How to wait in bash script until AWS instance creation is complete - bash

Question

I'm using a bash script to create an AWS instance via CLI and a cloudformation template. I want my script to wait until the instance creation is complete before I move on in my script. Right now, I'm using a while loop to "describe-stacks" every 5 seconds, and breaking out of the loop when the status = "CREATE_COMPLETE" or some failure status. Does anyone know of a more elegant way to do this?
stackStatus="CREATE_IN_PROGRESS"
while [[ 1 ]]; do
echo "${AWS_CLI_PATH}" cloudformation describe-stacks --region "${CfnStackRegion}" --stack-name "${CfnStackName}"
response=$("${AWS_CLI_PATH}" cloudformation describe-stacks --region "${CfnStackRegion}" --stack-name "${CfnStackName}" 2>&1)
responseOrig="$response"
response=$(echo "$response" | tr '\n' ' ' | tr -s " " | sed -e 's/^ *//' -e 's/ *$//')
if [[ "$response" != *"StackStatus"* ]]
then
echo "Error occurred creating AWS CloudFormation stack. Error:"
echo " $responseOrig"
exit -1
fi
stackStatus=$(echo $response | sed -e 's/^.*"StackStatus"[ ]*:[ ]*"//' -e 's/".*//')
echo " StackStatus: $stackStatus"
if [[ "$stackStatus" == "ROLLBACK_IN_PROGRESS" ]] || [[ "$stackStatus" == "ROLLBACK_COMPLETE" ]] || [[ "$stackStatus" == "DELETE_IN_PROGRESS" ]] || [[ "$stackStatus" == "DELETE_COMPLETE" ]]; then
echo "Error occurred creating AWS CloudFormation stack and returned status code ROLLBACK_IN_PROGRESS. Details:"
echo "$responseOrig"
exit -1
elif [[ "$stackStatus" == "CREATE_COMPLETE" ]]; then
break
fi
# Sleep for 5 seconds, if stack creation in progress
sleep 5
done

Answer 1

The aws cli provides a wait subcommand for most of the commands that create resources. For your scenario, you can use the wait subcommand to wait for the stack-create-complete event:
aws cloudformation wait stack-create-complete --stack-name myStackName

Answer 2

That is how I did it. After start of instance I wait for public IP:
INSTANCE_ID="$(aws ec2 run-instances --cli-input-json "${LAUNCH_SPEC}" | jq -r '.Instances[0].InstanceId')"
echo "Instance id ${INSTANCE_ID}"
while true; do
PUBLIC_IP="$(aws ec2 describe-instances --instance-ids ${INSTANCE_ID} | jq -r '.Reservations[0].Instances[0].PublicIpAddress')"
if [[ "${PUBLIC_IP}" =~ ^([0-9]{1,3}\.){3}[0-9]{1,3}$ ]]; then break; fi
sleep 1
echo -n '.'
done
LAUNCH_SPEC defined previously

Answer 3

Ec2-wait-instance-exists seems like what you need:
http://docs.aws.amazon.com/cli/latest/reference/ec2/wait/instance-exists.html

Answer 4

The below is a general "check_status" function. Useful for multiple action such as checking whether stack has been deployed or an EKS cluster is up and whether nodes were added to it.
check_status() {
max_tries="$1"
test_command="$2"
required_value="$3"
error="$4"
ok="false"
for i in `seq 1 $max_tries`; do
return_value=$(eval ${test_command})
if [ "$return_value" == "$required_value" ]; then
ok="true"
break
else
echo -n "."
fi
sleep 5
done
if [ "$ok" == "false" ]; then
printf "\n\e[31mERROR:\e[0m $error\n"
exit 1
fi
}
check_vpc() {
echo "Waiting for stack status..."
vpc_stack_status="aws cloudformation describe-stacks --stack-
name=${vpc_stack_name} --query 'Stacks[0].StackStatus' --output text"
msg="Stack creation failed - giving up"
check_status "100" "$vpc_stack_status" "CREATE_COMPLETE" "$msg"
[[ $? == "0" ]] && echo "VPC stack deployed successfully"
}