Migrating from the Cloudera Manager Embedded PostgreSQL Database Server to an External PostgreSQL Database

Cloudera Manager provides an embedded PostgreSQL database server for demonstration and proof of concept deployments when creating a cluster. To remind users that this embedded database is not suitable for production, Cloudera Manager displays the banner text: "You are running Cloudera Manager in non-production mode, which uses an embedded PostgreSQL database. Switch to using a supported external database before moving into production."

If, however, you have already used the embedded database, and you are unable to redeploy a fresh cluster, then you must migrate to an external PostgreSQL database.

Continue reading:

Prerequisites
Identify Roles that Use the Embedded Database Server
Migrate Databases from the Embedded Database Server to the External PostgreSQL Database Server

Prerequisites

Before migrating the Cloudera Manager embedded PostgreSQL database to an external PostgreSQL database, ensure that your setup meets the following conditions:

The external PostgreSQL database server is running.
The database server is configured to accept remote connections.
The database server is configured to accept user logins using md5.
No one has manually created any databases in the external database server for roles that will be migrated.
Note: To view a list of databases in the external database server (requires default superuser permission):
```
sudo -u postgres psql -l
```
All health issues with your cluster have been resolved.

For details about configuring the database server, see Configuring and Starting the PostgreSQL Server.

For large clusters, Cloudera recommends running your database server on a dedicated host. Engage Cloudera Professional Services or a certified database administrator to correctly tune your external database server.

Identify Roles that Use the Embedded Database Server

Before you can migrate to another database server, you must first identify the databases using the embedded database server. When the Cloudera Manager Embedded Database server is initialized, it creates the Cloudera Manager database and databases for roles in the Management Services. The Installation Wizard (which runs automatically the first time you log in to Cloudera Manager) or Add Service action for a cluster creates additional databases for roles when run. It is in this context that you identify which roles are used in the embedded database server.

To identify which roles are using the Cloudera Manager embedded database server:

Obtain and save the cloudera-scm superuser password from the embedded database server. You will need this password in subsequent steps:
```
head -1  /var/lib/cloudera-scm-server-db/data/generated_password.txt
```

Make a list of all services that are using the embedded database server. Then, after determining which services are not using the embedded database server, remove those services from the list. The scm database must remain in your list. Use the following table as a guide:

Cloudera Manager Embedded Database Server Databases
Service	Role	Default Database Name	Default Username
Cloudera Manager Server		scm	scm
Cloudera Management Service	Activity Monitor	amon	amon
Hive	Hive Metastore Server	hive	hive
Hue	Hue Server	hue	7uu7uu7uhue
Cloudera Management Service	Navigator Audit Server	nav	nav
Cloudera Management Service	Navigator Metadata Server	navms	navms
Oozie	Oozie Server	oozie_oozie_server	oozie_oozie_server
Cloudera Management Service	Reports Manager	rman	rman
Sentry	Sentry Server	sentry	sentry

Verify which roles are using the embedded database. Roles using the embedded database server always use port 7432 (the default port for the embedded database) on the Cloudera Manager Server host.

For Cloudera Management Services:
1. Select Cloudera Management Service > Configuration, and type "7432" in the Search field.
2. Confirm that the hostname for the services being used is the same hostname used by the Cloudera Manager Server.
Note:
If any of the following fields contain the value "7432", then the service is using the embedded database:
- Activity Monitor
- Navigator Audit Server
- Navigator Metadata Server
- Reports Manager
For the Oozie Service:
1. Select Oozie service > Configuration, and type "7432" in the Search field.
2. Confirm that the hostname is the Cloudera Manager Server.
For Hive, Hue, and Sentry Services:
1. Select the specific service > Configuration, and type "database host" in the Search field.
2. Confirm that the hostname is the Cloudera Manager Server.
3. In the Search field, type “database port” and confirm that the port is 7432.
4. Repeat these steps for each of the services (Hive, Hue and Sentry).

Verify the database names in the embedded database server match the database names on your list (Step 2). Databases that exist on the database server and not used by their roles do not need to be migrated. This step is to confirm that your list is correct.

psql -h localhost -p 7432 -U cloudera-scm -l

Password for user cloudera-scm: <password>

                                               List of databases
       Name        |       Owner        | Encoding |  Collate   |   Ctype    |         Access
--------------------+--------------------+----------+------------+------------+----------------
amon               | amon               | UTF8     | en_US.UTF8 | en_US.UTF8 |
hive               | hive               | UTF8     | en_US.UTF8 | en_US.UTF8 |
hue                | hue                | UTF8     | en_US.UTF8 | en_US.UTF8 |
nav                | nav                | UTF8     | en_US.UTF8 | en_US.UTF8 |
navms              | navms              | UTF8     | en_US.UTF8 | en_US.UTF8 |
oozie_oozie_server | oozie_oozie_server | UTF8     | en_US.UTF8 | en_US.UTF8 |
postgres           | cloudera-scm       | UTF8     | en_US.UTF8 | en_US.UTF8 |
rman               | rman               | UTF8     | en_US.UTF8 | en_US.UTF8 |
scm                | scm                | UTF8     | en_US.UTF8 | en_US.UTF8 |
sentry             | sentry             | UTF8     | en_US.UTF8 | en_US.UTF8 |
template0          | cloudera-scm       | UTF8     | en_US.UTF8 | en_US.UTF8 | =c/"cloudera-scm"
template1          | cloudera-scm       | UTF8     | en_US.UTF8 | en_US.UTF8 | =c/"cloudera-scm"
(12 rows)

You should now have a list of all roles and database names that use the embedded database server, and are ready to proceed with the migration of databases from the embedded database server to the external PostgreSQL database server.

Migrate Databases from the Embedded Database Server to the External PostgreSQL Database Server

While performing this procedure, ensure that the Cloudera Manager Agents remain running on all hosts. Unless otherwise specified, when prompted for a password use the cloudera-scm password.

In Cloudera Manager, stop the cluster services identified as using the embedded database server (see Identify Roles that Use the Embedded Database Server). Refer to Starting, Stopping, and Restarting Services for details about how to stop cluster services. Be sure to stop the Cloudera Management Service as well. Also be sure to stop any services with dependencies on these services. The remaining CDH services will continue to run without downtime.
Note: If you do not stop the services from within Cloudera Manager before stopping Cloudera Manager Server from the command line, they will continue to run and maintain a network connection to the embedded database server. If this occurs, then the embedded database server will ignore any command line stop commands (Step 2) and require that you manually kill the process, which in turn causes the services to crash instead of stopping cleanly.
Navigate to Hosts > All Hosts, and make note of the number of roles assigned to hosts. Also take note whether or not they are in a commissioned state. You will need this information later to validate that your scm database was migrated correctly.
Stop the Cloudera Manager Server. To stop the server:
```
sudo service cloudera-scm-server stop
```
Obtain and save the embedded database superuser password (you will need this password in subsequent steps) from the generated_password.txt file:
```
head -1  /var/lib/cloudera-scm-server-db/data/generated_password.txt
```
Export the PostgreSQL user roles from the embedded database server to ensure the correct users, permissions, and passwords are preserved for database access. Passwords are exported as an md5sum and are not visible in plain text. To export the database user roles (you will need the cloudera-scm user password):
```
pg_dumpall -h localhost -p 7432 -U cloudera-scm -v --roles-only -f "/var/tmp/cloudera_user_roles.sql"
```
Edit /var/tmp/cloudera_user_roles.sql to remove any CREATE ROLE and ALTER ROLE commands for databases not in your list. Leave the entries for cloudera-scm untouched, because this user role is used during the database import.

Export the data from each of the databases on your list you created in Identify Roles that Use the Embedded Database Server:

pg_dump -F c -h localhost -p 7432 -U cloudera-scm [database_name]  > /var/tmp/[database_name]_db_backup-$(date +”%m-%d-%Y”).dump

Following is a sample data export command for the scm database:

pg_dump -F c -h localhost -p 7432 -U cloudera-scm scm > /var/tmp/scm_db_backup-$(date +%m-%d-%Y).dump

Password:

Stop and disable the embedded database server:
```
service cloudera-scm-server-db stop
chkconfig cloudera-scm-server-db off
```
Confirm that the embedded database server is stopped:
```
netstat -at | grep 7432
```

Back up the Cloudera Manager Server database configuration file:

cp /etc/cloudera-scm-server/db.properties /etc/cloudera-scm-server/db.properties.embedded

Copy the file /var/tmp/cloudera_user_roles.sql and the database dump files from the embedded database server host to /var/tmp on the external database server host:
```
cd /var/tmp
scp cloudera_user_roles.sql *.dump <user>@<postgres-server>:/var/tmp
```
Import the PostgreSQL user roles into the external database server.
The external PostgreSQL database server superuser password is required to import the user roles. If the superuser role has been changed, you will be prompted for the username and password.
Note: Only run the command that applies to your context; do not execute both commands.
- To import users when using the default PostgreSQL superuser role:
```
sudo -u postgres psql -f /var/tmp/cloudera_user_roles.sql
```
- To import users when the superuser role has been changed:
```
psql -h <database-hostname> -p <database-port> -U <superuser> -f /var/tmp/cloudera_user_roles.sql
```
  For example:
```
psql -h pg-server.example.com -p 5432 -U postgres -f /var/tmp/cloudera_user_roles.sql
```
```
Password for user postgres
```
Import the Cloudera Manager database on the external server. First copy the database dump files from the Cloudera Manager Server host to your external PostgreSQL database server, and then import the database data:
Note: To successfully run the pg_restore command, there must be an existing database on the database server to complete the connection; the existing database will not be modified. If the -d <existing-database> option is not included, then the pg_restore command will fail.
```
pg_restore -C -h <database-hostname> -p <database-port> -d <existing-database> -U cloudera-scm -v <data-file>
```
Repeat this import for each database.
The following example is for the scm database:
```
pg_restore -C -h pg-server.example.com -p 5432 -d postgres -U cloudera-scm -v /var/tmp/scm_server_db_backup-20180312.dump
```
```
pg_restore: connecting to database for restore
Password:
```
Update the Cloudera Manager Server database configuration file to use the external database server. Edit the /etc/cloudera-scm-server/db.properties file as follows:
1. Update the com.cloudera.cmf.db.host value with the hostname and port number of the external database server.
2. Change the com.cloudera.cmf.db.setupType value from "EMBEDDED" to "EXTERNAL".
Start the Cloudera Manager Server and confirm it is working:
```
service cloudera-scm-server start
```
Note that if you start the Cloudera Manager GUI at this point, it may take up to five minutes after executing the start command before it becomes available.
In Cloudera Manager Server, navigate to Hosts > All Hosts and confirm the number of roles assigned to hosts (this number should match what you found in Step 2); also confirm that they are in a commissioned state that matches what you observed in Step 2.
Update the role configurations to use the external database hostname and port number. Only perform this task for services where the database has been migrated.
For Cloudera Management Services:
1. Select Cloudera Management Service > Configuration, and type "7432" in the Search field.
2. Change any database hostname properties from the embedded database to the external database hostname and port number.
3. Click Save Changes.
For the Oozie Service:
1. Select Oozie service > Configuration, and type "7432" in the Search field.
2. Change any database hostname properties from the embedded database to the external database hostname and port number.
3. Click Save Changes.
For Hive, Hue, and Sentry Services:
1. Select the specific service > Configuration, and type "database host" in the Search field.
2. Change the hostname from the embedded database name to the external database hostname.
3. Click Save Changes.
Start the Cloudera Management Service and confirm that all management services are up and no health tests are failing.
Start all Services via the Cloudera Manager web UI. This should start all services that were stopped for the database migration. Confirm that all services are up and no health tests are failing.
On the embedded database server host, remove the embedded PostgreSQL database server:
1. Make a backup of the /var/lib/cloudera-scm-server-db/data directory:
```
tar czvf /var/tmp/embedded_db_data_backup-$(date +”%m-%d-%Y”).tgz /var/lib/cloudera-scm-server-db/data
```
2. Remove the embedded database package:
  For RHEL/SLES:
```
rpm --erase cloudera-manager-server-db-2
```
  For Debian/Ubuntu:
```
apt-get remove cloudera-manager-server-db-2
```
3. Delete the /var/lib/cloudera-scm-server-db/data directory.

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