Better fly.toml validation

Fresh Produce
1

We already have the following command for performing app configuration validation: flyctl config validate -c fly.toml

This command performs checks like “does a [[services]] section expose at least one port” or “is the deployment strategy one of the allowed values”, etc.

One thing it doesn’t do, and which seems to fairly often be a source of confusion, is check for any “unrecognised” sections and/or fields.

Sometimes when something isn’t working, you might try popping various bits of config all across your fly.toml in the hopes that one of them does the right thing. Or you might simply have misspelt something and it’s being silently ignored.

Not knowing which field is actually being utilised by the Fly platform leaves your config in a brittle state, because you don’t know what’s important and what isn’t, and the feedback loop for finding out is a full deploy, which is tedious to say the least.

Enter: flyctl config validate --strict

All it’ll do is tell you if there’s config somewhere it shouldn’t be. But that alone might be enough to put you back on track.

Example

fly.toml:

app = "bla"
primary_region = "mia"
console_command = "bin/rails console"

[http_service]
  processes = ["app"]
  internal_port = 3000
  auto_stop_machines = "suspend"
  auto_start_machines = true
  min_machines_running = 1

[http_service.concurrency]
  # `processes` is not a valid field here
  processes = ['app']
  type = "requests"
  soft_limit = 50
  hard_limit = 70

# This should be `[[http_service.machine_checks]]`
[[http_machine.checks]]
  processes = ['app']
  grace_period = "30s"
  image = "curlimages/curl"
  entrypoint = ["/bin/sh", "-c"]
  command = ["curl http://[$FLY_TEST_MACHINE_IP]/up | grep 'background-color: green'"]
  kill_signal = "SIGKILL"
  kill_timeout = "5s"

% fly config validate --strict -c fly.toml
Validating fly.toml
✓ Configuration is valid


Strict validation found unrecognised sections or keys:
  - http_machine
  - http_service.concurrency.processes


Error: strict validation failed
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