Skip to main content

Release channels

A release channel is a graph of releases associated with zero to many cohorts that specify the possible update paths devices within associated cohorts can traverse.

bundle distribution

For information about how release channels participate in resolving target bundles for devices, see the bundle distribution reference.

Graph details​

A release channel forms a anti-arborescence graph. In other words, releases may point to exactly one next release, a release may be pointed to by zero to many releases, and all releases eventually converge to a single release that points to no node.

When reasoning about releases as nodes in such a graph, there are three categories of nodes:

  • source nodes - Nodes that no other nodes point to.
  • intermediate nodes - Nodes that are pointed to, and that point to other nodes.
  • sink nodes - Nodes that are pointed to, but point to no other nodes.
latest release

In conversation, the sink node is often referred to as the latest release.

Rules​

zero-to-one-sinks​

There can only ever be at most a single latest release at any given time. Or in graph terms, an anti-arborescence graph is either empty, or has at most a single sink node.

only-sinks-constrain-availability​

The latest release of a graph is special in that it is the only release within a graph that is allowed to constrain its availability.

latest release creation pre-requisites

This rule has the side effect of requiring the current latest release, should it exist, to have its availability unconstrained before a new latest release can be created.

unconstrained-sink-before-new-sink​

You cannot create a new latest release while the current latest release has constrained availability.

Example​

Consider the following release channel:

Figure 1​

R4-------->R5---\
                 \
R1---\            |--->R6
      |--->R2----/
R3---/
  • source nodes - R4, R1, and R3.
  • intermediate nodes - R5 and R2.
  • sink nodes - R6.

Or a more linear variation:

Figure 2​

R1--->R2--->R3--->R4--->R5--->R6
  • source nodes - R1.
  • intermediate nodes - R2-5.
  • sink nodes - R6.

In both figure 1 and figure 2 the latest release is the sink node R6.