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Clarify the routing algorithm

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Loïc Hoguin 2020-05-20 10:53:52 +02:00
parent 0d0e7d164c
commit 78b23ddfa5
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23
doc/src/guide/routing.asciidoc
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@ -6,9 +6,26 @@ Cowboy does nothing by default.
To make Cowboy useful, you need to map URIs to Erlang modules that will
handle the requests. This is called routing.
When Cowboy receives a request, it tries to match the requested host and
path to the configured routes. When there's a match, the route's
associated handler is executed.
Cowboy routes requests using the following algorithm:
* If no configured host matches the request URI, a 400 response
is returned.
* Otherwise, the first configured host that matches the request
URI will be used. Only the paths configured for this host will
be considered.
* If none of the configured paths found in the previous step
match the request URI, a 404 response is returned.
* Otherwise, the handler and its initial state are added to the
environment and the request continues to be processed.
NOTE: It is possible to run into a situation where two hosts match a
request URI, but only the paths on the second host match the
request URI. In this case the expected result is a 404 response
because the only paths used during routing are the paths from
the first configured host that matches the request URI.
Routes need to be compiled before they can be used by Cowboy.
The result of the compilation is the dispatch rules.