1 files changed, 38 insertions, 0 deletions
diff --git a/FLOW.md b/FLOW.md
new file mode 100644
index 0000000..7fd1f9b
--- /dev/null
+++ b/FLOW.md
@@ -0,0 +1,38 @@
+pacredir - request flow
+=======================
+
+[◀ Go back to main README](README.md)
+
+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.
+
+![OK - serving from local network](FLOW/ok.svg)
+
+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.
+
+![FAIL - fallback to mirror](FLOW/fail.svg)
+
+All requests made by `pacredir` are answered with http code `404`, thus
+`pacman` receives the same. Finally `pacman` falls back to the next mirror.
+
+---
+[◀ Go back to main README](README.md)  
+[▲ Go back to top](#top)