Monster Market is moving to a fleet. The install script is ~/app.sh (each server needs about a minute to start and then answers /health), and the next release is ~/v2.sh.

1. A load balancer market-alb in us-east-1a and us-east-1b, with its own security group open on port 80, forwarding to a target group market-tg that checks /health. The servers accept port 80 from the load balancer only.

2. A launch template market-lt from app.sh, and an Auto Scaling group market-asg that keeps three instances from it in both zones, registered in market-tg and replaced when their checks fail.

3. Game day, once all three are healthy. Take a zone down with the market's chaos tool, and wait until the group runs three healthy instances again:

   sh

   copy

   chaos zone-down us-east-1a

   Then bring the zone back with chaos zone-up us-east-1a, and wait until the group spreads over both zones again.

4. Roll v2.sh out to every instance, never with fewer than three healthy.

From the first time the shop answers, an outside check fetches it every 5 seconds. No more than 4 of those fetches may fail in all, and never for more than 30 seconds in a row. chaos status shows the count so far; resetting the lab starts it again. How quickly the load balancer notices a server is gone is yours to tune.