cloud: optional AZ for spot launches

scripts/cloud/trial.sh

@@ -17,6 +17,7 @@ TYPE=${TYPE:-m7g.4xlarge}
 MAX_PRICE=${MAX_PRICE:-0.30}        # USD/hour spot cap (on-demand is 0.6528)
 MAX_MINUTES=${MAX_MINUTES:-360}     # hard cap: 6 hours
 DISK_GB=${DISK_GB:-250}
+AZ=${AZ:-}                          # e.g. us-east-1b when another zone's spot price is above MAX_PRICE
 DISK_MBPS=${DISK_MBPS:-125}         # gp3 throughput (125 = free baseline; each extra MB/s ~ $0.00005/h)
 DISK_IOPS=${DISK_IOPS:-3000}        # gp3 IOPS (3000 = free baseline)
 BUDGET_USD=${BUDGET_USD:-10}
@@ -73,7 +74,7 @@ launch)
   echo "-> task: $TASK"
   echo "-> launching $TYPE spot (cap \$$MAX_PRICE/h, hard limit ${MAX_MINUTES} min, ${DISK_GB} GB disk deleted on exit)"
   ID=$($AWS ec2 run-instances --image-id "$AMI" --instance-type "$TYPE" --count 1 \
-    --iam-instance-profile Name=$ROLE \
+    --iam-instance-profile Name=$ROLE ${AZ:+--placement AvailabilityZone=$AZ} \
     --instance-initiated-shutdown-behavior terminate \
     --instance-market-options "MarketType=spot,SpotOptions={MaxPrice=$MAX_PRICE,SpotInstanceType=one-time,InstanceInterruptionBehavior=terminate}" \
     --block-device-mappings "DeviceName=/dev/sda1,Ebs={VolumeSize=$DISK_GB,VolumeType=gp3,Throughput=$DISK_MBPS,Iops=$DISK_IOPS,DeleteOnTermination=true}" \