluster.

Nginx in Scope

View the UI#

We can view the Web UI of a pod by forwarding the http ports it listens on

kubectl port-forward deployment/nginx-deployment 8080:80

opening http://localhost:8080 in your browser will show the default nginx server response

Check logs#

We can check the logs of our new pod via kubectl

kubectl logs deployment/nginx-deployment

127.0.0.1 - - [05/Jun/2020:10:15:26 +0000] "GET / HTTP/1.1" 200 612 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_4) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/13.1 Safari/605.1.15" "-"
127.0.0.1 - - [05/Jun/2020:10:15:26 +0000] "GET /favicon.ico HTTP/1.1" 404 169 "http://localhost:8080/" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_4) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/13.1 Safari/605.1.15" "-"
2020/06/05 10:15:26 [error] 6#6: *1 open() "/usr/share/nginx/html/favicon.ico" failed (2: No such file or directory), client: 127.0.0.1, server: localhost, request: "GET /favicon.ico HTTP/1.1", host: "localhost:8080", referrer: "http://localhost:8080/"

displaying the requests we just made.

Updating a workload#

A common operation is upgrading a version of a workload when there is a new release. To do that we can edit the .yaml file and change the docker image to the desired tag:

vim cluster/manifests/nginx.yaml
git diff

diff --git a/cluster/manifests/nginx.yaml b/cluster/manifests/nginx.yaml
index 91f07bf..198b404 100644
--- a/cluster/manifests/nginx.yaml
+++ b/cluster/manifests/nginx.yaml
@@ -14,7 +14,7 @@ spec:
     spec:
       containers:
       - name: nginx
-        image: nginx:1.14.2
+        image: nginx:1.16.1
         ports:
         - containerPort: 80

Then once again we can commit and push to update the cluster:

git add ./cluster/manifests/nginx.yaml
git commit -m "Update nginx to 1.16.1"
git push origin master

Debugging#

If a change to the git repository does not seem to be reflected in the cluster we can take some steps to investigate

Verify the `flux-sync` git tag#

When flux applies a commit it will update a git tag on the repository. If you don't have access to the flux pod's logs this is a handy way of checking what was last sync'd:

$ git pull
remote: Counting objects: 1, done.
remote: Total 1 (delta 0), reused 0 (delta 0)
Unpacking objects: 100% (1/1), 148 bytes | 148.00 KiB/s, done.
From gitlab.dev.wkp.weave.works:foot/simon-gcp-59
 * [new tag]         flux-sync  -> flux-sync
Already up to date.

We can inspect the tag and see when flux last updated it and which commit was last applied.

git show flux-sync -q
tag flux-sync
Tagger: Weave Flux <support@weave.works>
Date:   Fri Jun 5 10:12:29 2020 +0000

Sync pointer

commit d81af6571f525d924e896a5fbcd0706abd09a7ee (HEAD -> master, tag: flux-sync, origin/master)
Author: WKP Support <support@weave.works>
Date:   Fri Jun 5 12:12:17 2020 +0200

    Deploying nginx to the cluster

Flux is configured by default to poll and apply the git repository every 10s. If after waiting this long the tag has not updated flux might be having trouble syncing the repository. To learn more we need to check its logs.

Check the flux logs for errors#

We can inspect the flux logs with:

kubectl logs -n wkp-flux deployment/flux

Flux will report any errors raised while it was applying the yaml manifests. This can include things like:

Unable to read the git repository if there are connectivity issues.
Syntax errors in the .yaml manifest files
Kubernetes validation errors if the manifest files are badly formed.

Correct any errors in your yaml files and then try commiting and pushing your changes again.

Remove a workload#

Removing a workload is again a simple operation on the config repository:

git rm ./cluster/manifests/nginx.yaml
git commit -m "Removing nginx for now"
git push origin master

Flux will sync and remove the workload from the cluster.