Wait for a referenced port

Before it starts instances, a deploy waits for the first deploy of each service whose port it references.

A variable of web has a reference to the port of api.

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These references need the port of another service. If that service is in its first deploy, the port has no value yet.

References to a port

${{service.NAME.port}}
${{service.NAME.hostport}}
${{service.NAME.internalUrl}}

The deploy waits only for services that are in their first deploy. See Env var references.

The build step

In the state building, the engine gets an image in one of three ways.

The service lock

The service lock lets one operation at a time change the containers of a service.