How to attach volume to pod's post start life cycle hook? - openshift

Question

The use case trying out is, way to initialize the postgres database after it starts up. I saw the post start hooks in the openshift pod lifecycle. I can't put the sql statements using here-document or in command line ( Docker command fails due to max length issue ).
So looking a option to save the SQL statements in a file via ConfigMap and attach it to the post container before it starts, so that the psql command can execute it. I couldn't see a way to attach the volume from the DeploymentConfig from the official document. Is there any way I can do it ?
Document I referred - openshift-doc

Answer 1

I found a workaround to pass the long SQL statements to the post life-cycle pods.
Set the SQL statements in the DeploymentConfig ENV variable. These ENV variables are accessible inside the life cycle pods also, so then we can easily do the bellow command
post:
failurePolicy: Abort
execNewPod:
command:
- /bin/bash
- '-c'
- >-
echo $INIT_SQL_STATEMENTS | psql "sslmode=allow
host=postgres user=postgres password=postgres"
containerName: postgres
.....
env:
- name: POSTGRESQL_ADMIN_PASSWORD
value: postgres
- name: INIT_SQL_STATEMENTS
value: >-
create user haridas with encrypted password 'haridas';...

Answer 2

Another option which I've employed in the past is to pass in the sql statements in a parameters file. This will then allow you to more easily configuration manage the sql commands (e.g. check it into git) and declutter your deployment configuration (DC). Here is what I did:
Move your post hook to the DC portion of the template file. Let me
know if you need steps on how to export, modify, and re-import a
template file, but I didn't want to over-complicate this procedure
unnecessarily.
Add a parameter to the template file called SQL_COMMANDS like this:
parameters:
- description: The SQL commands to run.
displayName: SQL commands
name: SQL_COMMANDS
required: true
In the post hook code of the template (DC section) run the SQL_COMMANDS like this:
execNewPod:
command:
- /bin/sh
- -c
- echo "${SQL_COMMANDS}" | psql -h ${DATABASE_SERVICE_NAME} -U ${POSTGRESQL_USER} -d ${POSTGRESQL_DATABASE};
Note the other variables in the command are also passed in as parameters.
Create a parameters file similar to this:
POSTGRESQL_USER=postgres
POSTGRESQL_PASSWORD=somepassword
POSTGRESQL_DATABASE=myDatabase
SQL_COMMANDS="CREATE TABLE Configuration(CONFIGURATION_ID character varying(255)
NOT NULL, description character varying(255)
NOT NULL, key character varying(255) NOT NULL, value text NOT NULL,
PRIMARY KEY (CONFIGURATION_ID) ); INSERT INTO Configuration
(CONFIGURATION_ID, description, key, value) VALUES ('10', ... etc."
Deploy your app using the template and pass in the parameters from the file:
oc new-app <template name> --param-file=ParametersFile.txt