In short, a programmable cloud delivery network (CDN) aka front-end like Fly.io is an API by which to configure the logical edge of an application stack. Fly.io also provides an intuitive web UI which simplifies common administrative operations.
- high availability for a service endpoint (this is automatic);
- requesting, issuing, binding, and renewing a free TLS server certificate (just verify a domain name);
- injecting business logic and automation at the application edge e.g. analytics, policies, authentication, caching, redirects, lambda functions, etc... (just click to enable middleware); and
- allocating workloads to multiple upstreams (backend capacity pools e.g. GCE, ECS, EC2).
Example of a multi-cloud backend fronted by Fly.io
For one project I created a Fly.io "site" to front an application served up by Kubernetes in Google Compute Engine (GCE) and Elastic Container Service (ECS) simultaneously. Such a multi-cloud architecture is typically possible with any CDN, but here's an overview of the steps to do this with Fly.io.
docker pushto upload my custom Docker image to the Elastic Container Registry (ECR)
- configure the Kubernetes cluster to source that container image by registry address, name:tag, and publish the service port on a load balancer
- configure AWS's ECS Fargate to source the image by name:tag (requires hosting the container image in ECR), and publish the service port on an Elastic Load Balancer (ELB)
- create the Fly.io site with a backend of the Kubernetes load balancer address:port and ELB address:port
A note about TLS (SSL): It's a great idea to require TLS everywhere. This gives greater assurance of data integrity even when confidentiality is a non-issue. Both GCE Kubernetes LBs and ELBs can issue and bind a free TLS server certificate. There's no need to request a certificate common name (CN) or subject alternative name (SAN) matching the domain name your clients/customers will "see". This is because the frontend provided by Fly.io will bind that familiar domain name when you verify the DNS hostname. The CN+SAN in the backend load balancers' server certificates are arbitrary and simply need to match the domain name generated by that platform for the particular service address e.g. example-service-2045107736.us-east-1.elb.amazonaws.com.
Example of a personal web site without hosting expenses
I came across Fly.io by way of an email invitation for a free trial and have combined this with the Keybase Filesystem and the Pelican static HTML generator (described in About page) to create this blog site which is highly secure, performant, highly available, and (for now) completely free of operational expenses!