Create/update/delete cloudformation stacks with events tailing

deploy_stack.sh

set -o pipefail

_exit_error() {
  message=$1
  code=$2
  echo "$message" >&2
  exit $code
}

_exit_ok() {
  message=$1
  echo "$message"
  exit 0
}

get-stack-state() {
  local stack_name=$1
  local region=$2
  local stack_state
  stack_state=$(aws cloudformation describe-stacks --region $region \
                                                   --stack-name $stack_name \
                                                   --query "Stacks[0].StackStatus" \
                                                   --output text 2>&1)
  retcode="$?"
  if <<<"${stack_state}" grep -q "does not exist"; then
    _exit_ok DOES_NOT_EXIST
  fi
  if [ $retcode -ne 0 ]; then
    _exit_error "$stack_state" $retcode
  fi
  _exit_ok "$stack_state"
}

get-stack-action() {
  local stack_state=$1
  local stack_action
  case $stack_state in
    *_IN_PROGRESS)  # busy
                    _exit_error "Stack is currently in $stack_state state and cannot be updated" 127
                    ;;
    *_FAILED)       # errored
                    _exit_error "Stack is currently in $stack_state state and cannot be updated" 127
                    ;;
    ROLLBACK_COMPLETE)     # ok
                    stack_action="delete-then-create"
                    ;;
    *_COMPLETE)     # ok
                    stack_action="update"
                    ;;
    DOES_NOT_EXIST) # nope
                    stack_action="create"
                    ;;
    *)              # unknown
                    ;;
  esac
  echo "$stack_action"
}

upsert-stack() {
  local stack_required_action=$1
  local stack_name=$2
  local stack_template=$3
  local region=$4
  local upsert_result
  local retcode
  echo "Attempting to $stack_required_action stack: $stack_name..." >&2
  upsert_result=$(aws cloudformation ${stack_required_action}-stack --region        $region \
                                                                    --capabilities  CAPABILITY_IAM CAPABILITY_NAMED_IAM \
                                                                    --stack-name    $stack_name \
                                                                    --template-body file://./cloudformation/$stack_template.yml \
                                                                    --parameters    file://./cloudformation/.tmp/cloudformation_parameters-$stack_template.json \
                                                                    --query         StackId \
                                                                    --output        text 2>&1)
  retcode="$?"
  if <<<"${upsert_result}" grep -q "No updates are to be performed"; then
    _exit_ok "No updates are to be performed"
  fi
  if [ $retcode -ne 0 ]; then
    _exit_error "$upsert_result" $retcode
  fi
  echo "$upsert_result"
}

tail_stack() {
  local stack_name=$1
  local region=$2
  local current
  local final_line
  local output
  local output_result
  local previous
  local stack_events
  local now=$(date -u +"%Y-%m-%dT%H:%M:%SZ")
  local headings="| Time         | Resource                       | Status                         | Message                                                      |"
  local markline="+--------------+--------------------------------+--------------------------------+--------------------------------------------------------------+"
  local header="$markline\n$headings\n$markline\n"
  local colour_reset='\033[0m'
  local colour_red='\033[31m'
  local colour_green='\033[32m'
  local colour_yellow='\033[33m'
  local colour_blue='\033[34m'
  local colour_magenta='\033[35m'
  local colour_cyan='\033[36m'
  local colour_white='\033[97m'

  while true; do
    stack_events=$(aws cloudformation describe-stack-events --region $region \
                                                            --stack-name $stack_name \
                                                            --output text \
                                                            --query "sort_by(StackEvents, &Timestamp)[?Timestamp>='$now'].[
                                                                Timestamp,
                                                                LogicalResourceId,
                                                                ResourceStatus,
                                                                ResourceStatusReason,
                                                                ResourceType
                                                              ]" 2>&1)
    retcode="$?"
    echo "$stack_events" | egrep -q "does not exist" && break
    if [ $retcode -ne 0 ]; then
      _exit_error "$stack_events" $retcode
    fi
    if [ -z "$stack_events" ]; then
      sleep 1
      continue
    fi
    stack_events_table=$(
      while IFS=$'\t' read timestamp resource status message rtype; do
        # ResourceType (rtype) not used, included for completeness
        printf "| %b%-12s%b | %b%-30s%b | %b%-30s%b | %b%-60s%b |\n" \
               "$colour_green" "${timestamp:11:8} UTC"          "$colour_reset" \
               "$colour_red"   "$(echo $resource | awk -v len=30 '{ if(length($0)>len) print "…" substr($0,length($0)-len+2,length($0)); else print;}')" "$colour_reset" \
               "$colour_cyan"  "$(echo $status   | awk -v len=30 '{ if(length($0)>len) print "…" substr($0,length($0)-len+2,length($0)); else print;}')" "$colour_reset" \
               "$colour_blue"  "$(echo $message  | awk -v len=60 '{ if(length($0)>len) print "…" substr($0,length($0)-len+2,length($0)); else print;}')" "$colour_reset"
      done <<< "$stack_events"
    )
    current=$(echo -e "$header$stack_events_table")
    if [ -z "$previous" ]; then
      echo "$current"
    elif [ "$current" != "$previous" ]; then
      comm -13 <(echo "$previous") <(echo "$current")
    fi
    previous="$current"
    stack_state=$(aws cloudformation describe-stacks --region $region \
                                                     --stack-name $stack_name \
                                                     --query "Stacks[0].StackStatus" \
                                                     --output text 2>&1)
    retcode="$?"
    echo "$stack_state" | egrep -q ".*_(COMPLETE|FAILED)$" && break
    [ $retcode -ne 0 ] && break
    sleep 1
  done
  echo $markline
}

deploy_stack() {
  local application=$1
  local environment=$2
  local stack_template=$3
  local region=$4
  local stack_name
  local stack_required_action
  stack_name=$(echo "$application-$environment-$stack_template" | tr '_' '-')

  echo "Checking state of stack: $stack_name..."
  stack_state=$(get-stack-state $stack_name $region) || exit $?
  stack_action=$(get-stack-action $stack_state) || exit $?
  if [[ $stack_action == "delete-then-create" ]]; then
    echo "Stack exists in non-updatable state. Deleting..." >&2
    drop_stack $application $environment $stack_template $region
    stack_action="create"
  fi
  upsert_result=$(upsert-stack $stack_action $stack_name $stack_template $region) || exit $?
  if <<<"${upsert_result}" grep -q "No updates are to be performed"; then
    _exit_ok "$upsert_result"
  fi
  echo "Stack with id $upsert_result is being ${stack_action}d"
  tail_stack $stack_name $region
}

delete-stack() {
  local stack_name=$1
  local region=$2
  local delete_result
  local retcode
  echo "Attempting to delete stack: $stack_name..." >&2
  delete_result=$(aws cloudformation delete-stack --stack-name $stack_name --region $region 2>&1)
  retcode="$?"
  if [ $retcode -ne 0 ]; then
    _exit_error "$delete_result" $retcode
  fi
  # delete_result is empty if there is no error, so no return here
}

drop_stack() {
  local environment=$1
  local application=$2
  local stack_template=$3
  local region=$4
  local stack_name
  local stack_required_action
  stack_name=$(echo "$environment-$application-$stack_template" | tr '_' '-')
  echo "Checking state of stack: $stack_name..."
  stack_state=$(get-stack-state $stack_name $region) || exit $?
  if <<<"${stack_state}" egrep -q "DOES_NOT_EXIST"; then
    _exit_error "The stack $stack_name does not exist"
  fi
  delete_result=$(delete-stack $stack_name $region) || exit $?
  tail_stack $stack_name $region
}

Call deploy_stack to create/update a stack
Call drop_stack to delete a stack