Caching issue causes Hephaestus to be out of date

[FelixTJDietrich]

Describe the bug

Sometimes when visiting Hephaestus it is still showing an old version of the code i.e. 5.0.0 even though a new version has already been deployed, i.e. 6.1.0.

This caching potentially also accounts for the query parameters, e.g. hephaestus.aet.cit.tum.de with and without query parameters had different versions.

To Reproduce
Steps to reproduce the behavior:

1. Go to Hephaestus
2. Check the version number
3. Depoy a different version
4. Check the version number

Without clearing the cache it remains the old version number?

Expected behavior

The newest version of Hephaestus should be shown.

Desktop (please complete the following information):

• OS: macOS
• Browser: Chrome

Additional context

I think it is a caching issue, we might need to have a content hash that forces a refetch if the content is changed.

[dosubot]

The caching issue you're experiencing in Hephaestus, where an old version is displayed even after deploying a new one, might be related to how caching is currently implemented. In Hephaestus, caching is managed using Spring's caching annotations. The MetaService class uses the @Cacheable annotation to cache the result of the getContributors method, and cache invalidation is controlled by the @CacheEvict annotation, which clears the cache at a fixed rate ^[1].

To address the issue of serving outdated versions, you might consider implementing a content hashing strategy. This would involve generating a unique hash for each version of the content, which can be used to force browsers and other clients to refetch the updated content when a new version is deployed. This approach ensures that any changes in the content result in a different hash, prompting a cache refresh.

Additionally, reviewing the current cache control headers and how they influence browser caching could help in ensuring that the latest version is always served. Adjusting these headers to better manage cache expiration and validation might also be beneficial.

To continue talking to Dosu, mention @dosu.

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