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Renovate Configuration: Centralized vs. Per-Repository

Centralized Configuration
Per-Repository Configuration
Trade-offs: Centralized vs. Per-Repository Configuration
When to Use Centralized Configuration
When to Use Per-Repository Configuration
Conclusion

This document compares two approaches for configuring Renovate: centralized configuration and per-repository configuration. Both approaches have distinct advantages and drawbacks, and the best choice depends on your team’s needs and the structure of your repositories.

Centralized Configuration

Centralized configuration allows you to define Renovate settings in one place, which applies across multiple repositories. This method is ideal for teams that need consistent behavior across repositories, reducing the need for repeated configuration and simplifying maintenance.

Example: Centralized Configuration

{
    "packageRules": [
        {
            "matchDatasources": [
                "terraform-provider"
            ],
            "registryUrls": [
                "https://registry.opentofu.org"
            ],
            "postUpgradeTasks": {
                "commands": [
                    "./scripts/update-terraform-docs.sh"
                ],
                "fileFilters": [
                    "modules/**/*"
                ],
                "executionMode": "update"
            }
        }
    ]
}

Benefits of Centralized Configuration

Single Source of Truth: A single configuration file governs Renovate’s behavior across all repositories.
Simplified Maintenance: Changes to scripts, file filters, or other settings need to be made only once.
Consistency: Ensures uniform behavior across repositories, particularly when shared scripts or tasks are involved.
Scalability: Ideal for organizations managing a large number of repositories with similar requirements.

Limitations of Centralized Configuration

Limited Flexibility: All repositories must adhere to the same configuration, which makes it difficult to apply repository-specific tasks or structures.
Assumes Similar Structure: The configuration assumes that all repositories follow a similar structure (e.g., modules/**/*), which might not always be the case.

Per-Repository Configuration

Per-repository configuration allows each repository to have its own renovate.json file with custom settings. This approach is beneficial when individual repositories require unique tasks, scripts, or behaviors that can’t be generalized.

Example: Per-Repository Configuration

{
    "packageRules": [
        {
            "matchDatasources": [
                "terraform-provider"
            ],
            "registryUrls": [
                "https://registry.opentofu.org"
            ],
            "postUpgradeTasks": {
                "commands": [
                    "./scripts/update-terraform-docs.sh"
                ],
                "fileFilters": [
                    "modules/**/*"
                ],
                "executionMode": "update"
            }
        }
    ]
}

Benefits of Per-Repository Configuration

Complete Flexibility: Allows repository-specific settings, such as custom post-upgrade tasks or different file filters.
Tailored for Unique Repositories: Ideal for repositories that require distinct workflows, dependencies, or tasks that differ from the rest.

Limitations of Per-Repository Configuration

Duplication: Similar configuration settings may need to be repeated across multiple repositories, leading to inconsistency or errors if updates are missed.
Higher Maintenance Overhead: Each repository’s configuration file must be maintained separately, which can become cumbersome with a large number of repositories.
Inconsistent Behavior: If different teams handle configurations independently, this can lead to inconsistent behavior across repositories.

Trade-offs: Centralized vs. Per-Repository Configuration

Aspect	Centralized Configuration	Per-Repository Configuration
Maintenance	Easier to maintain due to a single configuration.	Requires maintaining separate files for each repository.
Flexibility	Less flexible, as all repositories share the same behavior.	Highly flexible, allowing for tailored behavior per repository.
Consistency	Ensures consistent behavior across repositories.	Potential for inconsistencies across repositories.
Scalability	Scales well for repositories with similar requirements.	More difficult to scale due to the need for individual configurations.

When to Use Centralized Configuration

When your repositories have a consistent structure and require the same Renovate behavior across all of them.
When you want to reduce redundancy and maintain a single configuration file for easier updates.
If your team prefers simplicity and a unified approach.

When to Use Per-Repository Configuration

When different repositories require customized settings, workflows, or post-upgrade tasks.
When you need greater flexibility to handle repositories with varying structures, dependencies, or requirements.
If your repositories have a lot of unique tasks that cannot be generalized.

Conclusion

Centralized Configuration is ideal for teams that prioritize consistency and ease of maintenance across a large set of repositories with similar needs.
Per-Repository Configuration is essential for teams that require customization and flexibility in handling specific repository tasks but comes with higher maintenance and potential inconsistencies.

Carefully consider the structure of your repositories and your team’s workflows to decide which configuration approach aligns best with your needs.

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