Merge pull request #299 from Silthus/master

feat(minecraft-server): replace environment variables in configs

minecraft-server/Dockerfile

@@ -3,19 +3,19 @@ FROM openjdk:8u171-jre-alpine
 LABEL maintainer "itzg"
 
 RUN apk add --no-cache -U \
-          openssl \
-          imagemagick \
-          lsof \
-          su-exec \
-          shadow \
-          bash \
-          curl iputils wget \
-          git \
-          jq \
-          mysql-client \
-          tzdata \
-          rsync \
-          python python-dev py2-pip
+  openssl \
+  imagemagick \
+  lsof \
+  su-exec \
+  shadow \
+  bash \
+  curl iputils wget \
+  git \
+  jq \
+  mysql-client \
+  tzdata \
+  rsync \
+  python python-dev py2-pip
 
 RUN pip install mcstatus
 
@@ -71,7 +71,8 @@ ENV UID=1000 GID=1000 \
   JVM_XX_OPTS="-XX:+UseG1GC" MEMORY="1G" \
   TYPE=VANILLA VERSION=LATEST FORGEVERSION=RECOMMENDED SPONGEBRANCH=STABLE SPONGEVERSION= LEVEL=world \
   PVP=true DIFFICULTY=easy ENABLE_RCON=true RCON_PORT=25575 RCON_PASSWORD=minecraft \
-  LEVEL_TYPE=DEFAULT GENERATOR_SETTINGS= WORLD= MODPACK= MODS= SERVER_PORT=25565 ONLINE_MODE=TRUE CONSOLE=true SERVER_NAME="Dedicated Server"
+  LEVEL_TYPE=DEFAULT GENERATOR_SETTINGS= WORLD= MODPACK= MODS= SERVER_PORT=25565 ONLINE_MODE=TRUE CONSOLE=true SERVER_NAME="Dedicated Server" \
+  REPLACE_ENV_VARIABLES="FALSE" ENV_VARIABLE_PREFIX="CFG_"
 
 COPY start* /
 RUN dos2unix /start* && chmod +x /start*

minecraft-server/README.md

@@ -202,6 +202,85 @@ This works well if you want to have a common set of modules in a separate
 location, but still have multiple worlds with different server requirements
 in either persistent volumes or a downloadable archive.
 
+### Replacing variables inside configs
+
+Sometimes you have mods or plugins that require configuration information that is only available at runtime.
+For example if you need to configure a plugin to connect to a database,
+you don't want to include this information in your Git repository or Docker image.
+Or maybe you have some runtime information like the server name that needs to be set
+in your config files after the container starts.
+
+For those cases there is the option to replace defined variables inside your configs
+with environment variables defined at container runtime.
+
+If you set the enviroment variable `REPLACE_ENV_VARIABLES` to `TRUE` the startup script
+will go thru all files inside your `/data` volume and replace variables that match your 
+defined environment variables. Variables that you want to replace need to be wrapped
+inside `${YOUR_VARIABLE}` curly brackets and prefixed with a dollar sign. This is the regular
+syntax for enviromment variables inside strings or config files.
+
+Optionally you can also define a prefix to only match predefined enviroment variables.
+
+`ENV_VARIABLE_PREFIX="CFG_"` <-- this is the default prefix
+
+There are some limitations to what characters you can use.
+
+| Type  | Allowed Characters  |
+| ----- | ------------------- |
+| Name  | `0-9a-zA-Z_-`       |
+| Value | `0-9a-zA-Z_-:/=?.+` |
+
+Here is a full example where we want to replace values inside a `database.yml`.
+
+```yml
+...
+database:
+    host: ${CFG_DB_HOST}
+    name: ${CFG_DB_NAME}
+    password: ${CFG_DB_PASSWORD}
+```
+
+This is how your `docker-compose.yml` file could look like:
+
+```yml
+version: '3'
+# Other docker-compose examples in /examples
+
+services:
+  minecraft:
+    image: itzg/minecraft-server
+    ports:
+      - "25565:25565"
+    volumes:
+      - "mc:/data"
+    environment:
+      EULA: "TRUE"
+      CONSOLE: "false"
+      ENABLE_RCON: "true"
+      RCON_PASSWORD: "testing"
+      RCON_PORT: 28016
+      # enable env variable replacement
+      REPLACE_ENV_VARIABLES: "TRUE"
+      # define an optional prefix for your env variables you want to replace
+      ENV_VARIABLE_PREFIX: "CFG_"
+      # and here are the actual variables
+      CFG_DB_HOST: "http://localhost:3306"
+      CFG_DB_NAME: "minecraft"
+      CFG_DB_PASSWORD: "ug23u3bg39o-ogADSs"
+    restart: always
+  rcon:
+    image: itzg/rcon
+    ports:
+      - "4326:4326"
+      - "4327:4327"
+    volumes:
+      - "rcon:/opt/rcon-web-admin/db"
+
+volumes:
+  mc:
+  rcon:
+```
+
 ## Running a Bukkit/Spigot server
 
 Enable Bukkit/Spigot server mode by adding a `-e TYPE=BUKKIT -e VERSION=1.8` or `-e TYPE=SPIGOT -e VERSION=1.8` to your command-line.

minecraft-server/start-finalSetup04ServerProperties

@@ -132,4 +132,4 @@ else
   echo "server.properties already created, skipping"
 fi
 
-exec /start-minecraftFinalSetup $@
+exec /start-finalSetup05EnvVariables $@

minecraft-server/start-finalSetup05EnvVariables

@@ -0,0 +1,15 @@
+#!/bin/bash
+
+if [ "$REPLACE_ENV_VARIABLES" = "TRUE" ]; then
+  echo "Replacing env variables in configs that match the prefix $ENV_VARIABLE_PREFIX..."
+  while IFS='=' read -r name value ; do
+    # check if name of env variable matches the prefix
+    # sanity check environment variables to avoid code injections
+    if [[ "$name" = $ENV_VARIABLE_PREFIX* ]] && [[ $value =~ ^[0-9a-zA-Z_:/=?.+\-]*$ ]] && [[ $name =~ ^[0-9a-zA-Z_\-]*$ ]]; then
+        echo "Replacing $name with $value ..."
+        find /data/ -type f \( -name "*.yml" -or -name "*.yaml" -or -name "*.txt" -or -name "*.cfg" -or -name "*.properties" \) -exec sed -i 's#${'"$name"'}#'"$value"'#g' {} \;
+    fi
+  done < <(env)
+fi
+
+exec /start-minecraftFinalSetup $@