kubevela/docs/en/end-user/explore.md

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Explore Applications

We will introduce how to explore application related resources in this section.

List Application

$ kubectl get application
NAME        COMPONENT   TYPE         PHASE     HEALTHY   STATUS   AGE
app-basic   app-basic   webservice   running   true               12d
website     frontend    webservice   running   true               4m54s

You can also use the short name kubectl get app.

View Application Details

$ kubectl get app website -o yaml
apiVersion: core.oam.dev/v1beta1
kind: Application
metadata:
  generation: 1
  name: website
  namespace: default
spec:
  components:
  - name: frontend
    properties:
      image: nginx
    traits:
    - properties:
        cpuPercent: 60
        max: 10
        min: 1
      type: cpuscaler
    - properties:
        image: fluentd
        name: sidecar-test
      type: sidecar
    type: webservice
  - name: backend
    properties:
      cmd:
      - sleep
      - "1000"
      image: busybox
    type: worker
status:
  ...
  latestRevision:
    name: website-v1
    revision: 1
    revisionHash: e9e062e2cddfe5fb
  services:
  - healthy: true
    name: frontend
    traits:
    - healthy: true
      type: cpuscaler
    - healthy: true
      type: sidecar
  - healthy: true
    name: backend
  status: running

Here are some highlight information that you need to know:

1. status.latestRevision declares current revision of this application.
2. status.services declares the component created by this application and the healthy state.
3. status.status declares the global state of this application.

List Application Revisions

When we update an application, if there's any difference on spec, KubeVela will create a new revision.

$ kubectl get apprev -l app.oam.dev/name=website
NAME           AGE
website-v1     35m

Explore Components

You can explore what kinds of component definitions supported in your system.

kubectl get comp -n vela-system
NAME              WORKLOAD-KIND   DESCRIPTION                        
task              Job             Describes jobs that run code or a script to completion.                                                                                          
webservice        Deployment      Describes long-running, scalable, containerized services that have a stable network endpoint to receive external network traffic from customers. 
worker            Deployment      Describes long-running, scalable, containerized services that running at backend. They do NOT have network endpoint to receive external network traffic.

The component definition objects are namespace isolated align with application, while the vela-system is a common system namespace of KubeVela, definitions laid here can be used by every application.

You can use vela kubectl plugin to view the detail usage of specific component definition.

$ kubectl vela show webservice
# Properties
+------------------+----------------------------------------------------------------------------------+-----------------------+----------+---------+
|       NAME       |                                   DESCRIPTION                                    |         TYPE          | REQUIRED | DEFAULT |
+------------------+----------------------------------------------------------------------------------+-----------------------+----------+---------+
| cmd              | Commands to run in the container                                                 | []string              | false    |         |
| env              | Define arguments by using environment variables                                  | [[]env](#env)         | false    |         |
| addRevisionLabel |                                                                                  | bool                  | true     | false   |
| image            | Which image would you like to use for your service                               | string                | true     |         |
| port             | Which port do you want customer traffic sent to                                  | int                   | true     |      80 |
| cpu              | Number of CPU units for the service, like `0.5` (0.5 CPU core), `1` (1 CPU core) | string                | false    |         |
| volumes          | Declare volumes and volumeMounts                                                 | [[]volumes](#volumes) | false    |         |
+------------------+----------------------------------------------------------------------------------+-----------------------+----------+---------+


##### volumes
+-----------+---------------------------------------------------------------------+--------+----------+---------+
|   NAME    |                             DESCRIPTION                             |  TYPE  | REQUIRED | DEFAULT |
+-----------+---------------------------------------------------------------------+--------+----------+---------+
| name      |                                                                     | string | true     |         |
| mountPath |                                                                     | string | true     |         |
| type      | Specify volume type, options: "pvc","configMap","secret","emptyDir" | string | true     |         |
+-----------+---------------------------------------------------------------------+--------+----------+---------+


## env
+-----------+-----------------------------------------------------------+-------------------------+----------+---------+
|   NAME    |                        DESCRIPTION                        |          TYPE           | REQUIRED | DEFAULT |
+-----------+-----------------------------------------------------------+-------------------------+----------+---------+
| name      | Environment variable name                                 | string                  | true     |         |
| value     | The value of the environment variable                     | string                  | false    |         |
| valueFrom | Specifies a source the value of this var should come from | [valueFrom](#valueFrom) | false    |         |
+-----------+-----------------------------------------------------------+-------------------------+----------+---------+


### valueFrom
+--------------+--------------------------------------------------+-------------------------------+----------+---------+
|     NAME     |                   DESCRIPTION                    |             TYPE              | REQUIRED | DEFAULT |
+--------------+--------------------------------------------------+-------------------------------+----------+---------+
| secretKeyRef | Selects a key of a secret in the pod's namespace | [secretKeyRef](#secretKeyRef) | true     |         |
+--------------+--------------------------------------------------+-------------------------------+----------+---------+


#### secretKeyRef
+------+------------------------------------------------------------------+--------+----------+---------+
| NAME |                           DESCRIPTION                            |  TYPE  | REQUIRED | DEFAULT |
+------+------------------------------------------------------------------+--------+----------+---------+
| name | The name of the secret in the pod's namespace to select from     | string | true     |         |
| key  | The key of the secret to select from. Must be a valid secret key | string | true     |         |
+------+------------------------------------------------------------------+--------+----------+---------+

Explore Traits

You can explore what kinds of trait definitions supported in your system.

$ kubectl get trait -n vela-system
NAME                                       APPLIES-TO            DESCRIPTION                                     
cpuscaler                                  [webservice worker]   configure k8s HPA with CPU metrics for Deployment
ingress                                    [webservice worker]   Configures K8s ingress and service to enable web traffic for your service. Please use route trait in cap center for advanced usage.
scaler                                     [webservice worker]   Configures replicas for your service.
sidecar                                    [webservice worker]   inject a sidecar container into your app

The trait definition objects are namespace isolated align with application, while the vela-system is a common system namespace of KubeVela, definitions laid here can be used by every application.

You can use kubectl vela show to see the usage of specific trait definition.

$ kubectl vela show sidecar
# Properties
+---------+-----------------------------------------+----------+----------+---------+
|  NAME   |               DESCRIPTION               |   TYPE   | REQUIRED | DEFAULT |
+---------+-----------------------------------------+----------+----------+---------+
| name    | Specify the name of sidecar container   | string   | true     |         |
| image   | Specify the image of sidecar container  | string   | true     |         |
| command | Specify the commands run in the sidecar | []string | false    |         |
+---------+-----------------------------------------+----------+----------+---------+