Main line
Main is the furthest train that has cleared every signal. Many trains run ahead at once, each assuming the one in front passes.
2,140
changes landed in the last hour
9
trains in flight
6
speculation depth
4min 10s
median from attempt-pass to main
0
broken mains in 30 days
Trains ahead of main
One carriage per change, first five shown. Select a train for its detail.
clearedrunningfailedwaitinghalted by failure upstream
B build · U unit · P property · I integration · C canary
Sidings
| Change | Reason | Notified | Auto-retry |
|---|
Landed per 10 minutes
Why this is different
- Main is a position, not a queue. It is the furthest train that has cleared all signals. Nobody presses merge, and nobody waits their turn behind a green tick.
- GitHub today. A merge queue tests a small group, then the next. A red check ejects the author, who goes to the back of the line.
- What breaks at 100,000 agents. At 18,000 changes a day and 20 minutes of CI each, landing one at a time would need 250 days of CI for every day of work. Batches have to run side by side, ahead of main.
- Failure is local. A train with one bad change would sink 63 good ones. Signalbox bisects it automatically, sidelines the culprit with a reason, and re-couples the rest.
- The human sets the rules of the line. The signaller chooses speculation depth and priority. Depth 6 means a failure wastes at most six trains of work.