January 10, 2022·9 min read

Using Upstash Redis with Remix

Leigh HallidaySenior Engineering Manager, Wrapbook (Guest Author)

Remix is a new take on what it means to be a fullstack React framework, focusing on existing web standards and tying the frontend closely to the backend. This tight coupling is a breath of fresh air when you see how simple it is to load data into your React components or how to process data submitted from a form.

In this article we will see Remix's power by creating a simple Feature Flag management system using Upstash Redis as the database.

Full source code can be found here.

Setup

You will get a brand new Remix app by running npx create-remix@latest and choosing your preferred deployment environment. I went with Vercel but it should not make a difference for this tutorial.

There are two ways you can connect to Upstash Redis: The first is through a TCP connection in which you can use any standard Redis client library that you are used to. The second is via Upstash's REST API. We will be going with the second option because it is available in all serverless environments, such as the Cloudflare Workers environment that Remix can be deployed to. Upstash has a package which mimics the actual Redis commands, making it easy to know which function to call.

We now need a way to store two environment variables needed to connect to our Upstash Redis database. Remix doesn't come with development env var support out of the box, but it can be accomplished by adding dotenv as a development dependency.

npm add --save-dev dotenv

In our .env file (which should be added to .gitignore) we can set up two env vars required to connect to Upstash Redis. The @upstash/redis package automatically detects these so there is no need to connect within our code. These values can be found within the Upstash dashboard after creating a new Redis database.

UPSTASH_REDIS_REST_URL="https://..."
UPSTASH_REDIS_REST_TOKEN="..."

We need to update our dev script to have dotenv pick up the env vars. The other scripts can stay the same.

{
  "scripts": {
    "dev": "node -r dotenv/config node_modules/.bin/remix dev"
  }
}

Storing Feature Data

Feature flags can get incredibly complex, with rollout plans to percentages of your userbase, enabled for specific groups of users, but they can also be as simple as "on" and "off". We will be storing our feature flags using the Hash data type that Redis provides. Our data will end up looking like the JSON below, where "1" is enabled/on and "0" is disabled/off".

{
  "chart": "1",
  "graph": "0"
}

To access and manipulate this data we'll use four commands/functions provided by Redis:

hgetall to retrieve all keys (features) and values (enabled/disabled).
hset to enable or disable a specific feature flag.
hdel to delete a specific feature flag.
hmget to get multiple but specific feature flag values at once.

Managing Features

We will be building a page located at /features which is in charge of creating and managing (enable/disable/delete) existing features. We will go into detail about what AddFeature and FeatureList do when we discuss how to load data and then how to write data.

// app/routes/features.tsx
export default function Features() {
  return (
    <div>
      <h1>Features</h1>
      <AddFeature />
      <FeatureList />
    </div>
  );
}

Data Loaders

A data loader is an exported function in Remix named loader which gets run on the server and returns data that is made available to our React component via a hook.

We are starting with a page to create and manage feature flags, and in this case we want to return all the features. They'll be returned as an array of pairs:

[
  ["graph", true],
  ["chart", false]
]

Starting with a TypeScript type definition, we'll then see a function called loadAllFeatures that uses the hgetall function from @upstash/redis.

import { Redis } from "@upstash/redis";
 
type LoaderData = {
  features: Array<[string, boolean]>;
};
 
const loadAllFeatures = async () => {
  const redis = Redis.fromEnv();
  const data = await redis.hgetall("features");
  const features: Array<[string, boolean]> = [];
 
  for (let i = 0; i < data.length; i += 2) {
    features.push([data[i], data[i + 1] === "1"]);
  }
 
  return features.sort((a, b) => {
    if (a[0] > b[0]) return 1;
    if (a[0] < b[0]) return -1;
    return 0;
  });
};

The exported loader function itself will call the loadAllFeatures function, returning the features to be passed into the React component.

export const loader: LoaderFunction = async (): Promise<LoaderData> => {
  // You would want to add authentication/authorization here
  const features = await loadAllFeatures();
  return { features };
};

We'll cover the details of this React component later, but to show how you access the data returned from the loader function, you use a Remix hook called useLoaderData.

const FeatureList = () => {
  const { features } = useLoaderData<LoaderData>();
 
  return (
    <ul>
      {features.map(([feature, active]) => (
        <li key={feature}>{/* coming soon */}</li>
      ))}
    </ul>
  );
};

Form Actions

We've seen how data is loaded, but at this stage we don't actually have any features in our feature flag database! Here is where form actions come into play. Data is processed in Remix by exporting a function named action. Much like loader, this is run on the server and it typically returns json data that the React component can access via another hook, or it can tell the browser to redirect to another page.

The action function below actually handles four different types of actions, creating a feature, enabling/disabling a feature, and deleting a feature. We handle this with a switch statement that then calls the appropriate Redis function/command.

export const action: ActionFunction = async ({ request }) => {
  // You would want to add authentication/authorization here
  const formData = await request.formData();
  const feature = formData.get("feature") as string;
  const action = formData.get("_action") as string;
 
  if (!feature || feature.length === 0) {
    // This isn't currently displayed in our component
    return json({ error: "Please provide a feature" });
  }
 
  switch (action) {
    case "create":
    case "enable":
      await redis.hset("features", { [feature]: 1 });
      break;
    case "disable":
      await redis.hset("features", { [feature]: 0 });
      break;
    case "delete":
      await redis.hdel("features", feature);
      break;
  }
 
  return redirect("/features");
};

You'll notice that on success, I redirect to the same page the user is currently on. This essentially triggers a page reload, calling the loader function and updating what is displayed to the user.

To add a new feature flag, the AddFeature component will use the Remix Form component that will submit the data to the action function we saw above. I specified that it should submit via the post method and also provided the replace prop so that it doesn't add a new page to the browser's history every time we create a feature flag.

const AddFeature = () => {
  return (
    <Form method="post" replace>
      <input type="hidden" name="_action" value="create" />
      <input type="text" name="feature" required placeholder="name" />
      <button type="submit">Add</button>
    </Form>
  );
};

Once a feature has been created, we'll want to show all the current feature flags so they can be managed. Each feature flag actually displays two forms: One to enable/disable the feature flag, and a second to delete it.

Note that there are two hidden fields: _action so that our action function knows what we are trying to do to the feature, and feature which sends the flag name we want to modify.

const FeatureList = () => {
  const { features } = useLoaderData<LoaderData>();
 
  return (
    <ul>
      {features.map(([feature, active]) => (
        <li key={feature}>
          <Form method="post" replace>
            <input
              type="hidden"
              name="_action"
              value={active ? "disable" : "enable"}
            />
            <input type="hidden" name="feature" value={feature} />
            <button type="submit" className="btn-naked">
              {active ? "💪" : "🦾"}
            </button>
          </Form>
 
          <span>{feature}</span>
 
          <Form method="post" replace>
            <input type="hidden" name="_action" value="delete" />
            <input type="hidden" name="feature" value={feature} />
            <button type="submit">Delete</button>
          </Form>
        </li>
      ))}
    </ul>
  );
};

Using Features

We have feature flags in our Upstash Redis database, but what good is that if we aren't toggling functionality on or off in our app based on these flags. We will use a loader function to load specific features from the database using hmget, and then a little data manipulation to get it into the right structure.

If we want to load ["chart", "graph", "fake"] flags, Redis will return us ["1", "0", null]... keep in mind that if the flag doesn't exist, its value will be null, which I wanted to show by including the fake flag.

type LoaderData = {
  features: Record<string, boolean>;
};
 
const loadFeatures = async (keys: Array<string>) => {
  const data = await redis.hmget("features", ...keys);
 
  const features = keys.reduce<Record<string, boolean>>((acc, key, index) => {
    acc[key] = data[index] === "1";
    return acc;
  }, {});
 
  return features;
};
 
export const loader: LoaderFunction = async (): Promise<LoaderData> => {
  const features = await loadFeatures(["chart", "graph"]);
  return { features };
};

We can now access the loaded data in our component, again using Remix's useLoaderData hook. Then choose how the functionality of our website should change given whether a flag is currently enabled or disabled.

export default function Index() {
  const { features } = useLoaderData<LoaderData>();
 
  return (
    <div>
      <h1>Dashboard</h1>
      {features.chart ? <h2>Chart</h2> : <h2>No Chart</h2>}
      {features.graph ? <h2>Graph</h2> : <h2>No Graph</h2>}
    </div>
  );
}

Conclusion

In this article we've seen how to use Upstash Redis to create a simple feature flag system in Remix, taking advantage of its data loader and form action server side functions. These allow us to keep the backend and frontend of a specific page tightly coupled, iterating quickly without the need to set up a separate GraphQL API and override standard form submission events on the frontend. Remix as we've seen leans in to web standards around how forms submit their data.

redis remix serverless