This repository contains the official Prefect Helm charts for installing and configuring Prefect on Kubernetes. These charts support multiple use cases of Prefect on Kubernetes depending on the values provided and chart selected including:
Workers are lightweight polling services that retrieve scheduled runs from a work pool and execute them.
Workers are similar to agents, but offer greater control over infrastructure configuration and the ability to route work to specific types of execution environments.
Workers each have a type corresponding to the execution environment to which they will submit flow runs. Workers are only able to join work pools that match their type. As a result, when deployments are assigned to a work pool, you know in which execution environment scheduled flow runs for that deployment will run.
Agents are part of the block-based deployment model. Work Pools and Workers simplify the specification of a flow's infrastructure and runtime environment. If you have existing agents, you can upgrade from agents to workers to significantly enhance the experience of deploying flows.
Agent processes are lightweight polling services that get scheduled work from a work pool and deploy the corresponding flow runs.
Agents poll for work every 15 seconds by default. This interval is configurable in your profile settings with the PREFECT_AGENT_QUERY_INTERVAL setting.
It is possible for multiple agent processes to be started for a single work pool. Each agent process sends a unique ID to the server to help disambiguate themselves and let users know how many agents are active.
Prefect server is a self-hosted open source backend that makes it easy to observe and orchestrate your Prefect flows. It is an alternative to using the hosted Prefect Cloud platform. Prefect Cloud provides additional features including automations and user management.
The Prometheus Prefect Exporter is a tool to pull relevant Prefect metrics from a hosted Prefect Server instance
Helm must be installed to use the charts. Please refer to Helm's documentation to get started.
helm repo add prefect https://prefecthq.github.io/prefect-helm
helm search repo prefect
helm install my-release prefect/prefect-<chart>Charts are automatically versioned and released together. The appVersion and prefectTag version are pinned at package time to the current release of Prefect 2.
The charts are hosted in a Helm repository deployed to the web courtesy of GitHub Pages.
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Add the Prefect Helm repository to Helm and list available charts and versions:
helm repo add prefect https://prefecthq.github.io/prefect-helm helm repo update helm search repo prefect
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Install the Helm chart
Each chart will require some specific configuration values to be provided, see the individual chart README's for more information on configuring and installing the chart.
If chart installation fails, run the same command with
--debugto see additional diagnostic information.Refer to the Helm
installdocumentation for all options.
Development versions of the Helm chart will always be available directly from this Github repository.
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Clone repository
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Change to this directory
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Download the chart dependencies
helm dependency update
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Install the chart
helm install . --generate-name
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Look up the name of the last release
helm list
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Run the upgrade
# Choose a version to upgrade to or omit the flag to use the latest version helm upgrade prefect-server prefect/prefect-server --version 2023.09.07For development versions, make sure your cloned repository is updated (
git pull) and reference the local charthelm upgrade prefect-server . -
Upgrades can also be used enable features or change options
helm upgrade prefect-server prefect/prefect-server --set newValue=true
- Updates will only update infrastructure that is modified.
- You will need to continue to set any values that you set during the original install (e.g.
--set namespaceOverride=prefector--values path/to/values.yaml). - If you are using the postgresql subchart with an autogenerated password, it will complain that you have not provided that password for the upgrade. Export the password as the error asks then set it within the subchart using:
helm upgrade ... --set postgresql.postgresqlPassword=$POSTGRESQL_PASSWORD
See comments in values.yaml.
By default, the agent, worker, and server run as an unprivileged user with a read-only root filesystem. You can customize the security context settings for both the agent and server in the values.yaml file for your use case.
If you need to install system packages or configure other settings at runtime, you can configure a writable filesystem and run as root by configuring the pod and container security context accordingly:
podSecurityContext:
runAsUser: 0
runAsNonRoot: false
fsGroup: 0
containerSecurityContext:
runAsUser: 0
# this must be false, since we are running as root
runAsNonRoot: false
# make the filesystem writable
readOnlyRootFilesystem: false
# this must be false, since we are running as root
allowPrivilegeEscalation: falseIf you are running in OpenShift, the default restricted security context constraint will prevent customization of the user. In this case, explicitly configure the runAsUser settings to null to use OpenShift-assigned settings:
podSecurityContext:
runAsUser: null
fsGroup: null
containerSecurityContext:
runAsUser: nullThe other default settings, such as a read-only root filesystem, are suitable for an OpenShift environment.
If you are running flows on your agent’s pod (i.e. with Process infrastructure), and using the Dask task runner to create Dask Kubernetes clusters, you will need to grant the following permissions within values.yaml.
role:
extraPermissions:
- apiGroups: [""]
resources: ["pods", "services"]
verbs: ["get", "list", "watch", "create", "update", "patch", "delete"]
- apiGroups: ["policy"]
resources: ["poddisruptionbudgets"]
verbs: ["get", "list", "watch", "create", "update", "patch", "delete"]Prefect follows the upstream Kubernetes support policy, meaning that we test against the three most recent minor version releases of Kubernetes. The charts may be compatible with older releases of Kubernetes, however, we do not test against those versions and may choose to reject issues or patches to add support.
If you are using the subchart deployed database with persistence enabled, it is likely the password for the user has persisted between deployments in the PVC for the database but the secret has been regenerated by the Helm chart and does not match. Deploy and set the 'postgresql.auth.existingSecret' option or set a constant password at postgresql.auth.password.
Contributions to the Prefect Helm Charts are always welcome! We welcome your help - whether it's adding new functionality, tweaking documentation, or anything in between. In order to successfully contribute, you'll need to fork this repository and commit changes to your local prefect-helm repo. You can then open a PR against this upstream repo that the team will review!
Please make sure that your changes have been linted & the chart documentation has been updated. The easiest way to accomplish this is by installing pre-commit.
Make sure that any new functionality is well tested! You can do this by installing the chart locally, see above for how to do this.
A helpful PR explains WHAT changed and WHY the change is important. Please take time to make your PR descriptions as helpful as possible. If you are opening a PR from a forked repository - please follow these docs to allow prefect-helm maintainers to push commits to your local branch.