From 95b584c07f6fcede76e17ba85d78a835c2aaa03c Mon Sep 17 00:00:00 2001
From: Matteo Scaramuccia <moodle@matteoscaramuccia.com>
Date: Fri, 11 Nov 2022 22:25:00 +0100
Subject: [PATCH] Support a connection to an external DB

---
 README.md                  | 27 +++++++++++++++++++++++++++
 base.yml                   |  1 +
 config.docker-template.php |  2 +-
 3 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 1f50cf9e29a..17afda0c753 100644
--- a/README.md
+++ b/README.md
@@ -219,6 +219,33 @@ When you change them, use `bin/moodle-docker-compose down && bin/moodle-docker-c
 | `MOODLE_DOCKER_APP_VERSION`               | no        | a valid [app docker image version](https://docs.moodle.org/dev/Moodle_App_Docker_images) | not set       | If set will start an instance of the Moodle app if the chrome browser is selected |
 | `MOODLE_DOCKER_APP_RUNTIME`               | no        | 'ionic3' or 'ionic5'                  | not set       | Set this to indicate the runtime being used in the Moodle app. In most cases, this can be ignored because the runtime is guessed automatically (except on Windows using the `.cmd` binary). In case you need to set it manually and you're not sure which one it is, versions 3.9.5 and later should be using Ionic 5. |
 
+## Use an external database
+
+You can use an external database by setting `MOODLE_DOCKER_DB*` internal environment variables.
+
+For example to connect to an external DB server hosted in Azure:
+
+```
+# Configure coordinates and credentials for the external DB instance.
+export MOODLE_DOCKER_DBHOST=instance-name.mysql.database.azure.com
+export MOODLE_DOCKER_DBNAME=moodle-external-db
+export MOODLE_DOCKER_DBUSER=instance-username
+export MOODLE_DOCKER_DBPASS="1nst@nc3-p@ssw0rd"
+# Start the docker environment.
+bin/moodle-docker-compose up -d
+...
+# Stop the docker environemnt.
+bin/moodle-docker-compose down
+# Unset the external DB instance refs.
+unset MOODLE_DOCKER_DBHOST MOODLE_DOCKER_DBNAME MOODLE_DOCKER_DBUSER MOODLE_DOCKER_DBPASS
+```
+
+Please note that the local DB server will be still available to allow e.g. the usage of the specific DB client to connect to the remote DB server:
+
+```
+bin/moodle-docker-compose exec db mysql -h instance-name.mysql.database.azure.com -u ******** -p'********' -e "SELECT VERSION();"
+```
+
 ## Using XDebug for live debugging
 
 The XDebug PHP Extension is not included in this setup and there are reasons not to include it by default.
diff --git a/base.yml b/base.yml
index f736b8fe7e5..ab2962dea24 100644
--- a/base.yml
+++ b/base.yml
@@ -8,6 +8,7 @@ services:
       - "${MOODLE_DOCKER_WWWROOT}:/var/www/html"
       - "${ASSETDIR}/web/apache2_faildumps.conf:/etc/apache2/conf-enabled/apache2_faildumps.conf"
     environment:
+      MOODLE_DOCKER_DBHOST: db
       MOODLE_DOCKER_DBNAME: moodle
       MOODLE_DOCKER_DBUSER: moodle
       MOODLE_DOCKER_DBPASS: "m@0dl3ing"
diff --git a/config.docker-template.php b/config.docker-template.php
index fb8597a3d9a..0945296ad55 100644
--- a/config.docker-template.php
+++ b/config.docker-template.php
@@ -6,7 +6,7 @@
 
 $CFG->dbtype    = getenv('MOODLE_DOCKER_DBTYPE');
 $CFG->dblibrary = 'native';
-$CFG->dbhost    = 'db';
+$CFG->dbhost    = getenv('MOODLE_DOCKER_DBHOST');
 $CFG->dbname    = getenv('MOODLE_DOCKER_DBNAME');
 $CFG->dbuser    = getenv('MOODLE_DOCKER_DBUSER');
 $CFG->dbpass    = getenv('MOODLE_DOCKER_DBPASS');