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Service References

devhost supports late-binding/runtime service references using {{ services.<name>.<property> }} placeholders. This allows services to dynamically discover configuration from other services in the stack (such as auto-allocated ports or bind hosts) right before they are launched.

This is particularly useful in multi-service monorepos where databases or backend services run on dynamically allocated ports (port = "auto"), and consuming services need to discover those ports to establish a network connection.

Placeholders

Section titled “Placeholders”

This applies to:

  • String fields in service command arrays
  • Values in service env maps

Supported properties

Section titled “Supported properties”
  • port
    • The resolved port number of the target service (e.g., {{ services.postgres.port }}).
    • If the referenced service does not have a port configured, devhost will raise a resolution error at startup.
  • host
    • The configured routing host of the target service, falling back to its bind host if no custom host is defined.
  • bindHost
    • The direct bind host of the target service.

Example

Section titled “Example”
[services.postgres]
bindHost = "127.0.0.1"
port = "auto"


[services.poc-backend]
command = ["node", "server.js"]
health = { tcp = 8080 }
env = { DATABASE_URL = "postgres://postgres:postgres@{{ services.postgres.bindHost }}:{{ services.postgres.port }}/postgres?sslmode=disable" }

In this example, both the bindHost and the dynamic port of the postgres database service are automatically resolved and injected into the backend’s DATABASE_URL environment variable at startup, with zero manual coordination or hardcoded ports.