Proxy Cache dependency on upstream registry?

[strowi]

Hi,

just came across this thought - does the proxy-cache in harbor work if the upstream registry is not available (e.g. still serve
already cached images; like Gitlabs dependency-proxy)?
Not sure how the failed HEAD-request is being handled by harbor?

Or would i need to create a full mirror?

regards,
strowi

[chlins]

@stonezdj Please help to confirm this, thanks.