UpdateFetchOutcome

public static final int CACHE_HIT = 1

The request was satisfied immediately from the local cache.

This outcome occurs when the cached data is considered fresh (e.g., it was last updated within the freshness threshold) and no network locks needed to be acquired. This represents the "Fast Path" for the service.

public static final int COALESCED = 2

The request was satisfied from the local cache after waiting for another thread to complete a network fetch.

This outcome occurs when multiple clients request updates simultaneously (a "thundering herd"). The current thread waited for the fetchUpdates lock, and by the time it acquired the lock, another thread had already refreshed the cache. This is considered a "Slow Path" outcome due to the lock wait time, even though no network call was made by this specific thread.

public static final int FAILED = 5

The operation failed with an exception.

This outcome occurs if an unhandled exception was thrown during any part of the update check lifecycle (e.g., network failure, disk I/O error, or rate limiter error). The service returned cached data to the client to prevent the crash from propagating.

public static final int FETCHED = 3

A network fetch was performed and fresh data was returned.

This outcome occurs when the cache was stale, the rate limiter allowed the request, and the UpdateInfoService.fetchUpdates implementation successfully retrieved new data from the backend. This represents the "Slow Path" for the service.

public static final int THROTTLED = 4

The request was blocked by the rate limiter.

This outcome occurs when the cache was stale, but the rate limiter determined that a network fetch should not be attempted (e.g., because a check was performed too recently). The service returned cached data to the client to ensure graceful degradation.