A bash script for health checking a PostgreSQL. See the start of the script for instructions in how to run it.

health_checking_db.sh

#!/usr/bin/env bash

# How to run:
# 1) `chmod +x health_checking_db.sh`
# 2) `./health_checking_db.sh --password=123 --user=my_user --db_name=my_db --port=5432 --host=localhost --timeout=60`
# Notes for mac:
# Install libpq for psql (https://stackoverflow.com/a/49689589/1651296):
#   `brew install libpq`
#   `export PATH=$PATH:/usr/local/Cellar/libpq/11.1/bin`

# Define a timestamp function
timestamp() {
    date +"%s"
}

# Define a date function
dateString() {
    date +"%T"
}

startTs=$(timestamp)
echo "started at $(dateString) ($(timestamp))"

for i in "$@"
do
case ${i} in
    --password=*)
    password="${i#*=}"
    ;;
    --user=*)
    user="${i#*=}"
    ;;
    --db_name=*)
    db_name="${i#*=}"
    ;;
    --port=*)
    port="${i#*=}"
    ;;
    --host=*)
    host="${i#*=}"
    ;;
    --timeout=*)
    timeout="${i#*=}"
    ;;
    *)
    echo "Unknown option ${i}"
    echo "Ended at $(dateString) ($(timestamp)) (duration: $(($(timestamp)-${startTs})) seconds)"
    exit -1
    ;;
esac
done

if [[ -z "${password}" ]]; then
echo "password is missing, set it as environment variable or pass it as argument ('./health_checking_db.sh --password=123 --user=my_user --db_name=my_db --port=5432 --host=localhost --timeout=60' or 'export password=123')"
echo "Ended at $(dateString) ($(timestamp)) (duration: $(($(timestamp)-${startTs})) seconds)"
exit -1
fi

if [[ -z "${user}" ]]; then
echo "user is missing, set it as environment variable or pass it as argument ('./health_checking_db.sh --password=123 --user=my_user --db_name=my_db --port=5432 --host=localhost --timeout=60' or 'export user=my_user')"
echo "Ended at $(dateString) ($(timestamp)) (duration: $(($(timestamp)-${startTs})) seconds)"
exit -1
fi

if [[ -z "${db_name}" ]]; then
echo "db_name is missing, set it as environment variable or pass it as argument ('./health_checking_db.sh --password=123 --user=my_user --db_name=my_db --port=5432 --host=localhost --timeout=60' or 'export db_name=my_db')"
echo "Ended at $(dateString) ($(timestamp)) (duration: $(($(timestamp)-${startTs})) seconds)"
exit -1
fi

if [[ -z "${port}" ]]; then
port=5432
echo "port is missing, using default '${port}'. You can set it as environment variable or pass it as argument ('./health_checking_db.sh --password=123 --user=my_user --db_name=my_db --port=5432 --host=localhost --timeout=60' or 'export port=${port}')"
fi

if [[ -z "${host}" ]]; then
host="localhost"
echo "host is missing, using default '${host}'. You can set it as environment variable or pass it as argument ('./health_checking_db.sh --password=123 --user=my_user --db_name=my_db --port=5432 --host=localhost --timeout=60' or 'export host=${host}')"
fi

if [[ -z "${timeout}" ]]; then
timeout=60
echo "timeout is missing, using default '${timeout}' seconds. You can set it as environment variable or pass it as argument ('./health_checking_db.sh --password=123 --user=my_user --db_name=my_db --port=5432 --host=localhost --timeout=60' or 'export timeout=${timeout}')"
fi

echo "Health checking for db: '${db_name}', with host: '${host}:${port}', with timeout: '${timeout}' seconds."

sleepTime=0  # do not sleep the first time we call the url

while :
do
    # check if we exceeded the timeout
    totalTimeSpent=$(($(timestamp)-${startTs}))
    if [[ "$totalTimeSpent" -ge "$timeout" ]]; then
    echo "Timeout Error! Didn't receive a success in ${timeout} seconds."
    exit -1
    fi

    # check if the db is created, a combination of:
    # https://stackoverflow.com/a/17757560/1651296
    # https://stackoverflow.com/a/6405296/1651296
    # https://stackoverflow.com/a/15101962/1651296
    # https://www.postgresql.org/docs/current/libpq-envars.html
    if [[ "$(PGPASSWORD=${password} PGHOST=${host} PGPORT=${port} PGUSER=${user} PGDATABASE=${db_name} psql -tAc "SELECT 1 FROM pg_database WHERE datname='${db_name}'" )" = '1' ]]
    then
        echo "Success!"
        exit 0
    fi

    echo "Waiting for result"

    sleep ${sleepTime}
    sleepTime=1  # before calling the url next time sleep for 1 second
done