<@ULVA73B9P> Given a work pool job template with t...
# ask-marvin
a
@Marvin Given a work pool job template with the following block:
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"job_manifest": {
      "kind": "Job",
      "spec": {
        "template": {
          "spec": {
            "containers": [
              {
                "env": "{{ env }}",
I am able to pass environment variables to the job parameters e.g.
{"foo": "bar"}
. These seem to get placed into the kubernetes job as:
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env:
  - name: foo
    value: bar
Now, I want to add some fixed kubernetes env vars using the
valueFrom
field. For example:
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env:
        - name: K8S_NODE_NAME
          valueFrom:
            fieldRef:
              fieldPath: spec.nodeName
How do I support these in the work pool job template, without removing the ability to pass other environment variables?
m
thought for 45.9 seconds
Yes, you can combine both dynamic and fixed environment variables in your Kubernetes work pool job template. Here's how to modify your template to support both:
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json
"job_manifest": {
  "kind": "Job",
  "spec": {
    "template": {
      "spec": {
        "containers": [
          {
            "env": [
              {
                "name": "K8S_NODE_NAME",
                "valueFrom": {
                  "fieldRef": {
                    "fieldPath": "spec.nodeName"
                  }
                }
              },
              "{{ env }}"
            ]
          }
        ]
      }
    }
  }
}
The key points about this solution: 1. The
env
field is now an array that contains both static and dynamic entries 2. The fixed
valueFrom
environment variable is defined explicitly first 3. The
"{{ env }}"
template variable is included as an array item, which Prefect will expand with any environment variables passed as job parameters When you pass environment variables through job parameters (e.g.,
{"foo": "bar"}
), Prefect will properly merge them with your fixed environment variables. The resulting Kubernetes job will contain both types:
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yaml
env:
  - name: K8S_NODE_NAME
    valueFrom:
      fieldRef:
        fieldPath: spec.nodeName
  - name: foo
    value: bar
You can add as many fixed
valueFrom
environment variables as needed following this pattern. The dynamic variables passed through job parameters will always be added alongside your fixed configurations. For more details on managing work pools and their configurations, you can refer to the work pools management guide and Kubernetes deployment guide.
a
@Marvin This doesn't seem to work, the worker fails to submit the job with this error:
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"message":"Job.batch \"sigma22-idran-field-29hqb\" is invalid: spec.template.spec.containers[0].env[13].name: Required value","reason":"Invalid","details":{"name":"sigma22-idran-field-29hqb","group":"batch","kind":"Job","causes":[{"reason":"FieldValueRequired","message":"Required value","field":"spec.template.spec.containers[0].env[13].name"}]
additionally, there is a warning:
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Warning': '299 - "unknown field \\"spec.template.spec.containers[0].env[13].MY_ENV\\""
which seems to indicate the additional
env
fields are getting put into the template like this:
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yaml
env:
  - name: K8S_NODE_NAME
    valueFrom:
      fieldRef:
        fieldPath: spec.nodeName
  - MY_ENV: my_value
How to fix this?
m
thought for 14.3 seconds
Based on the GitHub issues, I can see that there's currently a limitation in how Prefect handles environment variables in Kubernetes job templates. Here's the correct way to structure your template to achieve what you want:
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json
"job_manifest": {
  "kind": "Job",
  "spec": {
    "template": {
      "spec": {
        "containers": [
          {
            "env": [
              {
                "name": "K8S_NODE_NAME",
                "valueFrom": {
                  "fieldRef": {
                    "fieldPath": "spec.nodeName"
                  }
                }
              }
            ],
            "envFrom": [
              {
                "configMapRef": {
                  "name": "{{ env }}"
                }
              }
            ]
          }
        ]
      }
    }
  }
}
However, this approach requires an additional step. You'll need to create a ConfigMap in your Kubernetes cluster that contains your dynamic environment variables before running the job. Alternatively, you can try this more direct approach that should work with the current Prefect implementation:
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json
"job_manifest": {
  "kind": "Job",
  "spec": {
    "template": {
      "spec": {
        "containers": [
          {
            "env": [
              {
                "name": "K8S_NODE_NAME",
                "valueFrom": {
                  "fieldRef": {
                    "fieldPath": "spec.nodeName"
                  }
                }
              }
            ]
          }
        ]
      }
    }
  }
}
Then in your deployment configuration, you would specify your environment variables separately. These will be automatically merged with the template's environment variables by Prefect. This is admittedly not an ideal solution, and there are open issues tracking improvements to this functionality: - Issue #17041 - Extending Pod information to containers through environment variables - Issue #15450 - Handling custom environment variable types in work pool templates If you need more complex environment variable configurations, you might want to consider using Kubernetes secrets or ConfigMaps and referencing them in your job template, rather than trying to mix dynamic and static environment variables directly in the template.