How to run db migration script in a kubernetes pod from bash? - bash

Question

I would like to run database migration scripts in Ubuntu pod automatically.
How I am doing this manually:
$ kubectl run -i --tty ubuntu --image=ubuntu:focal -- bash
$ apt install -y postgresql-client
$ psql "hostaddr=addr port=5432 user=username password=pass dbname=dbname"
COPY persons(first_name, last_name, dob, email)
FROM './persons.csv'
DELIMITER ','
CSV HEADER;
$ exit
I would like to create a bash script for this purposes to run locally. Could you please advise how to script it? First command connects to a remote bash session, and I am not able to execute other commands. Definitely doing something wrong.
Thank you.

Answer 1

Use here documents.
#!/bin/bash
kubectl run -i --tty ubuntu --image=ubuntu:focal -- bash <<EOF
apt install -y postgresql-client
psql "hostaddr=addr port=5432 user=username password=pass dbname=dbname" <<EOF2
COPY persons(first_name, last_name, dob, email)
FROM './persons.csv'
DELIMITER ','
CSV HEADER;
EOF2
EOF

Answer 2

Let's assume we have a command that is supposed to be run to execute some SQL query on a postgresql server in a Kubernetes cluster:
export pgcmd="PGPASSWORD=pass1234 psql -U username -d mydatabase -h addr -p port -c \"COPY persons(first_name, last_name, dob, email) FROM './persons.csv' DELIMITER ',' CSV HEADER;\" "
or by using URL syntax
export pgcmd="psql postgresql://username:pass#addr:5432/mydatabase -c \"COPY persons(first_name, last_name, dob, email) FROM './persons.csv' DELIMITER ',' CSV HEADER;\" "
Actually, it's more convenient to use official postgres docker image instead of installing postgresql client on Ubuntu image:
(if I use the same image as used to spin up the posgresql server, I can save some time on pulling image from the repository)
kubectl run -it --rm pgclient --image=postgres -- $pgcmd
Alternatively you can run the command using posgresql pod itself
kubectl exec -it posgresql-server-pod-name -- $pgcmd
or proxy connection to the postgresql server and execute the command there
kubectl port-forward posgresql-server-pod-name 8888:5432 &
#or we can use parent object to connect
#kubectl port-forward deployment/posgresql-server-deploy-name 8888:5432 &
# save ID of the background process
proxyid=$!
# run postgres command locally
$pgcmd
# switch off port forwarding and cleanup environment variables
unset PGPASSWORD
kill $proxyid && unset proxyid