init-snapshot VS flyctl

At CodeSandbox we use Firecracker to run our VMs (more info here: https://codesandbox.io/blog/how-we-clone-a-running-vm-in-2-s...).

To answer the questions:

> what version of the kernel do you use (the github page says 5.10 but isn't that quite old?)

Right, they have tested with 5.10, but it also works with higher kernel versions. Our host currently runs 5.19 and we're planning to upgrade to 6.1 soon. The guest runs 5.15.63, we use a config very similar to the recommended config by FC team (it's in the FC repo). It's important to mention that we had to disable async pagefaulting (a KVM feature) with more modern kernel versions, as VMs could get stuck waiting for an PF resolve.

> What do you use to build the 'micro' images

We created a CLI that creates a rootfs from a Docker image. It pulls the image, creates a container and then extracts the fs from it to an ext4 disk. For the init, we forked the open sourced init from the Fly team (https://github.com/superfly/init-snapshot) and changed/added some functionality.

> How do you keep timesync of you're not using a timesync daemon?

IIRC we expose the time as a PTP device (handled by kvm) and run phc2sys to sync the time in an interval. Firecracker has some documentation on this, where it recommends chrony. It can also be done with vsock, but it would be more manual.

> Handle kernel and app logs without adding an log daemon, and same through vsocks, etc?

The init forwards stdout/stderr of the command it runs to its own stdout, which Firecracker then logs out by itself. A supervisor reads these and writes the logs to files.

Unless they’ve changed things, there is no containerization within the VM a la kata. They run their own custom init inside the VM and use it to start the entry point. https://github.com/superfly/init-snapshot is the source.

Jerome wrote our init in Rust, and, after being cajoled by Josh Triplett, [we released the code (https://github.com/superfly/init-snapshot), which you can go read.

> Fly.io transforms container images into fleets of micro-VMs running around the world on our hardware.

Oh boy!

> None of us have ever worked for Google, let alone as SREs. So we’re going out on a limb

Oh.... boy.

> We spent some time scaling it with Thanos, and Thanos was a lot, as far as ops hassle goes.

You know, they have these companies now, that will collect your metrics for you, so that you don't have to deal with ops hassle.

Holy shit. I see they even wrote their own init... in Rust. Yes, the thing that is normally a shell script, is now a compiled program in a new language, that mostly just runs mkdir(), mount() and ethtool(). (https://github.com/superfly/init-snapshot/blob/public/src/bi...)

Create an account on Fly.io.

You can learn more about fly.io and tigris, we will need to create an account on both platforms for this project regardless. Anyway with the theory out of the way let's get started in the next section as we create our accounts and start building the app.

Fly.io is a platform that helps you run your apps and databases closer to your users all around the world. It takes your app code, packages it up neatly, and puts it on virtual machines that can be quickly started or stopped. This makes your app faster for users and more reliable. Fly.io is easy to use, works well for small projects or personal apps. It's a great way to make sure your app runs smoothly for people no matter where they are.

In this post, we'll start from scratch, running FerretDB locally via Docker, trying out the connection with mongosh and the MongoDB Node.js client, and finally deploy FerretDB to Fly.io for a production ready set up.

2- fly.io

Fly is a cloud platform that focuses on global edge computing. Fly specializes in high-performance hosting and provides a global network of edge locations. Fly is known for its scalability and performance optimizations.

But videototextai.com is built using NextJS + Firebase auth + Firestore and a backend deployed at fly.io . Fly makes it really easy to deploy docker containers and that is IMO the fastest way to develop, you can setup a local setup

Alternatives explored: * northflank: While running the wrk test, requests were taking 3-7 seconds. Couldn't repeat Heroku's phenomenon of "400ms-800ms" during such a load test. * fly.io: Reliability: It’s Not Great * render.com: I remember the time when indiehackers.com was down because of an outage on Render, not sure if it's worth trusting.

For personal/portfolio projects fly.io and render.com both have free tiers that support the major backend frameworks and Postgres at the very least (although I think with Render at least the DB expires and has to be reloaded after a certain amount of time, have not personally tried it).

We must download and install CLI for fly.io. If you use Windows, you can download the installer by this link. Or you can also use PowerShell script as well.