What is Memcached?

Memcached is an in-memory key-value store for small chunks of arbitrary data (strings, objects) from results of database calls, API calls, or page rendering.

memcached.org

TLDR

docker run --name memcached bitnami/memcached:latest

Docker Compose

version: '2'

services:
  memcached:
    image: 'bitnami/memcached:latest'
    ports:
      - '11211:11211'

Get this image

The recommended way to get the Bitnami Memcached Docker Image is to pull the prebuilt image from the Docker Hub Registry.

docker pull bitnami/memcached:latest

To use a specific version, you can pull a versioned tag. You can view the list of available versions in the Docker Hub Registry.

docker pull bitnami/memcached:[TAG]

If you wish, you can also build the image yourself.

docker build -t bitnami/memcached:latest https://github.com/bitnami/bitnami-docker-memcached.git

Linking

If you want to connect to your Memcached server inside another container, you can use the linking system provided by Docker.

Connecting your app container to the Memcached server container

Step 1: Run the Memcached image with a specific name

The first step is to start our Memcached server.

Docker's linking system uses container ids or names to reference containers. We can explicitly specify a name for our Memcached server to make it easier to connect to other containers.

docker run --name memcached bitnami/memcached:latest

Step 2: Run your app and link to our server

Now that we have our Memcached server running, we can create another container that links to it by giving Docker the --link option. This option takes the id or name of the container we want to link it to as well as a hostname to use inside the container, separated by a colon. For example, to have our Memcached server accessible in another container with memcached as it's hostname we would pass --link memcached:memcached to the Docker run command.

docker run -it --link memcached:memcached myapp

Inside myapp, use memcached as the hostname for the Memcached server.

Linking with Docker Compose

Step 1: Add a Memcached entry in your docker-compose.yml

Copy the snippet below into your docker-compose.yml to add Memcached to your application.

services:
  memcached:
    image: 'bitnami/memcached:latest'

Step 2: Link it to another container in your application

Update the definitions for containers you want to access your Memcached server from to include a link to the memcached entry you added in Step 1.

services:
  myapp:
    image: myapp
    depends_on:
      - memcached

Configuration

Creating the Memcached admin user

Authentication on the Memcached server is disabled by default. To enable authentication, specify a username and password for the Memcached admin user using the MEMCACHED_USERNAME and MEMCACHED_PASSWORD environment variables.

docker run --name memcached \
  -e MEMCACHED_USERNAME=my_user \
  -e MEMCACHED_PASSWORD=my_password \
  bitnami/memcached:latest

or using Docker Compose:

version: '2'

services:
  memcached:
    image: 'bitnami/memcached:latest'
    ports:
      - '11211:11211'
    environment:
      - MEMCACHED_USERNAME=my_user
      - MEMCACHED_PASSWORD=my_password

The default value of the MEMCACHED_USERNAME is root.

Logging

The Bitnami Memcached Docker image sends the container logs to the stdout. To view the logs:

docker logs memcached

or using Docker Compose:

docker-compose logs memcached

You can configure the containers logging driver using the --log-driver option if you wish to consume the container logs differently. In the default configuration docker uses the json-file driver.

Maintenance

Upgrade this image

Bitnami provides up-to-date versions of Memcached, including security patches, soon after they are made upstream. We recommend that you follow these steps to upgrade your container.

Step 1: Get the updated image

docker pull bitnami/memcached:latest

or if you're using Docker Compose, update the value of the image property to bitnami/memcached:latest.

Step 2: Remove the currently running container

docker rm -v memcached

or using Docker Compose:

docker-compose rm -v memcached

Step 3: Run the new image

Re-create your container from the new image.

docker run --name memcached bitnami/memcached:latest

or using Docker Compose:

docker-compose start memcached

Testing

This image is tested for expected runtime behavior, using the Bats testing framework. You can run the tests on your machine using the bats command.

bats test.sh

Notable Changes

1.4.25-r4

• MEMCACHED_USER parameter has been renamed to MEMCACHED_USERNAME.

1.4.25-r0

• The logs are always sent to the stdout and are no longer collected in the volume.

Contributing

We'd love for you to contribute to this container. You can request new features by creating an issue, or submit a pull request with your contribution.

Issues

If you encountered a problem running this container, you can file an issue. For us to provide better support, be sure to include the following information in your issue:

• Host OS and version
• Docker version (docker version)
• Output of docker info
• Version of this container (echo $BITNAMI_IMAGE_VERSION inside the container)
• The command you used to run the container, and any relevant output you saw (masking any sensitive information)

License

Copyright (c) 2015-2016 Bitnami

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.