Count ECS tasks per AZ for a service on a cluster

tasks-per-az.sh

#!/bin/bash    
  
#
# Ouptuts the number of tasks running per AZ for a given service on a given ECS cluster
#

#
# Boilerplate to setup a temp dir since we save some files for intermediate processing
#
set -e -o pipefail

# the directory of the script
DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"

# the temp directory used, within $DIR
# omit the -p parameter to create a temporal directory in the default location
WORK_DIR=$(mktemp -d)

# check if tmp dir was created
if [[ ! "$WORK_DIR" || ! -d "$WORK_DIR" ]]; then
  echo "Could not create temp dir"
  exit 1
fi

# deletes the temp directory
function cleanup {
  rm -rf "$WORK_DIR"
  #echo "Deleted temp working directory $WORK_DIR"
}

# register the cleanup function to be called on the EXIT signal
trap cleanup EXIT
#
# End setup
#

#
# Begin script body
#
CLUSTER=ecs-cluster-name
SERVICE=ecs-service-name

aws ecs list-tasks --cluster $CLUSTER --service-name $SERVICE > tasks.json

aws ecs describe-tasks \
    --cluster $CLUSTER \
    --tasks $(cat tasks.json | jq -r '.taskArns | join(" ")') \
    --query 'tasks[].containerInstanceArn' \
> container-instances.json

aws ecs describe-container-instances \
    --cluster $CLUSTER \
    --container-instances $(cat container-instances.json | jq -r '. | join(" ")') \
    --query 'containerInstances[].attributes[?name==`ecs.availability-zone`]' \
> container-instance-azs.json

cat container-instance-azs.json | jq -r '.[][]| .value ' | sort | uniq -c