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

TL;DR

$ docker run --name memcached bitnami/memcached:latest

Docker Compose

$ curl -sSL https://raw.githubusercontent.com/bitnami/bitnami-docker-memcached/master/docker-compose.yml > docker-compose.yml
$ docker-compose up -d

Why use Bitnami Images?

• Bitnami closely tracks upstream source changes and promptly publishes new versions of this image using our automated systems.
• With Bitnami images the latest bug fixes and features are available as soon as possible.
• Bitnami containers, virtual machines and cloud images use the same components and configuration approach - making it easy to switch between formats based on your project needs.
• All our images are based on minideb a minimalist Debian based container image which gives you a small base container image and the familiarity of a leading Linux distribution.
• All Bitnami images available in Docker Hub are signed with Docker Content Trust (DCT). You can use DOCKER_CONTENT_TRUST=1 to verify the integrity of the images.
• Bitnami container images are released daily with the latest distribution packages available.

This CVE scan report contains a security report with all open CVEs. To get the list of actionable security issues, find the "latest" tag, click the vulnerability report link under the corresponding "Security scan" field and then select the "Only show fixable" filter on the next page.

How to deploy Memcached in Kubernetes?

Deploying Bitnami applications as Helm Charts is the easiest way to get started with our applications on Kubernetes. Read more about the installation in the Bitnami Memcached Chart GitHub repository.

Bitnami containers can be used with Kubeapps for deployment and management of Helm Charts in clusters.

Why use a non-root container?

Non-root container images add an extra layer of security and are generally recommended for production environments. However, because they run as a non-root user, privileged tasks are typically off-limits. Learn more about non-root containers in our docs.

Supported tags and respective Dockerfile links

Learn more about the Bitnami tagging policy and the difference between rolling tags and immutable tags in our documentation page.

• 1, 1-debian-10, 1.6.7, 1.6.7-debian-10-r36, latest (1/debian-10/Dockerfile)

Subscribe to project updates by watching the bitnami/memcached GitHub repo.

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#master:1/debian-10'

Connecting to other containers

Using Docker container networking, a Memcached server running inside a container can easily be accessed by your application containers.

Containers attached to the same network can communicate with each other using the container name as the hostname.

Using the Command Line

Step 1: Create a network

$ docker network create app-tier --driver bridge

Step 2: Launch the Memcached server instance

Use the --network app-tier argument to the docker run command to attach the Memcached container to the app-tier network.

$ docker run -d --name memcached-server \
    --network app-tier \
    bitnami/memcached:latest

Step 3: Launch your application container

$ docker run -d --name myapp \
    --network app-tier \
    YOUR_APPLICATION_IMAGE

IMPORTANT:

1. Please update the YOUR_APPLICATION_IMAGE_ placeholder in the above snippet with your application image
2. In your application container, use the hostname memcached-server to connect to the Memcached server

Using Docker Compose

When not specified, Docker Compose automatically sets up a new network and attaches all deployed services to that network. However, we will explicitly define a new bridge network named app-tier. In this example we assume that you want to connect to the Memcached server from your own custom application image which is identified in the following snippet by the service name myapp.

version: '2'

networks:
  app-tier:
    driver: bridge

services:
  memcached:
    image: 'bitnami/memcached:latest'
    networks:
      - app-tier
  myapp:
    image: 'YOUR_APPLICATION_IMAGE'
    networks:
      - app-tier

IMPORTANT:

1. Please update the YOUR_APPLICATION_IMAGE_ placeholder in the above snippet with your application image
2. In your application container, use the hostname memcached to connect to the Memcached server

Launch the containers using:

$ docker-compose up -d

Configuration

Specify the cache size

By default, the Bitnami Memcached container will not specify any cache size and will start with Memcached defaults (64MB). You can specify a different value with the MEMCACHED_CACHE_SIZE environment variable (in MB).

$ docker run --name memcached -e MEMCACHED_CACHE_SIZE=128 bitnami/memcached:latest

or by modifying the docker-compose.yml file present in this repository:

services:
  memcached:
  ...
    environment:
      - MEMCACHED_CACHE_SIZE=128
  ...

Specify maximum number of concurrent connections

By default, the Bitnami Memcached container will not specify any maximum number of concurrent connections and will start with Memcached defaults (1024 concurrent connections). You can specify a different value with the MEMCACHED_MAX_CONNECTIONS environment variable.

$ docker run --name memcached -e MEMCACHED_MAX_CONNECTIONS=2000 bitnami/memcached:latest

or by modifying the docker-compose.yml file present in this repository:

services:
  memcached:
  ...
    environment:
      - MEMCACHED_MAX_CONNECTIONS=2000
  ...

Specify number of threads to process requests

By default, the Bitnami Memcached container will not specify the amount of threads for which to process requests for and will start with Memcached defaults (4 threads). You can specify a different value with the MEMCACHED_THREADS environment variable.

$ docker run --name memcached -e MEMCACHED_THREADS=4 bitnami/memcached:latest

or by modifying the docker-compose.yml file present in this repository:

services:
  memcached:
  ...
    environment:
      - MEMCACHED_THREADS=4
  ...

Creating the Memcached admin user

Authentication on the Memcached server is disabled by default. To enable authentication, specify the password for the Memcached admin user using the MEMCACHED_PASSWORD environment variable (or in the content of the file specified in MEMCACHED_PASSWORD_FILE).

To customize the username of the Memcached admin user, which defaults to root, the MEMCACHED_USERNAME variable should be specified.

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

or by modifying the docker-compose.yml file present in this repository:

version: '2'

services:
  memcached:
  ...
    environment:
      - MEMCACHED_USERNAME=my_user
      - MEMCACHED_PASSWORD=my_password
  ...

The default value of the MEMCACHED_USERNAME is root.

Passing extra command-line flags to memcached

Passing extra command-line flags to the Memcached service command is possible by adding them as arguments to run.sh script:

$ docker run --name memcached bitnami/memcached:latest /opt/bitnami/scripts/memcached/run.sh -vvv

Alternatively, modify the docker-compose.yml file present in this repository:

services:
  memcached:
  ...
    command: /opt/bitnami/scripts/memcached/run.sh -vvv
  ...

Refer to the Memcached man page for the complete list of arguments.

Using custom SASL configuration

In order to load your own SASL configuration file, you will have to make them available to the container. You can do it doing the following:

• Mounting a volume with your custom configuration
• Adding custom configuration via environment variable.

By default, when authentication is enabled the SASL configuration of Memcached is written to /opt/bitnami/memcached/sasl2/memcached.conf file with the following content:

mech_list: plain
sasldb_path: /opt/bitnami/memcached/conf/memcachedsasldb

The /opt/bitnami/memcached/conf/memcachedsasldb is the path to the sasldb file that contains the list of Memcached users.

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 up memcached

Notable Changes

1.5.18-debian-9-r13 and 1.5.19-ol-7-r1

• Fixes regression in Memcached Authentication introduced in release 1.5.18-debian-9-r6 and 1.5.18-ol-7-r7 (#62).

1.5.18-debian-9-r6 and 1.5.18-ol-7-r7

• Decrease the size of the container. The configuration logic is now based on Bash scripts in the `rootfs/ folder.
• Custom SASL configuration should be mounted at /opt/bitnami/memcached/conf/sasl2/ instead of /bitnami/memcached/conf/.
• Password for Memcached admin user can be specified in the content of the file specified in MEMCACHED_PASSWORD_FILE.

1.5.0-r1

• The memcached container has been migrated to a non-root container approach. Previously the container run as root user and the memcached daemon was started as memcached user. From now own, both the container and the memcached daemon run as user 1001. As a consequence, the configuration files are writable by the user running the memcached process.

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) 2015-2020 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.