Remove repository config caching logic - #410
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Signed-off-by: Alec Scott <alec@llnl.gov>
Signed-off-by: Alec Scott <alec@llnl.gov>
Signed-off-by: Alec Scott <alec@llnl.gov>
Signed-off-by: Alec Scott <alec@llnl.gov>
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Signed-off-by: Alec Scott <alec@llnl.gov>
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this is a nice simplification
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For a long time, the one sticking point when thinking about how to scale Hubcast to multiple Kubernetes replicas had been the repository config cache. Caching repository configs seemed like an obvious win. But with multiple replicas, only one replica would receive the config update event and the others could keep syncing events against a stale config for up to 30 minutes.
Ultimately the simpler answer is that the cache isn't worth its complexity. GitHub grants apps 5000 requests/hr per installation and we're no where near that limit. Additionally we already hit GitHub on every event either by responding to a comment or by fetching a packfile so removing the cache doesn't introduce another point of failure.
As such this PR proposes the kinda radical idea to remove the repository config cache entirely. Instead every event reads the current config so all replica pods are always consistent.
If we ever get close to the 5,000 req/hr/installation limit we could swap to using conditional requests. GitHub returns an ETag header on API responses; sending it back via If-None-Match yields a 304 "Not Modified" when the content hasn't changed. Also 304 responses don't count against the rate limit. Since repo configs change rarely, nearly all config fetches would be 304 responses and wouldn't count against our limit.