1.2.6 Docker 1.12

The focus of this release was to simplify and improve container orchestration, providing facilities such as load-balancing, service discovery, high availability and scalability out of the box. Features to handle multi-host and multi-container orchestration have been built right into the Docker Engine to allow administrators to deploy and manage applications on a group of Docker Engines called a swarm. Docker swarm mode provides much of the functionality included in the original standalone Docker Swarm service that ran separately to the Docker Engine itself and includes additional features such as built-in load-balancing. By integrating this technology into the Docker Engine, deployment of a high availability clustering technology is simplified and these features are unified within a single API and CLI. All communications within the Docker swarm are encrypted using Transport Layer Security (TLS) and cluster nodes are protected using cryptographic node fingerprint key technology to prevent node spoofing.

Important

The Docker Swarm functionality is released as a technology preview for Oracle Linux. As a technology preview, this feature is still under development but is made available for testing and evaluation purposes.

The Docker Engine has been rearchitected to run on top of a combination of the docker-containerd and docker-runc binaries. While this change is transparent and docker commands continue to work as they did in previous releases, the underlying technology further modularizes the Docker architecture in line with the Open Container Initiative (OCI) specification. These changes open up new possibilities for container execution backends and container management, including the potential to perform engine restarts and upgrades without the need to restart running containers.

Other notable changes in this version of the Docker Engine are:

  • Experimental support for the MacVlan and IPVLAN network drivers to take advantage of existing VLAN networking infrastructure

  • Support for AAAA Records (aka IPv6 Service Discovery) in embedded DNS Server, which allows for IPv6 queries to be resolved locally without being forwarded to external servers

  • Multiple A/AAAA records from embedded DNS Server for DNS Round robin to facilitate load-balancing between containers.

  • Source the forwarded DNS queries from the container net namespace

  • Better handling of low disk space to allow the device mapper to fail more gracefully in the case where there is insufficient disk space.