parallel deploy in cluster after splitting it's machines to make sure if something go wrong, there will be a running instances in some servers

publish.sh

#!/usr/bin/env bash

# should have your public key added in every machine server
user=deploybot

servers=(127.18.34.122 127.18.34.123 127.18.34.124 127.18.34.125 127.18.34.126 127.18.34.127 127.18.34.128 127.18.34.129 127.18.34.130)
count=${#servers[@]}

deploy(){
  cluster=("$@")

  echo deploying to cluster ${cluster[@]}

  # run deploy in parallel for every machine in the cluster
  for server in "${cluster[@]}"; do
    (ssh $user@${server} "DEPLOY_COMMAND") &
  done
  wait

}

#split to two cluster
half=$((count / 2))
a_cluster=("${servers[@]:0:$half}")
b_cluster=("${servers[@]:$half}")

# deploy to first cluster then second one
# if deployment failed in first cluster, second one will not be updated, to make sure nothing is broken
deploy "${a_cluster[@]}" && deploy "${b_cluster[@]}"