Supported tags and respective
Where to file issues:
the Docker Community
Supported Docker versions:
the latest release (down to 1.6 on a best-effort basis)
What is Memcached?
Memcached is a general-purpose distributed memory caching system. It is often used to speed up dynamic database-driven websites by caching data and objects in RAM to reduce the number of times an external data source (such as a database or API) must be read.
Memcached's APIs provide a very large hash table distributed across multiple machines. When the table is full, subsequent inserts cause older data to be purged in least recently used order. Applications using Memcached typically layer requests and additions into RAM before falling back on a slower backing store, such as a database.
How to use this image
$ docker run --name my-memcache -d memcached
Start your memcached container with the above command and then you can connect you app to it with standard linking:
$ docker run --link my-memcache:memcache -d my-app-image
The memcached server information would then be available through the ENV variables generated by the link as well as through DNS as
How to set the memory usage for memcached
$ docker run --name my-memcache -d memcached memcached -m 64
This would set the memcache server to use 64 megabytes for storage.
For infomation on configuring your memcached server, see the extensive wiki.
memcached images come in many flavors, each designed for a specific use case.
This is the defacto image. If you are unsure about what your needs are, you probably want to use this one. It is designed to be used both as a throw away container (mount your source code and start the container to start your app), as well as the base to build other images off of.
This image is based on the popular Alpine Linux project, available in the
alpine official image. Alpine Linux is much smaller than most distribution base images (~5MB), and thus leads to much slimmer images in general.
This variant is highly recommended when final image size being as small as possible is desired. The main caveat to note is that it does use musl libc instead of glibc and friends, so certain software might run into issues depending on the depth of their libc requirements. However, most software doesn't have an issue with this, so this variant is usually a very safe choice. See this Hacker News comment thread for more discussion of the issues that might arise and some pro/con comparisons of using Alpine-based images.
To minimize image size, it's uncommon for additional related tools (such as
bash) to be included in Alpine-based images. Using this image as a base, add the things you need in your own Dockerfile (see the
alpine image description for examples of how to install packages if you are unfamiliar).
View license information for the software contained in this image.
The 1.4.38-alpine and 1.4.39-alpine image seem to segfault on startup when run with -o lru_maintainer (or -o modern). I... don't know enough about debugging this stuff in docker -- spent a nontrivial amount of time trying to just get a core dump out of the exe (and failing). But figured this information might be useful to someone. My workaround has been to just switch to 1.4.39 (non-alpine)
mem_limit in Docker Compose is not necessary. We can just rely on memcached to control the limit itself. Docker memory limit is useful when the content is not trusted (like running commands from users).
This usage in Docker Compose seems to work -- can anyone clarify if this is the intended usage?
# 1 GB Memcached Container memcached: image: memcached ports: - "127.0.0.1:11211:11211" mem_limit: 1g command: memcached -m 1024m
Is it possible to set memory using ENV variable? As far as I can see it in source it's not possible?
Can someone post a example docker-compose for this official memcached usage with php/nginx ..etc ? i,e with some possible parameters like set memory ..etc
I set the option -m 2g when I start the docker. but when I add some key-value , the memory cannot be used more than 70M (I get it in with the cadvisor ). Asking for help!
How do I run multiple memcached Docker containers across multiple machines to form a single cluster?