LocalCache: reload cached certificates due for renewal from storage - #408
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mbardelmeijer wants to merge 1 commit into
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LocalCache: reload cached certificates due for renewal from storage#408mbardelmeijer wants to merge 1 commit into
mbardelmeijer wants to merge 1 commit into
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The local cache only changes when this instance reads or writes it, so it never learns of a renewal done by another instance. That is fine while the stale certificate is the one being served: it enters its renewal window, and the renewal path reads storage and picks up the peer's renewal. With several issuers it can go unnoticed indefinitely. An expired certificate from the preferred issuer in the local cache loses to a fallback issuer's certificate that is still valid, which is served and never triggers a storage read, while storage holds a renewed preferred certificate the instance never sees. A cached certificate due for renewal is exactly the one a peer is likely to have replaced, so read that issuer from storage instead. The read refreshes the local copy, so it is paid once per renewal; certificates that are not due are still served locally without touching storage.
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Follow-up to #402.
The local cache only changes when this instance reads or writes it, so it never learns of a renewal done by another instance. With a single issuer that heals itself: the stale certificate enters its renewal window and the renewal path reads storage. With several issuers it can go unnoticed indefinitely: an expired certificate from the preferred issuer in the local cache loses to a still-valid fallback certificate, which is served and never triggers a storage read, while storage holds a renewed preferred certificate the instance never sees.
A cached certificate due for renewal is exactly the one a peer is likely to have replaced, so
loadCertResourcenow reads that issuer from storage instead. The read refreshes the local copy, so it is paid once per renewal; certificates that are not due are still served locally without touching storage. If storage cannot be read, the cached copy is served as before.TestLocalCacheStaleCertRenewedByPeerreproduces the two-issuer scenario and fails without the fix.