Author Archives: Jason Swett

Where to start with introducing TDD to a new Rails app

A Code With Jason reader recently wrote me with the following question:

How do I introduce TDD into a new Rails app? Where do I start? I am deeply knowledgable on RSpec and use it a lot. I am not sure how to get started with testing in Rails. When should testing be introduced? (hopefully as soon as possible) What should be testing vs. what should I assume works because it was tested in some other way? For example, why test generated code?

There are a lot of good questions here. I’ll pick a couple and address them individually.

How do I introduce TDD into a new Rails app?

This depends on your experience level with Rails and with testing.

I personally happen to be very experienced with both Rails and testing. When I build a new Rails application, I always start writing tests from the very beginning of the project.

If you’re new to Rails AND new to testing, I wouldn’t recommend trying to learn both at the same time. That’s too much to learn at once. Instead, get comfortable with Rails first and then start learning testing.

What if you’re comfortable with Rails but not testing yet? How do you introduce testing to a new Rails app then?

I would suggest starting with testing from the very beginning. Adding tests to your application is never going to be easier than it will be at the very beginning. In fact, retroactively adding tests to an existing application is notoriously super hard.

The kinds of tests to start with

What kinds of tests should you add at the beginning? I would recommend starting with acceptance tests, also known to some as integration tests, end-to-end tests or, in RSpec terminology, feature specs. The reason I recommend starting with feature specs is that they’re conceptually easy to grasp. They’re a simulation of a human opening a browser and clicking on things and typing stuff.

You can start with a feature spec “hello world” where you just visit a static page and verify that it says “hello world”. Once you’re comfortable with that, you can add feature specs to all your CRUD operations. I have a step-by-step formula for writing feature specs that you can use too.

Once you’re somewhat comfortable with feature specs, you can move on to model specs.

Testing vs. TDD

I’ve been sloppy with my language so far. I’ve been talking about testing but the question was specifically about TDD. How do you introduce TDD into a new Rails app?

First let me say that I personally don’t do TDD 100% of the time. I maybe do it 60% of the time.

I mainly write two types of tests in Rails: feature specs and model specs. When I’m building a new feature, I often don’t know exactly what form the UI is going to take or what labels or IDs all the page elements are going to have. This makes it really hard for me to try to write a feature spec before I write any code. So, usually, I don’t bother.

Another reason I don’t always do TDD is that I often use scaffolds, and scaffolds and TDD are incompatible. With TDD you write the tests first and the code after. Since scaffolds give you all the code up front, it’s of course impossible to write the tests before the code because the code already exists.

So again, the only case when I do TDD is when I’m writing model code, and I would guess this is maybe 60% of the time.

How, then, should you start introducing TDD to a new Rails app? I personally start TDD’ing when I start writing my first model code. The model code is often pretty trivial for the first portion of a Rails app’s lifecycle, so it’s usually a while before I get into “serious TDD”.

What should I be testing vs. what should I assume works because it was tested in some other way? For example, why test generated code?

I’ll answer the second part of this question first.

Why test generated code?

I assume when we say “generated code” we’re mainly talking about scaffolding.

If you’re never ever going to modify the generated code there’s little value in writing tests for it. Scaffold-generated CRUD features pretty much always just work.

However, it’s virtually never the case that a scaffolded feature comes out exactly the way we want with no modification required. For anything but the most trivial models, a little tweaking of the scaffold-generated code is necessary in order to get what we need, and each tweak carries a risk of introducing a bug. So it’s not really generated code. Once a human starts messing with it, all bets are off.

That’s not even the main value of writing tests for generated code though. The main value of the tests covering generated code (which, again, is rarely 100% actual generated code) is that the tests help protect against regressions that may be introduced later. If you have tests, you can refactor freely and be reasonably confident that you’re not breaking anything.

Having said that, I don’t try to test all parts of the code generated by a scaffold. There are some things that are pointless to test.

What should I test and what should I assume works?

When I generate a scaffold, there are certain types of tests I put on the scaffold-generated code. I have a step-by-step process I use to write specific test scenarios.

I typically write three feature specs: a feature spec for creating a record using valid inputs, a feature spec for trying to create a record using invalid inputs, and a feature spec for updating a record. That’s enough to give me confidence that things aren’t horribly broken.

At the model level, I’ll typically add tests for validations (I am TDD’ing in this case) and then add the validations. Usually I only need a few presence validations and maybe a uniqueness validation. It’s not common that I’ll need anything fancier than that at that time.

There are certain other types of tests I’ve seen that I think are pointless. These include testing the presence of associations, testing that a model responds to certain methods, testing for the presence of callbacks, and testing for database columns and indexes. There’s no value in testing these things directly. These tests are tautological. What’s better is to write tests for the behaviors that these things (i.e. these associations, methods, etc.) enable.

Suggestions for further reading

Extracting a tidy PORO from a messy Active Record model

Skinny controller, fat model – the old best practice

In 2006 Jamis Buck wrote a famous post called Skinny Controller, Fat Model. In it Jamis observed that Rails developers often put too much logic in controllers, making the code harder to understand and to test than it needs to be.

“Skinny controllers, fat models” became a piece of accepted wisdom in the Rails community. I think it was a genuine step forward in the overall state of affairs.

The new best practice: skinny everything

But over time developers apparently came to a realization that while it’s better in certain ways to put bulky code in models than in controllers, the fatness, wherever you put it, is still kind of a problem.

Other ways of combating digital obesity were adopted or devised, including concerns, service objects, domain objects, Interactors, factories, something called Trailblazer, and probably others.

Not all weight loss methods are equally good

When we talk about making e.g. a controller less fat, we of course aren’t talking about obliterating the bulk from existence but rather just moving it to a more appropriate place. The world is complex and we can’t make the complexity go away. The art is in distributing the complexity throughout the code such that a human can understand what the application does, in spite of the complexity.

For whatever reason, it seems lately that “service objects” (a term which means different things to different people, hence the quotes) and Interactors are widely esteemed as great ways to reorganize complexity in a Rails application. I personally find Interactors and service objects unappealing. In fact, I think they’re terrible. Avdi Grimm seems to have a similar opinion.

I think service objects and Interactors add unnecessary complexity to an application without adding any meaning to justify their added complexity. To take every action and make an object named after it—e.g. AuthenticateUser, PlaceOrder, SendThankYou—seems like a superfluous, tautological extra step. I think we can do better.

The case for POROs and domain objects

In Domain Driven Design, Eric Evans describes the concept of domain objects, which I take to mean: objects that represent concepts from the domain.

To me this makes a lot of sense. Most Rails applications of course already make use of this concept. If there’s something called an appointment in the domain, there will be an Appointment class in the application. If there’s something called a Patient in the domain, there will be a Patient class in the application.

It’s also possible to invent objects that don’t exist in the domain, that only exist to make the code easier to understand. It took me personally a long time to realize this. Examples of object-oriented programming often include things like creating a Dog and a Cat class, each of which inherit from Animal. These examples seem sensible and straightforward, but think of how many objects in Ruby and Rails have nothing to do with any corresponding real-world idea, e.g. Request, MimeNegotiation and SingularAssociation.

These types of objects take a little extra imagination to conceive of and name, but I think once a person opens up their mind to this way of coding, it gets easier and easier.

The form that I like to give these sorts of objects is POROs (Plain Old Ruby Objects).

My example code: a messy Active Record class

For the remainder of this post I’m going to take a certain big, messy Active Record class and refactor it into some number of POROs.

The code below is taken from a real production application. It was written by a terrible programmer: me in 2012. The class represents a stylist at a hair salon.

I invite you to have a nice scroll through the code and give yourself a light familiarity with it.

The PORO to extract: calendar-related code

The class is so big and the code is so bad that it’s hard to decide where to start. I could spend quite a lot of time refactoring this class, but to make it all fit into a reasonable blog post, I’ll extract just one POROs out of this class.

There are a few methods that I happen to know are related to displaying the stylist’s name on the calendar:

This is relatively easy low-hanging fruit. I can just conceive of a Calendar object and move these methods into it.

This won’t exactly work, though. Many of the values referred to inside this new class only exist in the context of a Stylist. We’ll need to pass in a Stylist instance.

Now that I see this much, I realize I’ve chosen an unfitting name for this class. All this code deals with figuring out where to show the current stylist in a list of all the stylists. There’s no way it makes sense to have a Calendar instance with just one single Stylist inside it. This class name needs to change.

Perhaps CalendarStylistListItem is a better name.

Now I can take a closer look at the contents of this class itself. I’m going to focus on this method first:

Why is salon concerned with highest_manual_order_index? That seems like too fine-grained a detail for it to care about. That also seems like perhaps a responsibility of the CalendarStylistListItem class. Let’s bring it in.

Now I’ll focus on the next method down, alphabetical_position.

Some of this code could certainly be refactored to be tidier, but I don’t see a lot with respect to object composition that needs to change. One thing that does stick out to me is salon.ordered_stylist_names. This seems like a concern of the CalendarStylistListItem, not of the salon. Let’s bring this method in.

In the process of doing this I see one more method that’s currently in Salon that would be more appropriate in CalendarStylistListItem: the has_manual_order? method. Let’s bring that in and rename it to salon_has_manual_order?.

Lastly, I’m pretty sure the only method needed from the outside is order_index. Let’s make manual_position and alphabetical_position private.


The process of creating my PORO, CalendarStylistListItem, didn’t require importing any libraries or learning any radically new techniques. All I had to do was identify a “missing abstraction” in my Stylist class and then conceive of a new object to bundle it up in.

The overall impact to the Stylist class was not all that profound, but cleaning up a big messy class is of course going to take quite a lot of work. I feel like this was a meaningful step in a positive direction.

Next time you encounter a bloated Active Record model, I hope that instead of reaching for a service object or Interfactor, you might consider refactoring to a PORO.

My top five Rails performance tips for performance noobs

Performance is a topic that’s widely discussed and also, sadly, widely misunderstood.

I’m going to share five performance tips that have worked well for me in my 9+ years of using Rails and even before that, since much of what’s here is technology-agnostic.

I want to add a caveat: I’ve never worked for a big B2C startup that has needed to scale to millions of users. I’ve worked mostly applications with modest user bases and modest performance requirements. Luckily, I imagine my career experiences are probably pretty similar to that of most Rails developers, so it’s highly likely that what has worked for me performance-wise will also worked for you.

If you already know the basics of performance optimization and want to hear from someone who does Rails performance work all day every day, I recommend checking out the work of my friend Nate Berkopec, who I know as “The Rails Performance Guy”. (I’ve also had Nate on my podcast.)

Now onto my tips.

1. Don’t optimize prematurely

Before I came to Rails I worked with PHP. At one of my PHP jobs, I worked at a place where our official policy was to use single-quoted strings instead of double-quoted strings. The reason for this policy was that, supposedly, single-quoted strings were parsed ever so slightly faster than double-quoted strings.

In other words, someone in leadership took great care to implement and enforce a policy that was probably responsible for like 0.0001% of the total performance picture for any one of our apps. Penny wise, pound foolish.

Don’t do this. When you’re first building an application, the right approach to performance 99% of the time is to not think about it at all. Unlike bugs, which are best never deployed to production, performance problems are usually best dealt with after they’re discovered in production, after they prove themselves to be legitimate problems.

2. Profile and benchmark before optimizing

When I talk about performance profiling, I mean taking stock of performance across an application and judging where optimization effort is best spent. Some judgment and common sense come into the picture here. For example, if two pages are equally slow, and one of them is visited 100 times a day and the other one 1 time a month, obviously fixing the busier page will give a higher ROI.

In practice I rarely bother to do any actual profiling though. This is partly due to the nature of the work I personally have done historically. Most of my projects have been back-office internal-facing apps where I have a direct line of communication with the users or someone representative of the users. If there’s an important page that’s unacceptably slow, I’ll usually hear complaints about it or I’ll observe the sluggishness firsthand.

The next step I take before setting to work on optimization is to get a benchmark. This is just a fancy way of saying that I measure how fast the page currently loads. I of course can’t know how much of an improvement I made unless I know the difference between the “before” speed and the “after” speed.

The way I typically perform my benchmarking is to simply load a page in my browser while watching the output of the logs in a different window. At the bottom of the log it will say, e.g. “Completed 200 OK in 760ms”. I also use the sql_queries_count gem because sometimes it’s helpful to be aware of how many queries are being executed on the page.

3. The key to performance is usually not to add clever things but to remove stupid things

Performance optimization is often more akin to digging a ditch than to solving a Rubik’s cube.

Typically, the thing responsible for most of the performance cost of a page is waste. There’s a thing that could easily be done in an efficient way, but for whatever reason it was done in an inefficient way. So the task when optimizing a page is to find the waste and remove it. More on this in the next tip.

4. It’s almost always the database

The cause of most performance problems is waste. Most waste takes the form of making too many trips to the database.

This fact is so true and important that, in my 15+ years of programming experience, almost every performance optimization I’ve made has been some variation of “hit the database less”.

In Rails, the most common form of hitting the database too much is the famous “N+1 query problem”. Let’s say you have a page that shows a list of 10 things—let’s say clients—where each list item shows not only the client’s name but the client’s address. This means that a database query occurs for each one of those 10 clients. That’s the N in N+1. The +1 part of N+1 is the original query behind Client.all that grabs all the clients in the first place.

A common solution to the N+1 query problem, one I use a lot is eager loading. Instead of doing Client.limit(10), you can do Client.includes(:address).limit(10), which will grab all associated addresses ahead of time in just one query instead of in 10 separate queries. So instead of a total of 11 queries (1 for all clients, 1 for each of 10 addresses) you’ll have a total of just 2 queries (1 for all clients, 1 for all addresses).

Another way to make fewer trips to the database is to cache the results of expensive queries. I often use Rails’ low-level caching for this. However, this adds a certain amount of complexity that I’m not always eager to add. So I prefer to try to make fewer trips to the databases and/or optimize my queries themselves, resorting to caching only if I have to.

5. If it seems faster, it is faster

The only thing that ultimately matters is how fast users perceive the application to be. If a certain change makes an application feel faster, then for all intents and purposes, it is faster.

I once heard a story about a condo where the residents complained about the elevators being slow. Management’s reaction was not to immediately try to speed up the elevators somehow, which would presumably have been difficult and expensive. Instead, management installed mirrors on the walls next to the elevators. The complaints went away.

So, sometimes the right initial response to a performance problem is not necessarily to embark upon a big, expensive optimization project. Sometimes a change can be introduced that’s less invasive but still effective. For example, let’s say I have a calendar page with back/forward buttons to go from month to month, and let’s say each month takes 800ms to load. If I click the button and nothing at all happens for 800ms, it might feel a little slow. But if I change it so that immediately upon clicking the button I see an animated loading indicator, the page will feel faster. It sounds dumb but it’s absolutely true. Sometimes those little changes that improve the responsiveness of a page will increase its perceived performance, without needing to touch the actual performance at all.

6. Bonus tip: it’s almost never Ruby

Despite what you might read online about Ruby being “slow”, I’ve never ever encountered a performance problem where the culprit was the Ruby language itself. Whether an application is written in Ruby, Go, Python or whatever else, the performance bottleneck is almost always the database.

If all you know about performance is the five tips above, you’ll probably be able to tackle 80% of the performance challenges you encounter.

How to perform hotfixes without side effects or extra stress

A reader of mine recently wrote to me with a question which I’ll paraphrase.

The “tagalong” problem

Let’s say I have a production server. Let’s also say that in addition to that, I have a staging server where I push most changes before production so the changes can be reviewed. This works out fine most of the time.

But let’s say occasionally there’s a critical bug in production that needs to be fixed ASAP. I need to make my fix and push straight to production without the delay of going to staging first. Unfortunately when I do this I also push the last however many commits to production as well.

In other words, as a side effect of my bugfix, I end up pushing work to production that potentially wasn’t ready for production yet.

The fix

The solution is to always keep the master branch in a deployable state. I’ll mention a few tactics that can make this easier.

The first tactic is frequent deployments. I try to do all my work in the form of atomic commits which could each conceivably be deployed to production. And in fact, I tend to perform a deployment almost every time I commit to master or merge something into master.

The second tactic is feature branches. Feature branches help keep partway-done work out of master, helping ensure that a deployment of what’s on master never means deploying incomplete work. In my experience it’s good for a feature branch to have a lifespan of a few hours or a few days. Anything much longer than that gets dangerous because it leaves too much room for the feature branch to diverge from master.

But what if you need to work on a feature that spans, say, 4 weeks, and can’t be released until it’s fully complete? This is where my third tactic comes in, dark launching. Dark launching is where you separate the concept of deployment from the concept of release. Just because the code for a feature gets deployed to production doesn’t mean that that feature necessarily needs to be surfaced to users. The UI of that feature can be hidden using a feature flag, which can be as simple as something that says if false until you’re ready to unveil that feature and remove the code that hides it.

Recommended reading

The things I’ve shared above are basically DevOps principles. To learn more you can check out the books The DevOps Handbook and Continuous Delivery.

Writing software isn’t like building a house, it’s like writing a novel

It’s common to analogize writing software with building a house.

I think it’s a lot more like writing a novel.

With a house, you can add an addition and not necessarily have to change much. But with a novel, everything in it has to reconcile.

The father becomes a mother

Imagine a novel about father who has a troubled relationship with his son because the father spends too much time at the bar, getting in fights and getting fired from a string of jobs due to his irresponsibility. In the end the father dies in a drunken car crash and, fast forward, the son grows up to be just like his father. (Sorry, didn’t mean to make it so dark!)

But then imagine “the requirements change” somehow and the father character needs to be a mother instead.

We can’t just search-and-replace “dad” with “mom”. All sorts of other things need to change as well if the whole thing is going to square up.

If the tragedy of the story is that the son turns out to be just like his father, then maybe a mother-son thing doesn’t really make much sense anymore. Maybe the son has to be a daughter instead. A mother can just as plausibly be an alcoholic as a father of course, but the part about the constant fist fights makes a little less sense now. That part will probably either have to be eliminated or changed to something else.

Every codebase is a novel

Software is of course the same way. Some changes are isolated sometimes, but quite a lot of changes have ripple effects throughout the whole system. And the bigger a codebase gets, the more challenging and time-consuming it is to keep everything self-consistent.

This is why the construction analogy doesn’t really fit all that well. I think the novel analogy is better.

How to set up an RDS database for Rails on EC2

This is part 5 of my series on how to deploy a Ruby on Rails application to AWS. If you found this page via search, I recommend starting from the beginning.

Overview of this step

This is the final step. First we’ll create an RDS database in the AWS console, then we’ll create our actual Rails application database.

Just before we cross the finish line we’ll precompile our assets as the very last step.

1. Create the database

Go to the RDS page in your AWS console. Click Create database.

On the next page, choose PostgreSQL.

Scroll down and select Free tier. If you’re following along with my hello_world repo, set the database name to hello-world. For a password, put whatever you want.

Leave everything else at its default. Click Create database at the bottom.

2. Connect Rails with your RDS database

If you’re using my hello_world app, make note of what’s in config/database.yml under production. If you’re using your own app, set the production section of your app’s config/database.yml to match what’s below.

The above config code reads environment variable values. Elsewhere we need to set environment variable values.

In our nginx config file, /etc/nginx/sites-enabled/default, we need to add the following, under the server section. This will allow nginx to read our env var values.

If you don’t know where to find your endpoint URL, it can be found under Connectivity & security on the detail page for your RDS database, as pictured below.

In addition to nginx being able to read our env var values, we also need the terminal to be aware of our env var values. Unfortunately I don’t know of a way to satisfy both nginx and the terminal in a way that doesn’t involve duplication. To bring the env var values into the terminal, add the following to /home/ubuntu/.bash_profile.

Now execute ~/.bash_profile and echo a value to verify that the env vars have been successfully set.

3. Create the app’s database

Even though we’ve created the RDS database, we still need to create the actual Rails database instance. (The RDS database is more like a container.)

Unfortunately this won’t work. We get an error about Yarn packages. We need to address this, and in order to address this we need to install Yarn.

Now we can install the Yarn dependencies.

And now, finally, we can actually create the database.

4. Precompile assets

Before we check what’s in the browser, let’s tail the logs.

If the database steps were successful, we should now be past any database-related errors. The error we see should be related to assets not being precompiled.

This is easily fixed by running the rails assets:precompile command.

5. Verify success

When you visit your EC2 instance’s URL in the browser, it should now actually work!

If you try to add a person via the form, that should actually work too!

Congratulations. You now have a working Rails application on AWS.

How to set up Rails secrets

This is part 4 of my series on how to deploy a Ruby on Rails application to AWS. If you found this page via search, I recommend starting from the beginning.

Overview of this step

We need to set up the Rails secrets security feature. It’s a relatively simple step although it does require us to jump through a few hoops.

1. Run rails credentials:edit

First we need to give permission to the current user, ubuntu, so we can make changes.

When we run the rails credentials:edit command, it will have us edit a credential file. We need to specify the editor that should be used for this action. In this case I’ll specify Vim.

Now we need to delete the existing config/credentials.yml.enc or else there will be a conflict.

With all these things out of the way, we can finally edit our credential file. No changes to the file are necessary. Just save and exit.

Lastly, we need to give permissions back to the nginx user, www-data. Restart nginx afterward.

2. Verify success

Now, if you visit your EC2 instance’s URL in the browser, you should get this error:

The significant thing about this error is that it’s coming from Rails, not nginx. So we’ve made it all the “to Rails”.

If you run tail -f log/production.log before refreshing the page, you should be able to see the exact error that’s occurring. It should be something like this:

This is telling us there’s no PostgreSQL server running, which is true. We can fix this problem in the next step: setting up our RDS database.

How to add a Rails application to an nginx server

This is part 3 of my series on how to deploy a Ruby on Rails application to AWS. If you found this page via search, I recommend starting from the beginning.

Overview of this step

In this step we’re going to clone our Rails application, make sure the server’s Ruby version matches the application’s Ruby version, and install the application’s dependencies.

1. Clone the application

For the rest of this tutorial I’m going to use a certain Rails application of mine called hello_world. Its repo is public, so feel free to use my app instead of yours for practice if you want.

2. Install the right version of Ruby

When we set up nginx and Passenger in the previous step, we configured the server with Ruby 2.5.

Unfortunately, my hello_world application uses Ruby 2.6.5, so Ruby 2.5 isn’t going to work. We could have configured Ruby 2.6.5 from the start but I didn’t want to add more steps and make things more confusing.

We could install Ruby any way we want but I’m going to use RVM.

3. Configure nginx to use the new Ruby version

Now we need to get the path of the Ruby we just installed.

Copy and paste the Ruby path (for me it was /home/ubuntu/.rvm/gems/ruby-2.6.5/wrappers/ruby) into /etc/nginx/sites-enabled/default.

Here’s what my full /etc/nginx/sites-enabled/default looks like for reference.

4. Bundle install

Before we can serve our Rails app we need to install its dependencies using bundle install. Before we can do that we need to install Bundler.

Also, I’m using PostgreSQL, and in order to successfully install the pg gem, I need to have libpq-dev installed.

Now we can bundle install.

5. Set proper permissions

In order to do its business, the nginx user, www-data, needs to have ownership of our project directory.

6. Verify that this step worked

Lastly, we’ll verify that everything we’ve done so far has worked.

The app can’t be served yet because we haven’t yet done all the necessary steps, so we can’t verify the success of this step by checking to see if the app can be served. All we can do is check to see that the error message we get when we try to serve the app is the error message we expect.

Let’s tail the nginx log file so we can see whatever errors that come across.

Now visit your EC2 instance’s URL in the browser. What will almost certainly happen is you’ll get some sort of error. Below is the expected error.

Error: The application encountered the following error: Missing secret_key_base for 'production' environment

If you see the above error regarding secret_key_base, you’re all set for this step. If you get a different error, there’s a problem.

Now we can move onto the next step, setting up Rails secrets.

How to install nginx and Passenger on an EC2 instance for Rails hosting

This is part 2 of my series on how to deploy a Ruby on Rails application to AWS. If you found this page via search, I recommend starting from the beginning.

Recap of last step and overview of this step

In the previous step we launched an EC2 instance.

In this step we’re going to install some useful software on our new EC2 instance, specifically web server software.

A note before diving in: I must give credit to Passenger docs, from which some of this is directly lifted.

1. Install nginx

The very first step is to install nginx, which luckily involves very few steps.

As a reminder, these commands and all commands that follow are meant to be run on your new EC2 instance. Instructions for how to SSH into your EC2 instance can be found near the end of the previous step.

2. Install Passenger

I recommend executing each of the following groups of commands separately, one at a time. That way it’s easier to tell whether each group of commands was successful or not.

The following step verifies that the config files do in fact exist at /etc/nginx/conf.d/mod-http-passenger.conf. The result of the ls command is supposed to be the file path, printed back out to you (/etc/nginx/conf.d/mod-http-passenger.conf). If it’s not, there’s a problem.

Now we’ll restart nginx to make our changes take effect.

This step validates the Passenger installation.

3. Configure nginx/Passenger to know about Ruby

What follows in this step is roughly copied from this page. If you have trouble or want clarification, I recommend visiting that page to get the info directly from its original source.

The first thing we need to do is find out our Ruby path. Running the following command will tell us. You’ll probably have to look kind of hard because the output of the command is “noisy”. The Ruby path is there but it’s kind of obscured by some other stuff.

Once you’ve found the Ruby path in the output of that command, copy it. We now need to edit /etc/nginx/sites-enabled/default. I use Vim but you can of course use whatever editor you want.

We’ll need to add the following two lines inside the server block. I don’t believe it matters exactly where these two lines go as long as they’re between the two braces of the server block.

If it helps, here’s what my complete /etc/nginx/sites-enabled/default looks like (with comments removed for brevity):

Now we’ll restart nginx to make our changes take effect.

4. Enable port 80 to allow web traffic

Our server is now ready to be visited in the browser, except by default AWS doesn’t have port 80 open, the port for HTTP traffic. Let’s open port 80.

The way we do this is by adding a rule for port 80 to our EC2 instance’s security group.

To do this, first go to to the AWS console, click the EC2 instance, make sure you’re on the Description tab, then click the first link under Security groups.

Then, under the Inbound tab, click Edit.

Click Add Rule, select HTTP from the list, then click Save. The change will take effect right away and HTTP traffic will be allowed starting immediately.

5. Visit the server in the browser

Enter your EC2 instance’s public DNS into your browser. As a reminder, this can be done by going to the EC2 Dashboard, right-clicking your instance, and clicking Connect.

When you visit your server you should see the following page. This means nginx is running!

Now we can move onto the next step, connecting Rails with nginx.

How to deploy a Ruby on Rails application to AWS


This tutorial will show you how to deploy a Rails application to AWS.

There are a number of ways this task could be tackled. It can be done manually or it can be done using an infrastructure-as-code approach, with a tool like Ansible.

This tutorial shows how to deploy Rails to AWS manually.

Before you dive in, be forewarned: it’s kind of a monster of a task. There are a large number of steps involved, many of them tricky and error-prone. Be prepared for the full process to involve hours or even days of potentially frustrating work.


The size of the setup process makes it impractical to put everything into one post, so each step is its own post.

  1. Launch EC2 instance
  2. Install nginx and Passenger
  3. Add the Rails application to the nginx server
  4. Set up secrets
  5. Create RDS database

Don’t be discouraged if not everything works on the first try. It most likely won’t. My advice if something goes wrong is to just blow everything away and start again from the beginning. I find that that approach is, paradoxically, often the fastest.

Good luck!