Change pmtiles serve to keep track of etag from the initial root request on remote archives (HTTP or S3) and make all subsequent requests to that archive with If-Match: ${root_etag}. If any of those requests fail with a 412 or 416 http status code (the remote archive changed) then purge all entries from the cache with that etag and refetch the root and any directories needed for that request at most once.
Followups not included in this PR:
[ ] dedicated file handler that doesn't use gocloud
[ ] integration test in CI that spins up minio and runs tests where the file changes against that
[ ] handle azure etags
[ ] prometheus counters to track etag reload events
Change
pmtiles serveto keep track of etag from the initial root request on remote archives (HTTP or S3) and make all subsequent requests to that archive withIf-Match: ${root_etag}. If any of those requests fail with a 412 or 416 http status code (the remote archive changed) then purge all entries from the cache with that etag and refetch the root and any directories needed for that request at most once.Followups not included in this PR:
Fixes #17