Redis - standalone Redis ServerFind this example at https://github.com/fly-examples/redis/
A key/value database like Redis is useful to have to support caching, session management and, well, anything which needs simple fast storage. That's why there's Redis already built into Fly. But there are some things that Redis configuration doesn't do, like Publish and Subscribe, and that's when you want to deploy your own Redis on Fly.
For this example, we are going to customize a Redis docker image to tune it for running on Fly and deploy it with persistent disk storage for Redis to save its data on.
There's a couple of components to this example. We're going to use the official Redis image,
redis:alpine, but we want to change some system settings before Redis starts running. To do that, we'll use a script,
#!/bin/sh sysctl vm.overcommit_memory=1 sysctl net.core.somaxconn=1024 redis-server --requirepass $REDIS_PASSWORD --bind 0.0.0.0 --dir /data/ --appendonly yes
sysctl calls set up the environment so that Redis doesn't throw warnings about memory and connections. The script then starts up the Redis server, giving it a password to require and a directory to persist into using . Now we need to make those changes apply to a new Redis deployment. For that we use this
FROM redis:alpine ADD start-redis-server.sh /usr/bin/ RUN chmod +x /usr/bin/start-redis-server.sh CMD ["start-redis-server.sh"]
It adds our new shell script to the image, makes it executable, and makes the image start by running that shell script.
With these two files in place we're ready to put Redis onto Fly.
First, we need a configuration file - and a slot on Fly - for our new application. We'll use the
fly init command. The parameter is the app name we want - names have to be unique so choose a new unique one or omit the name in the command line and let Fly choose a name for you.
fly init redis-example
Selected App Name: redis-example ? Select organization: Demo Sandbox (demo-sandbox) ? Select builder: Dockerfile (Do not set a builder and use the existing Dockerfile) ? Select Internal Port: 6379 New app created Name = redis-example Organization = demo-sandbox Version = 0 Status = Hostname = <empty> App will initially deploy to ord (Chicago, Illinois (US)) region Wrote config file fly.toml
The important choices here are we select a Dockerfile (the one we created) as the builder for this app and we set the internal port to 6379, the default port for Redis. Do take note of which region here the init command says the app will initially deploy into. We'll need that in a moment.
This will generate a new fly.toml file which we'll need to edit. By default, the
fly.toml takes the internal port and connects it to an HTTP only handler on port 80 and a combined TLS/HTTP handler on port 443. We don't need that at all, we just need a straight-through connection to the internal port.
Edit your generated
fly.toml, removing both
[[services.ports]] entries for ports 80 and 443 and replacing them with a single entry:
[[services.ports]] handlers =  port = "10000"
This will direct external traffic on port 10000 to internal port 6379. Save the file for now.
Our script takes a password from an environment variable to secure Redis. We need to set that now using the
fly secrets command. This encrypts the value so it can't leak out; the only time it is decoded is into the Fly application as an environment variable.
flyctl secrets set REDIS_PASSWORD=<a password>
And of course, remember that password because you won't be able to get it back.
The last step is to create a disk volume for Redis to save its state on. Then the Redis can be restarted without losing data. For Fly apps, the volume needs to be in the same region as the app. We saw that region when we initialized the app; here it's
ord. We'll give the volume the name
flyctl volumes create redis_server --region ord
Name: redis_server Region: ord Size GB: 10 Created at: 02 Nov 20 19:55 UTC
To connect this volume to the app, pop back to editing fly.toml and add:
[[mounts]] source = "redis_server" destination = "/data"
When the app starts, that volume will be mounted on /data.
We're ready to deploy now. Run
fly deploy and the Redis app will be created and launched on the cloud. Once complete you can connect to it using the
redis-cli command or any other redis client. Just remember to use port 10000, not the default port.
- This configuration sets Redis with mostly default settings.
- You can discuss this example on the community.fly.io topic.