Improved computation of items/minute and time remaining

[dpp]

💻 Description of Change(s) (w/ context)

Improved computation of items/minute and time remaining

🧠 Rationale Behind Change(s)

Improve observability

📝 Test Plan

passes tests

📜 Documentation

💣 Quality Control

(All items must be checked before a PR is merged)
Did you…

• Mention an issue number in the PR title?
• Update the version # in the build file?
• Create new and/or update relevant existing tests?
• Create or update relevant documentation and/or diagrams?
• Comment your code?
• Fix any stray verbose logging (removing, or moving to debug / trace level)?

Before Merging…

• Make sure the Quality Control boxes are all ticked
• Make sure any open comments or conversations on the PR are resolved

[aredridel]

Makes sense, and TIL @volatile. I don't think there's any interesting data race if it were omitted but it's correct.

[dpp]

@volatile for a Boolean may not be a huge issue... but we are all running multi-processor boxes with non-uniform memory access. It's likely the the Boolean may be seen differently between CPUs depending on cache where @volatile ensures cache coherence. But the cost of this one being wrong is quite low.

@volatile for the Instant is important. Depending on processor type and memory access patterns, 64 bit pointer writes may be atomic and they may be broken into 2 32 bit writes. Ensuring the atomic write for the Instant reference is necessary.