Reconfigure Events

A Reconfigure is when Pico receives a commit in the Configuration Repository and configures itself again at runtime.

During a reconfigure, no new events are processed. Though, configuration does not take very long so it's unlikely any events will be received anyway.

The Process

When config is updated, Pico will first execute the configuration in the configuration engine to validate it and build a new config object.

If the validation fails for any reason, Pico logs an error and stops here. The original configuration remains in-place and its up to you to fix the issues and push new config. There's no need to ever restart Pico in this situation, simply analyse the error, resolve it and push again - Pico will keep trying new commits.

If the validation succeeds, Pico then runs a differential algorithm against the current config and the new config. It will build a list of newly added targets and targets that have been removed.

Now it has those two lists, it will:

  1. Shut down all removed targets using their down commands (if present)
  2. Stand up all added targets using their up commands

Any failures are logged but do not stop the process. A failure at this point is a failure in the target, not Pico itself, so there's no reason to stop and prevent other targets from being executed successfully.

The new config is then committed into Pico's internal state and Pico returns to waiting for:

  1. Configuration repository commits
  2. Target repository commits

And the cycle begins again, as soon as the configuration repository is updated.

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