6.3. Procedures for Replacing courseware_studentmodulehistory

This topic provides procedures for updating to the new database and table configuration required by the courseware_studentmodulehistory change. It also includes the optional procedure for migrating all data from courseware_studentmodulehistory to coursewarehistoryextended_studentmodulehistoryextended.

Before you follow these procedures for your Open edX instance, be sure to review the different options for updating courseware_studentmodulehistory.

6.3.1. Step 1: Create the Database

6.3.1.1. Options for Creating the Database

For all fullstack and production instances that follow master, you must create a MySQL database and set users up. To do so, you can use one of these options.

Note

You must follow one of these procedures for all of your fullstack and production instances.

6.3.1.1.1. Use the Playbook to Create the Database

Follow the create_db_and_users.yml playbook to create the edxapp_csmh database and its users automatically.

You then choose an option for configuring the edxapp_csmh database.

6.3.1.1.2. Create the Database Manually

Create the MySQL database. For the edx.org and edX Edge instances, edX named this database edxapp_csmh.

Modify the following example command for your database users and naming schemes.

mysql> create database edxapp_csmh DEFAULT CHARACTER SET utf8;
mysql> grant SELECT,INSERT,UPDATE,DELETE on edxapp_csmh.* to 'edxapp001@hosts'
mysql> grant SELECT,INSERT,UPDATE,DELETE,ALTER,CREATE,DROP,INDEX on edxapp_csmh.* to 'migrate@hosts'

You then choose an option for configuring your new database.

6.3.2. Step 2: Configure the Database

6.3.2.1. Options for Configuring the Database

After you create the MySQL database and set users up, you update lms.auth.json to add configuration settings to the DATABASES section. To do so, you can use one of these options.

  • Use the edxapp.yml playbook to update your edxapp instances. If you choose to use this playbook, then master after 5 May 2016 will update lms.auth.json to set edxapp_databases in the DATABASES section for you.

    The playbook requires EDXAPP_MYSQL_CSMH_DB_NAME, EDXAPP_MYSQL_CSMH_USER, EDXAPP_MYSQL_CSMH_PASSWORD, EDXAPP_MYSQL_CSMH_HOST, EDXAPP_MYSQL_CSMH_PORT to be populated in the same way that the EDXAPP_MYSQL_... variables are populated in your Ansible overrides.

  • Update the DATABASES section in lms.auth.json manually. If you create the MySQL database yourself, you must use this option. For more information, see Update DATABASES Manually.

6.3.2.1.1. Update DATABASES Manually

If you create the MySQL database yourself, you configure the database by adding a clause to the lms.auth.json file.

  1. Open the edx/app/edxapp/lms.auth.json file in your text editor.

  2. In the DATABASES section, add configuration details for your new database. An example follows.

    "student_module_history": {
           "ENGINE": "django.db.backends.mysql",
           "HOST": "localhost",
           "NAME": "edxapp_csmh",
           "PASSWORD": "password",
           "PORT": "3306",
           "USER": "edxapp001"
       },
    

6.3.3. Step 3: Enable Writes to the New Table

Edit the lms.env.json file to set the ENABLE_CSMH_EXTENDED feature flag.

``"ENABLE_CSMH_EXTENDED": true``

Alternatively, you can use your current Ansible overrides for updating feature flags to make this change.

6.3.4. Step 4: Create the Table

6.3.4.1. Options for Creating the Table

After you create and configure the MySQL database and enable the new table, you create the new table. To do so, you can use one of these options.

  • Run Django migrations to create the coursewarehistoryextended_studentmodulehistoryextended table. The edxapp.yml playbook uses these scripts to run migrations. * /edx/bin/edxapp-migrate-lms * /edx/bin/edxapp-migrate-cms
  • Run migrations manually. For more information, see Run Migrations Manually.

After you bring your servers back online with this configuration, the system only writes records for interactions with CAPA problems to the coursewarehistoryextended_studentmodulehistoryextended table.

6.3.4.1.1. Run Migrations Manually

A summary of the manual steps for running migrations follows.

  1. Run cms migrations against the default database.
  2. Run lms migrations against the default database.
  3. Run cms migrations against the student_module_history database.
  4. Run lms migrations against the student_module_history database.

If you choose to run migrations manually, refer to the last few lines of the /edx/bin/edxapp-migrate-lms and /edx/bin/edxapp-migrate-cms scripts for the commands that you must run.

6.3.5. Optional Step 5: Migrate All Data to the New Table

After you complete all of the deployment steps (1-4) described above, you have the option to migrate all data from courseware_studentmodulehistory to coursewarehistoryextended_studentmodulehistoryextended. For more information about this optional procedure, see Migrate All Data to One Table.

Note

This procedure is suitable only for large production instances that require the operational benefits described in the Why Is A New Database Needed? topic.

6.3.5.1. Script Options for Migrating Data

EdX provides the following migration scripts. You select the one that applies to your database architecture.

  • migrate-separate-database-instances.sh applies to installations that set up the new database on a different database server than the default database.

  • migrate-same-database-instance.sh applies to installations that set up the new database on the same database server as the default database.

    Implementing this database architecture is simpler than setting up a separate database server, but it offers different operational benefits.

Both options require your installation to be running a deploy of Open edX that writes only to coursewarehistoryextended_studentmodulehistoryextended. You can restart either of the migrations if necessary.

6.3.5.1.1. Run the Script for Separate Database Servers

EdX selected the database architecture with separate database servers, and implemented it by creating a read replica and then severing it from production. This process ensures that you have a mostly up to date courseware_studentmodulehistory table, which is then copied to coursewarehistoryextended_studentmodulehistoryextended.

  1. Do a final mysqldump from the first (default) database server to the second (new) database server.

    mysqldump --skip-add-drop-table --no-create-info -u migrate -p -h dbhost db courseware_studentmodulehistory --where='id > LAST_ID' --result-file=catchup.sql
    

    Allow the mysqldump to run to completion, so that courseware_studentmodulehistory is caught up.

  2. Run migrate-separate-database-instances.sh to copy data slowly.

    mysql -u migrate -p -h newdbhost db2 < catchup.sql
    

    Be sure to monitor your progress to ensure that the process runs slowly, and does not cause disk contention or other performance issues on the new database instance.

6.3.5.1.2. Run the Script for A Single Database Server

Run migrate-same-database-instance.sh.

6.3.5.2. Restart a Migration

If you need to restart either migration, you can use the following command to find the largest ID value that was successfully inserted into the new table.

select max(id) from wwc.courseware_studentmodulehistory where id < MAXID

You can then rerun with MINID set to the result of this query.

6.3.5.3. Disable Reads from the Old Table

Edit the lms.env.json file to set the ENABLE_READING_FROM_MULTIPLE_HISTORY_TABLES feature flag.

"ENABLE_READING_FROM_MULTIPLE_HISTORY_TABLES": false

After you bring your servers back online with this configuration, the system only writes to and queries from the coursewarehistoryextended_studentmodulehistoryextended table.

6.3.5.4. Truncate the Old Table

Select one of the available MySQL techniques for slowly draining the courseware_studentmodulehistory table.

  • The preferred technique for installations with small or moderately sized databases is the TRUNCATE TABLE courseware_studentmodulehistory command. However, this command can cause a lot of disk activity.
  • If your table is very large, you can choose to use the slow-delete.sh script instead. EdX prepared and used this script to truncate courseware_studentmodulehistory.