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  • Yorick Peterse's avatar
    Refactor cache refreshing/expiring · f10e7ac7c903
    Yorick Peterse authored
    This refactors repository caching so it's possible to selectively
    refresh certain caches, instead of just expiring and refreshing
    everything.
    
    To allow this the various methods that were cached (e.g. "tag_count" and
    "readme") use a similar pattern that makes expiring and refreshing
    their data much easier.
    
    In this new setup caches are refreshed as follows:
    
    1. After a commit (but before running ProjectCacheWorker) we expire some
       basic caches such as the commit count and repository size.
    
    2. ProjectCacheWorker will recalculate the commit count, repository
       size, then refresh a specific set of caches based on the list of
       files changed in a push payload.
    
    This requires a bunch of changes to the various methods that may be
    cached. For one, data should not be cached if a branch used or the
    entire repository does not exist. To prevent all these methods from
    handling this manually this is taken care of in
    Repository#cache_method_output. Some methods still manually check for
    the existence of a repository but this result is also cached.
    
    With selective flushing implemented ProjectCacheWorker no longer uses an
    exclusive lease for all of its work. Instead this worker only uses a
    lease to limit the number of times the repository size is updated as
    this is a fairly expensive operation.
    f10e7ac7c903