uniac.yaml is the entrypoint for an application composition. It describes
one or more named resources in YAML: reusable service definitions and the
deployment declarations that instantiate them. YAML is the currently
supported composition format.
File format
The document is a mapping with these top-level fields:
Resource names match
^[a-z0-9]+(?:(?:__?|-+)[a-z0-9]+)*$ and are unique
within the file. Every resource requires type; unknown fields are rejected
at every level.
Definitions and service instances
type: service and type: singleton create reusable service definitions
for stateless and singleton execution. A definition holds the OCI image or
Dockerfile build source, environment, startup command, and storage needs.
Declaring it alone creates no remote service. Complete field contracts are
in Service and Volume.
A type: deployment resource instantiates definitions: its services
mapping gives each instance a service name and a definition to instantiate.
The selected declaration contributes its named instances to the deployment
description; unreferenced definitions and other deployment declarations in
the file are not included.
The service instance is the named remote service, not an individual
container replica. Multiple instances can reuse one definition. The
definition’s name is a local label; the instance name supplies the service’s
identity in the target project. An instance name is one DNS label: lowercase
letters, digits and dashes, starting and ending with a letter or digit, at
most 63 characters.
Only a deployment declaration is a selectable target. It creates no remote
service group or environment; each resulting service has its own
deployment versions.
The target project’s identity is supplied separately from this file.
Example composition
This application has an API and a private Redis service with durable storage. It assumesapi/Dockerfile builds an application listening on port 8080 that
uses CACHE_URL to connect to Redis.
api-deployment instantiates api_definition as the service api;
cache-deployment instantiates cache_definition as cache. Selecting
api-deployment includes only api in the deployment description. Its
reference to cache does not instantiate that service; cache-deployment
is a separate target.
The reference names the cache instance, and that instance gives its volume
the project-scoped name cache.data. The API is publicly exposed; Redis is
reachable within the project’s private network.
Environment and references explains
resolution between services, including services outside a selected
declaration.
Validation
Local validation checks the whole file’s schema, resource names, individual service declarations,from references, and default target. Composition of
the selected declaration additionally checks instance names, build-source
paths on disk, composed volume names, referenced variables within that
declaration, and reference cycles.
Generated description
The generated description is JSON withkind: deployable and a services
array. Each entry contains an instance name, normalized source declaration,
environment templates, and runtime configuration. It contains no remote
project binding, and environment values remain templates until deployment.
The digest identifies that description. Equivalent path spellings, omitted
build defaults, YAML formatting, and mapping or exposure-list ordering do not
change it. An explicit build target remains part of the description even
when it names the Dockerfile’s last stage. The digest excludes source-file
and image contents and remotely resolved environment values.