Format startup duration in human-readable units.

[youngledo]

Currently, the startup time of Spring Boot applications is displayed in seconds, but this is not human-friendly for applications with exceptionally long startup times.

Times under 60 seconds continue to use decimal seconds (e.g., "3.456 seconds"), while longer durations are displayed in minutes and seconds (e.g., "1 minute 30 seconds") or hours and minutes (e.g., "1 hour 15 minutes"). This makes startup logs more accessible for applications with longer initialization times.

[snicoll]

Thanks for the PR. I am not sure we should do this, I suspect that some automated process out there is parsing the value. I'll flag for team attention to collect more feedback from the team.

[youngledo]

Thanks for the PR. I am not sure we should do this, I suspect that some automated process out there is parsing the value. I'll flag for team attention to collect more feedback from the team.

Thanks for the feedback! I completely understand the concern about backward compatibility with existing log parsing tools.

I've updated the PR to address this by introducing a configuration option instead of changing the default behavior:

New approach:

• Added a new property spring.main.log-startup-time-format with two values:
  • decimal (default): Keeps the existing format (e.g., "3.456 seconds")
  • human-readable: Uses the new format (e.g., "1 minute 30 seconds")

Key benefits:

• Zero breaking changes: Defaults to the existing decimal format, so all existing log parsers and automation tools continue to work
• Opt-in: Users who prefer human-readable formats can explicitly enable it via configuration
• Backward compatible: The change is purely additive

This way, users who have long-running applications can opt into more readable startup logs without affecting anyone else. The configuration follows the same naming convention as "spring.main.log-startup-info".

[snicoll]

@youngledo please stop. There's no need to change anything until we've had a chance to discuss the merit of the proposal.

[youngledo]

Okay, I won't make any changes for now.

[philwebb]

I often use those number when comparing startup times so I prefer the consistency that the simple seconds figure gives. My vote is to leave things as they are. I also personally don't think the complexity of an additional property is worth the benefit.

[vpavic]

Perhaps ISO 8601 duration format could be considered here? That should be easier to grasp than the current format (PT14M48.643S vs 888.643 seconds), is more parser friendly, and obviously standards based.