Restart miren.service after register instead of warning

[phinze]

The warning at the end of miren server register ("you must now restart the miren server") was the bug, but the fix had a couple of layers. The warning fires at the end of every Register call, including from inside miren install, which then turns around and starts the systemd unit itself a few lines later. So during install it's pure noise. During a standalone re-register against a live cluster it's at least correct, but easy to miss in all the other registration output.

I went down the rabbit hole of "could register just be online and not need a restart at all" first. Short version: the cloud authenticator gets wired into RPC server options at construction time with no swap path, plus the build and deployment servers read DNSHostname by value at startup. So it's a real refactor across the auth chain to make any of it dynamic. Maybe worth it someday, but registration is a once-a-quarter operation and the surface area is large.

What we landed on instead: detect a running systemd miren.service and restart it ourselves. Fresh installs (systemd or docker) hit the "unit isn't active yet" branch and stay quiet, since install handles the lifecycle a few lines later anyway. Standalone re-register against a live cluster gets an auto-restart plus a "Restarted miren.service" info line. The one case it still doesn't handle is day-2 re-register on a docker install, but docker is the demo path so it pretty much never happens. Left it.

Closes MIR-1155

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• cli/commands/commands_linux.go
• cli/commands/server_register.go

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• cli/commands/server_register.go

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📝 Walkthrough

Walkthrough

The Register command in the server registration flow now automatically restarts the local miren.service using systemctl after successfully saving an approved registration. A new helper function restartMirenServiceIfActive encapsulates the systemd detection logic, verifying that systemctl is available and the service is currently active before attempting restart. The prior behavior that required users to manually restart the server is removed, with appropriate warning and info logs emitted for various outcomes.

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Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@cli/commands/server_register.go`:
- Line 205: The resumed-pending-registration success branch returns early
without restarting the service, so call restartMirenServiceIfActive(ctx) in that
branch (the code path that handles resuming an existing pending registration and
currently returns before the fresh-registration restart call) — either insert
restartMirenServiceIfActive(ctx) immediately before the early return in the
resume/approve-pending branch or refactor both success paths to use a single
post-success handler that invokes restartMirenServiceIfActive(ctx) so the
restart runs for both fresh and resumed registrations.

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• cli/commands/server_register.go

[evanphx]

We call Register directly from Install as we're doing the install, so I'm worried that a restart here will cause unnecessary churn while the system is trying to come up for the first time.

[evanphx]

Oops, missed the check. is-active being load berring for a proper install feels... weird but fine.

[phinze]

Ya fair point, reworked it so we don't rely on is-active for the install case.