Phoenix - New Route from User Input - Adding Route Programmatically

I was thinking about simple user settings for Permalinks.
Something like Wordpress has:

The question is - how to make same behaviour in Phoenix ?
In case of predefined route structures - everything is clear, you simple make predefined routes in advance.

But what about custom one ?

  • How to make a new route structure from user input ?
  • How to add a new route programmatically ?

To my understanding the routes are build during compilation time, but does it mean it is not possible to create during runtime ?

If so then, what would the solution ?

  • Load routes from DB during compilation time and then if new routes are added - restart everything ?

Any ideas or an advice is very much welcome !


Just a thought off the top of my head. The Phoenix Router is “just a plug”. It tends to be the Plug at the end of the pipeline, but it is still a Plug. So it seems you could develop a Plug that looks up a new route in a dynamic data source (an ETS table, or database).

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Thank you for reply!
I was thinking this way too…
I already tried to create a Plug and added that to the Pipeline.
I thought that I can analyse requested url and match through the regexp.
Once matched forward it to required function (handler).

But the problem is the following:

  • it gives the error, something like undefined route and gives me a list of valid routes.

I suppose the question is - during Plug execution, how to connect to the point when Phoenix analyses existing routes and give it the new route taken from DB or User Input ?

You cannot use the Router of plug or phoenix for the routing in this case. You need to create a wildcard route, which simply matches any url that finds it’s way to your endpoint and use custom plug to implement the routing to controllers or whatever needs to receive the request if the url is valid. The routers of plug and phoenix are based on compiled pattern matching functions, so they cannot be dynamic (or even support regex).

Thank you for reply.
I understand that I cannot use that as I already tried without success.
I would prefer not to create a wildcard route due to performance issues.

The question is - how to achieve the desired behaviour without losing performance.

  • It is possible to restart Router independently of Phoenix - I mean recompile it live ?
  • Just that peace of functionality, not the whole Phoenix ?


There wouldn’t be any performance issues if done correctly. I have a plug for webhooks that are generated at runtime to which I forward from the phoenix router module.

It works roughly like this

# in the router.ex
scope "/" do
  # ...
  forward "/webhooks", MyAppWeb.Plugs.WebHooks

# in plugs/web_hooks.ex
def call(%Plug.Conn{path_info: path_info, params: params} = conn, _opts) do
  if handler = get_webhook_handler(path_info) do
  send_resp(conn, :ok, [])

Do you have performance issues? If not I’d not worry to much until you have. If you do then what have you tried?

No, I don’t currently have that.

I just remember there was a post by Chris McCord stating that using a wildcard route would lead to performance problems.

Thank you very much for your example, I really appreciate it !

Probably this is something I should use for now, and if there would be any issues, then look for something else.

One more time, thank you everyone for help !

A Plug accepts a Plug.Conn and returns a different Plug.Conn resource.

Part of the Plug.Conn structure is the “path_info”. Your plug could look at the Path Info and decide what function to call, pass he connection to it, and halt the propagation of the connection (so the the router never sees it).

Or, it could return a new Plug.Conn, with different path_info, let it propagate to the router, and the router could use its regular mechanism on the new path_info.


Thank you easco!
I will try both ways and later reply what is feets more.

Not if you use it at the end of the router I’d think, just have it catch anything not yet caught.

Why not just make a path that does get /p/:id, ... for some short ID though?

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I think you misinterpreted. You may be thinking of responses I have had to folks asking for matching on regex patterns as “wildcards” as me denying those kinds of matches because that would be much slower since we can’t pattern match, but a wildcard match, ie get "/*" or get "/foobar/*" will be super fast and just as fast as any other route match. As other have said, you can get what you by a either a wildcard forward match in the router, followed by your own custom lookup and dispatch code, which calls the appropriate controller (or plug), ie