[GitHub] [druid] FrankChen021 commented on a change in pull request #11463: Add details to the Docker tutorial

[GitBox <gi...@apache.org>]

FrankChen021 commented on a change in pull request #11463:
URL: https://github.com/apache/druid/pull/11463#discussion_r683117361



##########
File path: docs/tutorials/docker.md
##########
@@ -21,67 +21,108 @@ title: "Docker"
   ~ specific language governing permissions and limitations
   ~ under the License.
   -->
-  
+
 In this quickstart, we will download the Apache Druid image from [Docker Hub](https://hub.docker.com/r/apache/druid) and set it up on a single machine using [Docker](https://www.docker.com/get-started) and [Docker Compose](https://docs.docker.com/compose/). The cluster will be ready to load data after completing this initial setup.
 
-Before beginning the quickstart, it is helpful to read the [general Druid overview](../design/index.md) and the [ingestion overview](../ingestion/index.md), as the tutorials will refer to concepts discussed on those pages. Additionally, familiarity with Docker is recommended.
+Before beginning the quickstart, it is helpful to read the [general Druid overview](../design/index.md) and the [ingestion overview](../ingestion/index.md), as the tutorials will refer to concepts discussed on those pages. Additionally, familiarity with [Docker](https://www.docker.com/get-started) is recommended.
+
+This tutorial assumes you will download the required files from GitHub. The files are also available in a Druid installation and in the Druid sources.
 
 ## Prerequisites
 
-* Docker
+* [Docker](https://www.docker.com/get-started)
 
 ## Getting started
 
-The Druid source code contains [an example `docker-compose.yml`](https://github.com/apache/druid/blob/{{DRUIDVERSION}}/distribution/docker/docker-compose.yml) which can pull an image from Docker Hub and is suited to be used as an example environment and to experiment with Docker based Druid configuration and deployments.
+Create a directory to hold the Druid Docker files.
+
+The Druid source code contains [an example `docker-compose.yml`](https://github.com/apache/druid/blob/{{DRUIDVERSION}}/distribution/docker/docker-compose.yml) which pulls an image from Docker Hub and is suited to be used as an example environment and to experiment with Docker based Druid configuration and deployments. [Download](https://raw.githubusercontent.com/apache/druid/{{DRUIDVERSION}}/distribution/docker/docker-compose.yml) this file to the directory created above.
 
 ### Compose file
 
-The example `docker-compose.yml` will create a container for each Druid service, as well as ZooKeeper and a PostgreSQL container as the metadata store. 
+The example `docker-compose.yml` will create a container for each Druid service, as well as ZooKeeper and a PostgreSQL container as the metadata store.
 
-It will also create a named volumes `druid_shared`, which is mounted as `opt/shared` in container, as deep storage to keep and share segments and task logs among Druid services.
+It will also create a named volume `druid_shared` as deep storage to keep and share segments and task logs among Druid services. The volume is mounted as `opt/shared` in the container.
 
-The Druid containers are configured via an [environment file](https://github.com/apache/druid/blob/{{DRUIDVERSION}}/distribution/docker/environment).
+### Environment file
+
+The Druid `docker-compose.yml` example utilizes an [environment file](https://docs.docker.com/compose/environment-variables/#the-env_file-configuration-option) to specify the complete Druid configuration, including the environment variables listed below. This file is named `environment` by default, and must be in the same directory as the `docker-compose.yml` file. [Download](https://raw.githubusercontent.com/apache/druid/{{DRUIDVERSION}}/distribution/docker/environment) the example `environment` file to the directory created above. The options in this file work well for trying Druid and for using the tutorial.
+
+The single-file approach is inadequate for a production system. Instead we suggest using either `DRUID_COMMON_CONFIG` and `DRUID_CONFIG_${service}` or specially tailored, service-specific environment files.
 
 ### Configuration
 
-Configuration of the Druid Docker container is done via environment variables, which may additionally specify paths to [the standard Druid configuration files](../configuration/index.md)
+Configuration of the Druid Docker container is done via environment variables set within the container. Docker Compose passes the values from the `environment file` into the container. The variables may additionally specify paths to [the standard Druid configuration files](../configuration/index.md) which must be available within the container.
+
+The default values are fine for the Quickstart. Production systems will want to modify the defaults.
 
-Special environment variables:
+Basic configuration:
+
+* `DRUID_MAXDIRECTMEMORYSIZE` -- set Java max direct memory size. Default is 6 GB.

Review comment:
       In docker config, the value is '6172m', which is '6 GiB'. so the doc here should use the binary format '6 GiB'.




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