Dynamic Config

Whenever a configuration option is used in a “one shot” fashion it could be dynamically fetched instead of requiring a process restart. This would give greater configuration control without restarts as well as provide a central configuration place (no need to update every configuration file on every server).

For example:

  • The timeout for an operation is fixed at the start of each operation …
  • … VS the database server requires a restart to change.

Why delay improving?

  • Needs are yet unkown.
  • Config will likely see large changes.

Potential improvement

  1. Split the configuration object into two static objects:
    • Static configuration options are left in the existing file.
    • Dynamic configuration options are moved to a new file.
  2. Change the dynamic configuration object to have a more dynamic API.
    • Possibly implement some wrapper type that DeRef to the requested type and is loaded when accessed (possibly cache in memory for sanity).
    • Possibly not so the cost/risk of dynamic lookup can be exposed.
    • Consider a dynamic configuration loader that returns a static view on the full dynamic configuration options vs dynamic loading of individual attributes.
    • Keep the stored format decoupled from the exposed interface (mainly the full configuration should be stored and picked from by the API).
    • Provide an official way to update dynamic configuration (replictl).
  3. Update user code, if needed, to use a dynamic fetch API.
  4. At startup, warn if the dynamic config loaded is not the same as the dynamic config file?

Downsides the new solution/idea

  • Extra complexity in the code.
  • Extra deployment complexity (need a configuration store of sorts).
  • Less obvious configuration methods (upload configuration file to store? Changes done with replictl?)