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Pod Disruption Budget Generation Environment Variable Proposal

Background and Problem Statement

The Strimzi Kafka operator currently lacks the option to disable the creation of Pod Disruption Budgets (PDBs). In certain infrastructures, PDB creations for users are denied, resulting in operational challenges. Providing an option to disable PDB creation in Strimzi would address these constraints.

Proposed Solution

Introduce a new environment variable in Strimzi, similar to the one for Network Policies, that allows global disabling of PDB creation. This proposal suggests the environment variable STRIMZI_POD_DISRUPTION_BUDGET_GENERATION, which by default is true. When set to false, the Strimzi operator will not generate Pod Disruption Budgets.

Rationale

  • Operational Constraints: In environments where the creation of Pod Disruption Budgets (PDBs) is not permitted, users face significant challenges in deploying Strimzi effectively. This limitation can hinder the adoption and utility of Strimzi in such environments.

  • Configuration Flexibility: Users require the flexibility to configure their Strimzi deployments in accordance with their specific operational policies and constraints. A rigid approach that mandates the creation of PDBs may not be compatible with all operational environments.

  • Consistency with Existing Features: Implementing this feature as an environment variable aligns with the existing approach used for Network Policy Generation in Strimzi. This consistency simplifies the understanding and adoption of the feature by existing users.

  • Simplicity and Ease of Use: Offering a global setting to disable PDB generation avoids the complexity and repetitive configuration that would be required if this setting was to be managed at the individual custom resource level.

Current Implementation

The Strimzi operator automatically creates PDBs to ensure high availability and minimize disruptions. However, this feature does not accommodate environments where PDB creation is restricted.

Proposal Details

  1. Environment Variable Introduction: Implement STRIMZI_POD_DISRUPTION_BUDGET_GENERATION with a default value of true.
  2. Disabling PDB Generation: When set to false, the operator will skip PDB operations for all Strimzi components. It will not create, modify or delete any PDB.
  3. Documentation and Guidance: Update Strimzi documentation to include instructions and implications of disabling PDB generation.
  4. Scope: This change affects only the Pod Disruption Budget aspect and does not alter any other functionalities of the Strimzi operator.

Affected Projects

This proposal pertains solely to the Strimzi Kafka Operator.

Compatibility

  • Default Behavior: By retaining true as the default value, existing deployments remain unaffected.
  • Backward Compatibility: This feature is an addition and does not alter existing functionalities.

Rejected Alternatives

  1. CRD-based Option for PDB Disabling: Initially considered, this was rejected for increasing complexity and requiring repetitive configuration.
  2. Global Disabling via Command-Line Flag in Strimzi Image Entrypoint: Initially considered as an alternative, using a flag in the entrypoint command of the Strimzi image was ultimately deemed less flexible and consistent compared to an environment variable. This approach, while feasible, does not align as seamlessly with the configuration practices commonly used in Strimzi deployments.

Conclusion

Introducing an environment variable to globally control PDB generation in Strimzi provides the necessary flexibility for users operating in environments with strict PDB creation policies, while maintaining the ease of use and consistency with existing Strimzi features.