Scale to zero for Node.js applications

[daansk44]

Hi everyone,

Some time ago I noticed that there is a nice article about a Minecraft server that has the possibility to scale to zero.

Now we have quite a powerful node.js application that now also runs on fly.io. However, since we are still in the test phase, it is called 1 to 5 times per hour per day.

However, when it is running, we need 1 to 2 gigs of ram to run it properly. However, it is a waste of energy to keep it running continuously.

Is it possible to scale to zero for a Node.js application on Fly.io? The application uses express as web server?

[rubys]

There are two requirements for scaling to zero:

• Your app must be on the machines platform.
• Your app must exit with rc of 0 when idle.

You chose the machines platform via specifying --machines on the fly apps create command. You once created you can use your same Dockerfile, fly.toml, etc. Machines is still under active development, but should be fine for tests.

[ignoramous]

@rubys

Your app must exit with rc of 0 when idle.

Any clarity on what a restart_policy is and what they mean for Machines exiting with various exit-codes, if set?

How do I change the restart policy for Machines?

Most our services rely on health checks. Any timeline for these for Machines? If there aren’t health-checks for Machines, what does the restart-policy act on? Does it monitor the exit code to apply restart-policies? a. Does no mean, a new vm is started on next request? b. Does always mean, even if it exits with 0, the main process is restarted inside the existing vm? c. Does on-failure mean, only on non-zero exit codes, the main process is restarted in the existing vm? What does the defa…

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@daansk44

Now we have quite a powerful node.js application that now also runs on fly.io. However, since we are still in the test phase, it is called 1 to 5 times per hour per day.

We run a Node app on machines: Here’s some relevant code bits.

[daansk44]

@rubys

rc of 0

You mean doing this?

let exitCode = 1;
process.exit(exitCode)

[ignoramous]

@daansk44

You mean doing this?

process.exit(0) is what we do.