Improve upgradeOrder behavior more intuitive and safer

[Jeffwan]

Pull Request Description

1. update the default behavior of upgradeOrder
2. Add integration test into roleset_test.go

follow up PR of #1432

This makes the system much more intuitive and safer - critical components get explicit low order numbers (1,2,3) and upgrade first, while less critical components can be left unspecified and naturally upgrade last.

Behavior:

Before (Confusing):
router(nil=0), prefill(1), decode(2) → [router, prefill, decode]

After (Intuitive):
router(nil=0), prefill(1), decode(2) → [prefill, decode, router]

Related Issues

Resolves: #[Insert issue number(s)]

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[gemini-code-assist]

Summary of Changes

Hello @Jeffwan, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request refines the upgradeOrder behavior for roles within the orchestration system, making the upgrade sequence more predictable and safer. The primary goal is to ensure that roles without a specified upgrade order are processed last, allowing critical, explicitly ordered components to stabilize first. This change is accompanied by robust testing to guarantee the new logic functions as intended.

Highlights

• UpgradeOrder Field Behavior Change: The UpgradeOrder field in RoleSpec has been updated. Previously, a nil value defaulted to 0, implying an early upgrade. Now, nil signifies that the role should be upgraded after all roles with explicitly defined UpgradeOrder values. The minimum valid UpgradeOrder value has also been changed from 0 to 1.
• Improved Upgrade Order Sorting Logic: The internal sorting mechanism for roles during upgrades has been refactored to correctly implement the new UpgradeOrder behavior. Roles with explicit order values are now consistently prioritized over roles where UpgradeOrder is nil.
• Comprehensive Integration Tests for Upgrade Order: Extensive integration tests have been added to roleset_test.go to validate the new UpgradeOrder behavior. These tests cover scenarios including explicit ordering, roles with the same order, and roles with nil order (ensuring they upgrade last), significantly improving the robustness of the upgrade process.

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[gemini-code-assist]

Code Review

This pull request improves the upgradeOrder behavior to be more intuitive, ensuring roles without an explicit order are upgraded last. The changes to the API, sorting logic, and logging are well-implemented. The addition of comprehensive integration tests is a significant improvement to the codebase. I have a few suggestions to enhance code maintainability and strengthen the tests.

[Jeffwan]

/cc @omerap12 I changed the upgradeOrder behavior a little bit, please take a look. /cc @googs1025

[omerap12]

/lgtm

[omerap12]

Since we didn't make a release with #1432 I guess we don't need to have a migration path for roles with order=0 right?

[Jeffwan]

@omerap12 yes. that's true. The main branch is subject to change, so migration plans are only necessary once the change is part of a tagged release.

[omerap12]

@omerap12 yes. that's true. The main branch is subject to change, so migration plans are only necessary once the change is part of a tagged release.

Yeah, just wanted to make sure. Sounds good.