Migrating Database Applications

Overview

This topic reviews how to migrate MySQL, PostgreSQL, and MongoDB database applications from OpenShift version 2 (v2) to OpenShift version 3 (v3).

Supported Databases

MySQL

1. Export all databases to a dump file and copy it to a local machine (into the current directory):

   $ rhc ssh <v2_application_name>
   $ mysqldump --skip-lock-tables -h $OPENSHIFT_MYSQL_DB_HOST -P ${OPENSHIFT_MYSQL_DB_PORT:-3306} -u ${OPENSHIFT_MYSQL_DB_USERNAME:-'admin'} \
    --password="$OPENSHIFT_MYSQL_DB_PASSWORD" --all-databases > ~/app-root/data/all.sql
   $ exit

2. Download dbdump to your local machine:

   $ mkdir mysqldumpdir
   $ rhc scp -a <v2_application_name> download mysqldumpdir app-root/data/all.sql

3. Create a v3 mysql-persistent pod from template:

   $ oc new-app mysql-persistent -p \
      MYSQL_USER=<your_V2_mysql_username> -p \
      MYSQL_PASSWORD=<your_v2_mysql_password> -p MYSQL_DATABASE=<your_v2_database_name>

4. Check to see if the pod is ready to use:

   $ oc get pods

5. When the pod is up and running, copy database archive files to your v3 MySQL pod:

   $ oc rsync /local/mysqldumpdir <mysql_pod_name>:/var/lib/mysql/data

6. Restore the database in the v3 running pod:

   $ oc rsh <mysql_pod>
   $ cd /var/lib/mysql/data/mysqldumpdir

   In v3, to restore databases you need to access MySQL as root user.

   In v2, the **$OPENSHIFT_MYSQL_DB_USERNAME** had full privileges on all databases. In v3, you must grant privileges to **$MYSQL_USER** for each database.

   $ mysql -u root
   $ source all.sql

   Grant all privileges on to <your_v2_username>@localhost, then flush privileges.

7. Remove the dump directory from the pod:

   $ cd ../; rm -rf /var/lib/mysql/data/mysqldumpdir

Supported MySQL Environment Variables

PostgreSQL

1. Back up the v2 PostgreSQL database from the gear:

   $ rhc ssh -a <v2-application_name>
   $ mkdir ~/app-root/data/tmp
   $ pg_dump <database_name> | gzip > ~/app-root/data/tmp/<database_name>.gz

2. Extract the backup file back to your local machine:

   $ rhc scp -a <v2_application_name> download <local_dest> app-root/data/tmp/<db-name>.gz
   $ gzip -d <database-name>.gz

   Save the backup file to a separate folder for step 4.

3. Create the PostgreSQL service using the v2 application database name, user name and password to create the new service:

   $ oc new-app postgresql-persistent -p POSTGRESQL_DATABASE=dbname -p
   POSTGRESQL_PASSWORD=password -p POSTGRESQL_USER=username

4. Check to see if the pod is ready to use:

   $ oc get pods

5. When the pod is up and running, sync the backup directory to pod:

   $ oc rsync /local/path/to/dir <postgresql_pod_name>:/var/lib/pgsql/data

6. Remotely access the pod:

   $ oc rsh <pod_name>

7. Restore the database:

   psql dbname < /var/lib/pgsql/data/<database_backup_file>

8. Remove all backup files that are no longer needed:

   $ rm /var/lib/pgsql/data/<database-backup-file>

Supported PostgreSQL Environment Variables

MongoDB

1. Remotely access the v2 application via the ssh command:

   $ rhc ssh <v2_application_name>

2. Run mongodump, specifying a single database with -d <database_name> -c <collections>. Without those options, dump all databases. Each database is dumped in its own directory:

   $ mongodump -h $OPENSHIFT_MONGODB_DB_HOST -o app-root/repo/mydbdump -u 'admin' -p $OPENSHIFT_MONGODB_DB_PASSWORD
   $ cd app-root/repo/mydbdump/<database_name>; tar -cvzf dbname.tar.gz
   $ exit

3. Download dbdump to a local machine in the mongodump directory:

   $ mkdir mongodump
   $ rhc scp -a <v2 appname> download mongodump \
     app-root/repo/mydbdump/<dbname>/dbname.tar.gz

4. Start a MongoDB pod in v3. Because the latest image (3.2.6) does not include mongo-tools, to use mongorestore or mongoimport commands you need to edit the default mongodb-persistent template to specify the image tag that contains the **mongo-tools, “mongodb:2.4”**. For that reason, the following oc get --export command and edit are necessary:

   $ oc get -o json --export template mongodb-persistent -n openshift > mongodb-24persistent.json

   Edit L80 of mongodb-24persistent.json; replace **mongodb:latest** with **mongodb:2.4**.

   $ oc new-app --template=mongodb-persistent -n <project-name-that-template-was-created-in> \
     MONGODB_USER=user_from_v2_app -p \
     MONGODB_PASSWORD=password_from_v2_db -p \
     MONGODB_DATABASE=v2_dbname -p \
     MONGODB_ADMIN_PASSWORD=password_from_v2_db
   $ oc get pods

5. When the mongodb pod is up and running, copy the database archive files to the v3 MongoDB pod:

   $ oc rsync local/path/to/mongodump <mongodb_pod_name>:/var/lib/mongodb/data
   $ oc rsh <mongodb_pod>

6. In the MongoDB pod, complete the following for each database you want to restore:

   $ cd /var/lib/mongodb/data/mongodump
   $ tar -xzvf dbname.tar.gz
   $ mongorestore -u $MONGODB_USER -p $MONGODB_PASSWORD -d dbname -v /var/lib/mongodb/data/mongodump

7. Check if the database is restored:

   $ mongo admin -u $MONGODB_USER -p $MONGODB_ADMIN_PASSWORD
   $ use dbname
   $ show collections
   $ exit

8. Remove the mongodump directory from the pod:

   $ rm -rf /var/lib/mongodb/data/mongodump

Supported MongoDB Environment Variables