Ability to configure notifier database.

CHANGELOG.md

+- Role: notifier
+  - Added `NOTIFIER_DATABASE_ENGINE`, `NOTIFIER_DATABASE_NAME`, `NOTIFIER_DATABASE_USER`, `NOTIFIER_DATABASE_PASSWORD`, `NOTIFIER_DATABASE_HOST`, and `NOTIFIER_DATABASE_PORT` to be able to configure the `notifier` service to use a database engine other than sqlite. Defaults to local sqlite.
+  - Deprecated: `NOTIFIER_DB_DIR`: Please use `NOTIFIER_DATABASE_NAME` instead.
+
 - Role: elasticsearch
   - Replaced `elasticsearch_apt_key` and `elastic_search_apt_keyserver` with `elasticsearch_apt_key_url`
   - Updated elasticsearch version to 1.5.0

playbooks/roles/notifier/defaults/main.yml

 ---
 NOTIFIER_WEB_USER: "www-data"
 NOTIFIER_VENV_DIR: "{{ notifier_app_dir }}/virtualenvs/notifier"
-NOTIFIER_DB_DIR: "{{ notifier_app_dir }}/db"
 NOTIFIER_SOURCE_REPO: "https://github.com/edx/notifier.git"
 NOTIFIER_CODE_DIR: "{{ notifier_app_dir }}/src"
 NOTIFIER_VERSION: "master"
@@ -12,6 +11,14 @@ NOTIFIER_DIGEST_TASK_INTERVAL: "1440"
 NOTIFIER_FORUM_DIGEST_TASK_BATCH_SIZE: "5"
 NOTIFIER_FORUM_DIGEST_TASK_RATE_LIMIT: "60/m"
 
+NOTIFIER_DB_DIR: "{{ notifier_app_dir }}/db"  # Deprecated: use NOTIFIER_DATABASE_NAME instead
+NOTIFIER_DATABASE_NAME: "{{ NOTIFIER_DB_DIR }}/notifier.db"
+NOTIFIER_DATABASE_ENGINE: "django.db.backends.sqlite3"
+NOTIFIER_DATABASE_USER: ""
+NOTIFIER_DATABASE_PASSWORD: ""
+NOTIFIER_DATABASE_HOST: ""
+NOTIFIER_DATABASE_PORT: ""
+
 NOTIFIER_THEME_NAME: ""
 NOTIFIER_THEME_REPO: ""
 NOTIFIER_THEME_VERSION: "master"
@@ -90,7 +97,12 @@ notifier_env_vars:
   EMAIL_SENDER_POSTAL_ADDRESS: "{{ NOTIFIER_EMAIL_SENDER_POSTAL_ADDRESS }}"
   NOTIFIER_LANGUAGE: "{{ NOTIFIER_LANGUAGE }}"
   NOTIFIER_ENV: "{{ NOTIFIER_ENV }}"
-  NOTIFIER_DB_DIR: "{{ NOTIFIER_DB_DIR }}"
+  NOTIFIER_DATABASE_NAME: "{{ NOTIFIER_DATABASE_NAME }}"
+  NOTIFIER_DATABASE_ENGINE: "{{ NOTIFIER_DATABASE_ENGINE }}"
+  NOTIFIER_DATABASE_USER: "{{ NOTIFIER_DATABASE_USER }}"
+  NOTIFIER_DATABASE_PASSWORD: "{{ NOTIFIER_DATABASE_PASSWORD }}"
+  NOTIFIER_DATABASE_HOST: "{{ NOTIFIER_DATABASE_HOST }}"
+  NOTIFIER_DATABASE_PORT: "{{ NOTIFIER_DATABASE_PORT }}"
   EMAIL_BACKEND: "{{ NOTIFIER_EMAIL_BACKEND }}"
   EMAIL_HOST: "{{ NOTIFIER_EMAIL_HOST }}"
   EMAIL_PORT: "{{ NOTIFIER_EMAIL_PORT }}"