# pacredir - request flow

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Whenever `pacman` sends a request to `pacredir` a number of requests (increasing with the number of hosts found) is sent through the network. Let’s assume `pacredir` knows about two hosts.

## OK - serving from local network

In this exemple one hast (`host A`) is missing the file, but second one (`host B`) does have the file.

For database files the decision on what return code (`307` vs. `404`) to send is made on the file age. The local file’s timestamp is compared to what timestamp `pacman` sends in its request.

After the initial request `pacman` is redirected to `host B` and gets the file there. No request is sent to the mirror.

## FAIL - fallback to mirror

In this example no host has the file or the local database files are older than what `pacman` requested.

All requests made by `pacredir` are answered with http code `404`, thus `pacman` receives the same. Finally `pacman` falls back to the next mirror.

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