Docker Compose 1.21.0 已发布，获取地址：https://www.docker.com/products/docker

新版本带来了一些新特性，以及 bug 修复：

Compose file version 2.4

• Introduced version 2.4 of the docker-compose.yml specification.
  This version requires Docker Engine 17.12.0 or above.

• Added support for the platform parameter in service definitions.
  If supplied, the parameter is also used when performing build for the
  service.

Compose file version 2.2 and up

• Added support for the cpu_rt_period and cpu_rt_runtime parameters
  in service definitions (2.x only).

Compose file version 2.1 and up

• Added support for the cpu_period parameter in service definitions
  (2.x only).

• Added support for the isolation parameter in service build configurations.
  Additionally, the isolation parameter is used for builds as well if no
  build.isolation parameter is defined. (2.x only)

All formats

• Added support for the --workdir flag in docker-compose exec.

• Added support for the --compress flag in docker-compose build.

• docker-compose pull is now performed in parallel by default. You can
  opt out using the --no-parallel flag. The --parallel flag is now
  deprecated and will be removed in a future version.

• Dashes and underscores in project names are no longer stripped out.

• docker-compose build now supports the use of Dockerfile from outside
  the build context.

Bugfixes

• Compose now checks that the volume's configuration matches the remote
  volume, and errors out if a mismatch is detected.

• Fixed a bug that caused Compose to raise unexpected errors when attempting
  to create several one-off containers in parallel.

• Fixed a bug with argument parsing when using docker-machine config to
  generate TLS flags for exec and run commands.

• Fixed a bug where variable substitution with an empty default value
  (e.g. ${VAR:-}) would print an incorrect warning.

• Improved resilience when encoding of the Compose file doesn't match the
  system's. Users are encouraged to use UTF-8 when possible.

• Fixed a bug where external overlay networks in Swarm would be incorrectly
  recognized as inexistent by Compose, interrupting otherwise valid
  operations.

源码下载和发布说明：https://github.com/docker/compose/releases/tag/1.21.0