fix(detector/vuls2): prevent redundant parallel DB downloads in server mode - #2617
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maxenced wants to merge 1 commit into
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fix(detector/vuls2): prevent redundant parallel DB downloads in server mode#2617maxenced wants to merge 1 commit into
maxenced wants to merge 1 commit into
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…r mode When multiple HTTP requests arrive while the vuls2 database is stale, each one independently triggered a full download from the OCI registry. This wasted bandwidth and I/O without any coordination. Introduce a single-flight background fetch mechanism: the first request that detects a stale DB spawns an async goroutine to download the update while immediately serving from the current (stale) DB. All concurrent requests that arrive while the download is in flight skip the fetch and use the existing DB. Synchronous (blocking) downloads are preserved for cases where the current DB cannot be used at all: first-ever download or schema version mismatch. Safety guarantees are maintained: if the background fetch fails, temp files are cleaned up by the upstream fetch library and the lock is released so the next request can retry.
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As discussed in #2613 , vuls2 has no limit on concurrent download when multiple HTTP requests arrive while the vuls2 database is stale, each one independently triggered a full download from the OCI registry. This wasted bandwidth, disk and I/O without any coordination.
This introduce a single-flight async background fetch mechanism: the first request that detects a stale DB spawns an async goroutine to download the update while immediately serving from the current (stale) DB. All concurrent requests that arrive while the download is in flight skip the fetch and use the existing DB.
This does not fix startup download (which will be part of another PR)
Safety guarantees are maintained: if the background fetch fails, temp files are cleaned up by the upstream fetch library and the lock is released so the next request can retry.
Is this ready for review?: YES