--- title: Subdomain routing in Rails slug: subdomain-routing-in-rails published_at: 2022-07-25 10:00:13 +0000 updated_at: 2026-03-04 20:13:28 +0000 summary: description: Code:https://github.com/cjavdev/auth0-demo Pre-cursor to setting up multi-tenant auth with auth0. #rails #rubyonrails tags: [cjav_dev, web development tutorials, web development for beginners, vim, ruby, rails, javascript, subdomains, routing, routes, custom domains, domains, dns, ruby on rails, ruby on rails 2022, ruby on rails tutorial, web development tutorial, ruby on rails project, learn ruby on rails, ruby on rails 7, @cjav_dev] views: 3010 author: CJ Avilla url: https://www.cjav.dev/videos/subdomain-routing-in-rails youtube_url: https://www.youtube.com/watch?v=T1pSiWOf0O4 youtube_id: T1pSiWOf0O4 embed_url: https://www.youtube.com/embed/T1pSiWOf0O4 thumbnail_url: https://i.ytimg.com/vi/T1pSiWOf0O4/hqdefault.jpg type: video --- # Subdomain routing in Rails *Published: July 25, 2022* *Views: 3010* ## Watch [Watch on YouTube](https://www.youtube.com/watch?v=T1pSiWOf0O4) [![Subdomain routing in Rails](https://i.ytimg.com/vi/T1pSiWOf0O4/hqdefault.jpg)](https://www.youtube.com/watch?v=T1pSiWOf0O4) ## Description Code:https://github.com/cjavdev/auth0-demo Pre-cursor to setting up multi-tenant auth with auth0. #rails #rubyonrails ## Transcript all right we've got a little application that has auth 0 set up in this episode we're going to add some custom domain or sub domain routing for our rails application so typically when you are testing locally we use this thing called localhost so localhost and all domains you can actually replace with some ip address that that that that domain would resolve to otherwise and so the same in the same way that we can type localhost we could also type 127.0.0.1 that happens to be the local ip address that's like your loopback ip address that is the ip address of your machine and when we say port 3000 we're saying look for the program that's running on or that is bound to port 3000 and let's talk to that program and so if instead of putting 127.0.0.1 we can put in localhost right and localhost happens to be set up as a way as like an alias for one two seven zero zero one and so if we were to look in our if we were to cat etsy hosts this is a hosts file that includes your local mapping between an ip address and a name so inside here you can say sudo vi etsy hosts and this will open up your host file so that you can edit it you have to use sudo and enter in your root password because this hosts file is uh is like i don't know it's it has higher level permissions and so you have to like authenticate in order to edit this because you're messing around with dns now what you can do is copy a domain name in here to whatever you want and make that what your local machine should resolve as so we could say i don't know boogers or something here and then close this out and now if we go to boogers local localhost 3000 that should theoretically oh so it does resolve but for our rails app we would need to go to our hosts um here and say config.hosts allow boogers and uh that we probably need to restart our app and okay so now that works on boogers3000 right so you can basically come up with whatever like local name you want for these hosts um but what can be kind of annoying is when you're working with localhost or boogers these are just a single word right and so that might be i don't know what it's actually called but that's kind of like a tld or a top level domain but when we're working on sub domain routing instead of having something like test.localhost this would mean that dot localhost is the top level domain so that's going to be like our dot com or dot net or dot org or whatever and so then test does not become technically a sub domain test dot local host would be kind of like the domain or the host name and so in order to do something like test.example.com what we want to do is create a local domain that resolves to 1 1 2 7 0 0 1 that is actually like a domain that we can add subdomains to so that we can add subdomain routing so i think if we say nslookup lvh.me let's see so um yeah so this is going to come back as 1 2 7 0 0 1. i think this is actually registered so we can use dig lvh.me i want to say it's actually registered somewhere as a loopback address i don't know who owns this but um yeah you can also you might need to like flush your dns cache whatever like look around but one of the things that can be handy is instead of using localhost if we use lvh.lvh.me colon3000 again we need to like update our hosts file um here so we're going to go to our sorry application we need to update the allowed host so this is something that rails adds in order to protect uh against certain i don't know security things so you can add a list of hosts in here so we might say you know localhost or lvh.me or whatever or what you can do is you can just disable this security check completely by setting it to nil that's like i don't know whatever probably not advised but that's what we're going to do for this demo if you have just a small set of sub domains then you probably want to add all of those or a small set of domains you want to add all of those so that you have a specific list in the case where you're going to let users define what their domains are though you'll have to disable that and then add your own sort of domain checking and ownership of certain domains etc et cetera okay so now that we've disabled that check and we are able to route to lvh.me what we want to do is open up our routes file and inside here recall that we have sort of some get routes for authentication what i want to do is add a new concept called a site this is going to be like a website where users can sign up and then they can create their own sites and each of those sites has its own login to the site and so initially i'm just going to assume that i'm the only user and we're going to ignore logging into our like dashboard or control application and we're only going to think about okay let's create sites with custom domains that other users can log into hopefully that's clear i don't know if it is so like consider maybe we have we want to be able to spin up a site for dog grooming or we want to set up a site for childcare we want to set up a site for this landscaping business so let's create a model railsg model and we'll call it site and this site is going to have some subdomain subdomain and it might also have a custom domain eventually but let's just stick with subdomains for now let's also give it a name and then we're going to have like a maybe like background color and a primary color we could even have like logos and whatever but for now let's just uh let's go with this the one other thing that i'm thinking about in the future that we're going to want is an org for auth0 so i'm going to add an auth auth0 org id we'll come back and we'll talk about that in just a minute but for now we're just going to create a site model so railsdb migrate and what happens when we create a new site is we are going to um use that site's subdomain as routing to see the details of the site so for now let's say railsgcontroller cites and we'll have an index and we'll have a show okay so in the sites index here we're just going to have a list of all the different sites so we're going to say at sites.each do site and for each one we'll link to um and this link is going to go to the like site dot url and we haven't we haven't defined that yet so we'll need to define it um and actually the name of it is going to be like site dot name or whatever okay all right slash ul and i guess we probably also want like a way to create a new site and this will be a form action is going to go to sites method is post and we're going to have our input type is hidden for our authenticity token and for now um we want a name that's right let's actually also add bundle add annotate bundle exec annotate models i like to see um yeah i like to see the the columns as i'm building out the inputs here so i'm going to have an input we'll have an input for the uh the subdomain this placeholder is going to be like sub dot site.com or whatever well just sub yeah sub or i don't know www whatever that www is a special sub domain but yeah we'll figure it out okay then we have our name we have our background color and a primary color and i think that should be it i thought is there an input type color uh for html let's see yeah there is okay let's see how that works color all right so we should be able to create a site like this so let's go back to our routes and we should have resources resource resources sites and we'll come over to slash sites and there's no method for sites is going to be cited at all for now okay so this is going to give us our list of sites slides slash new should bring us to our new form okay so we have here is this is going to be our subdomain so let's say test and our name is going to be test and that's going to be here's our our background color will be i don't know that and then our primary color will be some sort of like blue and then we'll click on create site create doesn't exist site site dot new site params we're going to permit the name subdomain background color primary color and i think that's it if at site dot save redirect to at site otherwise uh render new sure okay so test test make this this color make this this color create site okay now we're seeing the show page so let's go back to our show page and for now we'll just say div class is back or style uh background color is this going to work um cite that background color okay oh no i need to use this the same brace style so like this um undefined method background color for nil so we need to go back to our show our our sites controller here uh site is okay so now we've got a background and we have um the name of our site in the subdomain so what i want to do now is i want to make it so that i can see this exact same content when i go to test.lvh.me like to the root of test.lvh.me and so um let's go back into our our routes and the way that we're going to do this is using this thing called a constraint so um actually inside of these rails routes get is a type of constraint format is a type of constraint resource resources these are all um like helpers that are in order to narrow down the path or look at the request to determine which controller should be handling that request so we can say constraint subdomain and this is just going to be test we'll like hard code it to the one that we just created um and here we can actually say like get or like root and this is going to be our sites show and we're going to say this is going to be as our like site root okay so if i refresh the page here i'll put this one at the bottom so it doesn't match first okay couldn't find a site without id all right so what's happening is we are hitting the show route for our sites controller that's great that's exactly what we want but instead of rendering the details for the site what we're doing is we're trying to look it up by params id but there is no params id so we need to go back to our site's controller and inside the show route here we need to find it by either the params id or by something else so if at site.nil at site is equal to site.find by subdomain is request.subdomain so now if we refresh oh find by so by default find is going to raise an exception that will cause a 404 but we don't want it to raise we wanted to just say we want to return quietly a nil value um okay so now we are able to go to test.lvh.me and we can see the details for the site so this is pretty cool uh so now we yeah so like what we could do is we could put all of like any site routes or anything if we wanted to have certain pages that are related to a site we could nest all of those under like a site's namespace and have it just work um kind of under the site path so this is kind of the the bare bones basics for setting up um a subdomain routing but you'll notice like if we go back to um lvh.me slash sites oh undefined method url for site test okay so let's go back to our site method and say def url is going to be um site root where the sub domain is subdomain let's see if this works undefined methods site root oh right because we need um yeah let's do it inside of the view so root or site index so this should be instead of site url we're going to say site url for subdomain site.subdomain let's see if that works uh no route matches controller site missing okay site oh site root site root url okay so now we have these this this is our list of sites and we have one we click on it we're brought to the test.lvh.me let's make a new site site slash new and we'll say another another and we'll give this one a darker background and a i don't know yellow text create site okay here's our another site right and um we're able to see it here under the sites to path but if we went to just sites if we clicked on another that's bringing us to another.lvh.me and why are we not able to see it that's interesting oh right okay so what's happening is this is the route right because our subdomain constraint in our routes this is only showing us the sites page for the test subdomain so we need to make this a little bit more complex or more sophisticated so what we're going to do is we're going to go into the lib directory we're going to add a new thing called constraints a directory called constraints um constraints and in here we'll say subdomain dot rb sub domain dot our b class actually probably should be called subdomain constraint class sub sub domain constraint and we're gonna say matches so if it basically for um these constraints are the the constraints helper method here accepts either a hash where the key is a value that's part of the request and the value is something to match on or you can pass this a lambda expression or you can just pass it a class that respond or an instance of an object that responds to the matches method so subdomain constraint.new so by saying subdomainconstraint.new this is going to use this instance of the subdomain constraint and call matches on it and this will have the request so we can say something like okay if the subdomain is present and the subdomain well no wait hold on request that subdomain we want to see if there's a site site dot where subdomain yeah so if a s if a site exists where the subdomain matches the subdomain in the um in the request then we're good we could probably make this more sophisticated and build in some caching or something but for now this is uh this is fine so now when we refresh over here for another we might need to restart the server i can't remember okay yeah we need to because we created this new directory and stuff we need to restart the server we might also need to right okay so we also need to um require this file inside of our routes so we're going to say require constraints slash sub domain constraint okay and then we should be able to fire this up i think all right the rails server started and we can refresh the page uh wrong number of arguments uh i guess this takes in the request one given zero expected i just changed oh because you know what uh i think maybe it's not reloading the stuff okay there we go it was not reloading the stuff that's in that lib directory i think all right so another lvh.me now we can see this site very cool so now we have we kind of like have at our top level we have lvh.e sites and we can go to the test site we can go to another site and you could imagine building out custom pages for these based on those different colors and things okay the next step here is we want to combine what we did in the last episode setting up login and log out so that we can support logging into one of these different sites um so maybe you can log in to test but you should not be able to log into another or vice versa or you know perhaps like like i said in the beginning right maybe we have a dog grooming site and that has 20 users and they all have dogs and we have separately a landscaping site and that has 20 users and maybe two of them also are in the dog grooming site but they don't have like you're not going to like log in with the same login necessarily so we want to make it possible so that people can sign up and authenticate to both of those different sites and so this is giving us sort of like this multi-tenant solution inside of rails and so what we want to do is we're going to go and update our authentication or our off zero flow so that it handles this multi-tenant auth so we're gonna do that in the next episode but this was uh hopefully this was a good uh primer in terms of setting up subdomain routing inside of rails and uh yeah stay tuned we're gonna get into the next one shortly all right thanks for watching we'll see in the next one [Music] --- [Back to all videos](https://www.cjav.dev/videos) 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