Volumes¶
The following example dynamically creates a volume and then uses the volume in a two step workflow.
apiVersion: argoproj.io/v1alpha1
kind: Workflow
metadata:
generateName: volumes-pvc-
spec:
entrypoint: volumes-pvc-example
volumeClaimTemplates: # define volume, same syntax as k8s Pod spec
- metadata:
name: workdir # name of volume claim
spec:
accessModes: [ "ReadWriteOnce" ]
resources:
requests:
storage: 1Gi # Gi => 1024 * 1024 * 1024
templates:
- name: volumes-pvc-example
steps:
- - name: generate
template: hello-world-to-file
- - name: print
template: print-message-from-file
- name: hello-world-to-file
container:
image: busybox
command: [sh, -c]
args: ["echo generating message in volume; echo hello world | tee /mnt/vol/hello_world.txt"]
# Mount workdir volume at /mnt/vol before invoking the container
volumeMounts: # same syntax as k8s Pod spec
- name: workdir
mountPath: /mnt/vol
- name: print-message-from-file
container:
image: alpine:latest
command: [sh, -c]
args: ["echo getting message from volume; find /mnt/vol; cat /mnt/vol/hello_world.txt"]
# Mount workdir volume at /mnt/vol before invoking the container
volumeMounts: # same syntax as k8s Pod spec
- name: workdir
mountPath: /mnt/vol
Volumes are a very useful way to move large amounts of data from one step in a workflow to another. Depending on the system, some volumes may be accessible concurrently from multiple steps.
In some cases, you want to access an already existing volume rather than creating/destroying one dynamically.
# Define Kubernetes PVC
kind: PersistentVolumeClaim
apiVersion: v1
metadata:
name: my-existing-volume
spec:
accessModes: [ "ReadWriteOnce" ]
resources:
requests:
storage: 1Gi
---
apiVersion: argoproj.io/v1alpha1
kind: Workflow
metadata:
generateName: volumes-existing-
spec:
entrypoint: volumes-existing-example
volumes:
# Pass my-existing-volume as an argument to the volumes-existing-example template
# Same syntax as k8s Pod spec
- name: workdir
persistentVolumeClaim:
claimName: my-existing-volume
templates:
- name: volumes-existing-example
steps:
- - name: generate
template: hello-world-to-file
- - name: print
template: print-message-from-file
- name: hello-world-to-file
container:
image: busybox
command: [sh, -c]
args: ["echo generating message in volume; echo hello world | tee /mnt/vol/hello_world.txt"]
volumeMounts:
- name: workdir
mountPath: /mnt/vol
- name: print-message-from-file
container:
image: alpine:latest
command: [sh, -c]
args: ["echo getting message from volume; find /mnt/vol; cat /mnt/vol/hello_world.txt"]
volumeMounts:
- name: workdir
mountPath: /mnt/vol
It's also possible to declare existing volumes at the template level, instead of the workflow level.
Workflows can generate volumes using a resource
step.
apiVersion: argoproj.io/v1alpha1
kind: Workflow
metadata:
generateName: template-level-volume-
spec:
entrypoint: generate-and-use-volume
templates:
- name: generate-and-use-volume
steps:
- - name: generate-volume
template: generate-volume
arguments:
parameters:
- name: pvc-size
# In a real-world example, this could be generated by a previous workflow step.
value: '1Gi'
- - name: generate
template: hello-world-to-file
arguments:
parameters:
- name: pvc-name
value: '{{steps.generate-volume.outputs.parameters.pvc-name}}'
- - name: print
template: print-message-from-file
arguments:
parameters:
- name: pvc-name
value: '{{steps.generate-volume.outputs.parameters.pvc-name}}'
- name: generate-volume
inputs:
parameters:
- name: pvc-size
resource:
action: create
setOwnerReference: true
manifest: |
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
generateName: pvc-example-
spec:
accessModes: ['ReadWriteOnce', 'ReadOnlyMany']
resources:
requests:
storage: '{{inputs.parameters.pvc-size}}'
outputs:
parameters:
- name: pvc-name
valueFrom:
jsonPath: '{.metadata.name}'
- name: hello-world-to-file
inputs:
parameters:
- name: pvc-name
volumes:
- name: workdir
persistentVolumeClaim:
claimName: '{{inputs.parameters.pvc-name}}'
container:
image: busybox
command: [sh, -c]
args: ["echo generating message in volume; echo hello world | tee /mnt/vol/hello_world.txt"]
volumeMounts:
- name: workdir
mountPath: /mnt/vol
- name: print-message-from-file
inputs:
parameters:
- name: pvc-name
volumes:
- name: workdir
persistentVolumeClaim:
claimName: '{{inputs.parameters.pvc-name}}'
container:
image: alpine:latest
command: [sh, -c]
args: ["echo getting message from volume; find /mnt/vol; cat /mnt/vol/hello_world.txt"]
volumeMounts:
- name: workdir
mountPath: /mnt/vol