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Docker 1.6 Emerges As A Platform

Several components of Docker, including Engine, Registry, and orchestration tools, have been upgraded together as a platform.
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The Docker container formatting system, with its varied tools, is being pulled together into a more uniform platform for container management, with the issuance of Release 1.6 on April 16.

As a result, its emphasis is shifting from container construction for developers to container management for operations. Performance is important to developers, but it's even more important in production settings, where certain actions are going to be repeated thousands of times.

The Docker Engine now has a different protocol for interacting with the Docker Registry when a container image is sought for launch.

In the past, a "pull" request would lead to the container image's operating system layer being downloaded, followed by needed libraries, application logic, database connections, and related dependencies, in a sequential process. Now that process can take place with the layers downloaded in parallel, simultaneously, then shuffled into correct image order at the destination.

That's thanks to the "complete rewrite" of the Registry for the 2.0 version, along with a new Registry API. The upgraded Docker Engine 1.6 works with the Registry 2.0 API.

In addition, the new API allows more granularity to Docker images, with each layer given a unique identifier. If one layer only needs to be updated, that layer can be accessed in the Hub and downloaded, although all the layers in the stack that come after it will need to be downloaded as well, explained Scott Johnston, senior vice president of product at Docker.

[Read about Docker's recent additions.]

The process can speed a container image update. "You just update those layers that need it." The way containers are formatted is to put down layers, so that any successive layer meets any dependencies in the layers below it. Once a layer is updated, the layers above it must be updated as well, in case any of the operations above it have changed as a result of that change.

In an interview, Johnston said there have been 300 million downloads of Docker container images from the DockerHub since it was launched in beta in April 2014. The images represent containerized applications that someone needs in his or her data center.

Speeding up those downloads will make Docker more useful in production settings.

Part of what's driving the activity is the ability to access previously used components at Docker Hub Official Repos, which include basic services such as specific Linux distributions, databases, and applications servers, already available in a container.

Johnston said before the announcement that he expected figures reflecting how much faster the downloads would be to be posted in a blog on the Docker Engine 1.6 announcement. The blog, once posted Thursday, only cited "dramatically faster" downloads.

Docker Engine 1.6 is "backward compatible" with previous versions of the API so that existing Docker systems don't need to be modified, Johnston noted.

In Thursday's launch of the second Docker Compose tool, Release 1.2, has been revised to make it possible to define and run multi-container applications, with the containers sometimes operating in separate environments but still linked. Compose "makes it easy to share configurations between different environments" and use one configuration for development and test and another for production.

Additional changes in the 1.6 release of Docker are referenced in the April 16 blog.

In the past, Docker has risked splintering its approach to its customers by introducing container formatting, orchestration, and cluster management products in rapid-fire succession, with various user interactions and interfaces. From this point forward, it is consolidating announcements into a single event, upgrading Docker Engine, Registry, Compose, Machine, and Swarm at the same time "for a more consistent user experience."

"By synchronizing our releases, we are simplifying the evaluation and deployment process and enabling the community to benefit from the integrated value that we're building for them," said Solomon Hykes, CTO and chief architect of Docker.

At two-years-old, Docker is trying to become a mature software company.

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