Version: v1.1

Attaching Sidecar

The sidecar trait allows you to attach a sidecar container to the component.

Specification

  1. kubectl vela show sidecar
  1. # Properties
  2. +---------+-----------------------------------------+-----------------------+----------+---------+
  3. |  NAME   |               DESCRIPTION               |         TYPE          | REQUIRED | DEFAULT |
  4. +---------+-----------------------------------------+-----------------------+----------+---------+
  5. | name    | Specify the name of sidecar container   | string                | true     |         |
  6. | cmd     | Specify the commands run in the sidecar | []string              | false    |         |
  7. | image   | Specify the image of sidecar container  | string                | true     |         |
  8. | volumes | Specify the shared volume path          | [[]volumes](#volumes) | false    |         |
  9. +---------+-----------------------------------------+-----------------------+----------+---------+
  14. ## volumes
  15. +-----------+-------------+--------+----------+---------+
  16. |   NAME    | DESCRIPTION |  TYPE  | REQUIRED | DEFAULT |
  17. +-----------+-------------+--------+----------+---------+
  18. | name      |             | string | true     |         |
  19. | path      |             | string | true     |         |
  20. +-----------+-------------+--------+----------+---------+

How to use

In this Application, component log-gen-worker and sidecar share the data volume that saves the logs. The sidebar will re-output the log to stdout.

  1. # app.yaml
  2. apiVersion: core.oam.dev/v1beta1
  3. kind: Application
  4. metadata:
  5.   name: vela-app-with-sidecar
  6. spec:
  7.   components:
  8.     - name: log-gen-worker
  9.       type: worker
  10.       properties:
  11.         image: busybox
  12.         cmd:
  13.           - /bin/sh
  14.           - -c
  15.           - >
  16.             i=0;
  17.             while true;
  18.             do
  19.               echo "$i: $(date)" >> /var/log/date.log;
  20.               i=$((i+1));
  21.               sleep 1;
  22.             done
  23.         volumes:
  24.           - name: varlog
  25.             mountPath: /var/log
  26.             type: emptyDir
  27.       traits:
  28.         - type: sidecar
  29.           properties:
  30.             name: count-log
  31.             image: busybox
  32.             cmd: [ /bin/sh, -c, 'tail -n+1 -f /var/log/date.log']
  33.             volumes:
  34.               - name: varlog
  35.                 path: /var/log

Deploy this Application.

  1. kubectl apply -f app.yaml

On runtime cluster, check the name of running pod.

  1. kubectl get pod
  1. NAME                              READY   STATUS    RESTARTS   AGE
  2. log-gen-worker-76945f458b-k7n9k   2/2     Running   0          90s

And check the logging output of sidecar.

  1. kubectl logs -f log-gen-worker-76945f458b-k7n9k count-log
  1. 0: Fri Apr 16 11:08:45 UTC 2021
  2. 1: Fri Apr 16 11:08:46 UTC 2021
  3. 2: Fri Apr 16 11:08:47 UTC 2021
  4. 3: Fri Apr 16 11:08:48 UTC 2021
  5. 4: Fri Apr 16 11:08:49 UTC 2021
  6. 5: Fri Apr 16 11:08:50 UTC 2021
  7. 6: Fri Apr 16 11:08:51 UTC 2021
  8. 7: Fri Apr 16 11:08:52 UTC 2021
  9. 8: Fri Apr 16 11:08:53 UTC 2021
  10. 9: Fri Apr 16 11:08:54 UTC 2021