Template variables

The values in env:, databases:, services.<name>.cmd, and a handful of other fields are templates. Pomelo resolves them when materializing each workspace, substituting values from the network state, shared services, other services, and the workspace's branch.

Templates use dot-notation: {{ <source>.<name>[.<field>] }}. Every reference is validated at load — a typo, a renamed alias, or a missing database name fails loudly with a clear error instead of breaking silently at runtime.

Catalog

Template	Resolves to	Example
{{shared.<name>.url}}	Shared service conn user:pass@host:port	postgres:postgres@localhost:44800
{{shared.<name>.host}}	Shared service host (always localhost on the host)	localhost
{{shared.<name>.port}}	Shared service port	44800
{{shared.<name>.user}} / .pass	Shared service credentials	postgres
{{shared.<name>.slot}}	Capacity slot index (e.g. Redis DB number)	3
{{db.<name>}}	Named database (session-prefixed, branch-resolved)	myproject_feat_login
{{db.<name>.url}}	Full postgres://…/<db> URL via the shared postgres	postgres://…:44800/myproject_feat_login
{{<repo>.<service>.url}}	A service's base URL (profile-aware)	http://api.api.feat-login.localhost:41000
{{<repo>.<service>.path}}	Same-origin dev-proxy path	/_pom_dev/api/api
{{<repo>.<service>.host}} / .port / .ws	Service host / port / ws URL	…
{{secret.<NAME>}}	Value from the secrets store	sk_live_…
{{slot.<name>}}	Allocated slot index for capacity-limited services	3
{{branch.safe}}	Branch with /→_, -→_ (safe for DB names)	feat_login
{{branch.host}}	Branch as a DNS label (a-z0-9-)	feat-login
{{branch.hash}}	Short stable hash of the branch	a1b2c3
{{bind_ip}}	Service bind address — always 127.0.0.1	127.0.0.1

Shared services: {{shared.<name>.*}}

Wire every declared shared service into the repos that use it. A shared service you declare but never reference is flagged by pom (the config doctor calls it unwired) — its container starts but nothing connects.

shared_services:
  postgres: {}     # well-known defaults fill image/port/creds
  redis: {}
  opensearch: {}
env:
  DATABASE_URL:  postgresql://{{shared.postgres.url}}/{{db.main}}?schema=public
  REDIS_URL:     redis://{{shared.redis.host}}:{{shared.redis.port}}/{{shared.redis.slot}}
  OPENSEARCH_URL: http://{{shared.opensearch.host}}:{{shared.opensearch.port}}

Named databases: {{db.<name>}}

Databases are a named map, referenced by name — never by position:

databases:
  main: {}
  test: {}
env:
  DATABASE_URL: "postgresql://{{shared.postgres.url}}/{{db.main}}"

Cross-service URLs: {{<repo>.<service>.url}}

Reference another repo's service by its alias and service name. The .url form is profile-aware — an environments:<profile> override retargets it to a remote host; on local it points at the dev-proxy. The .path form is always the same-origin route (/_pom_dev/<repo>/<service>), so a frontend can call the backend without CORS.

env:
  WORKER_URL: '{{worker.api.url}}'          # the `api` service of the `worker` repo
  NEXT_PUBLIC_API_URL: '{{web.app.url}}/_pom_dev/api/api'

Switchable variables: {{var:NAME}}

A service can also publish a named variable with exposes; consumers use {{var:NAME}} and an environments:<profile> entry overrides it. Prefer the dot service-ref above for a plain cross-service URL; use {{var:}} for free/published variables.

services:
  web:
    cmd: bundle exec puma -p $PORT
    port: true
    exposes: API_URL          # API_URL = this service's local URL
env:
  API_HOST: "{{var:API_URL}}"
  API_WS:   "{{var:API_URL | ws}}"   # http→ws / https→wss
environments:
  staging:
    API_URL: "https://api.acme.dev"  # override under the staging profile

Where they work

• repos.<repo>.env (flat, file-keyed, or "*" shared base)
• repos.<repo>.databases
• repos.<repo>.services.<svc>.env
• shared_services.<svc>.environment
• environments.<profile>.* (variable override values)

Anywhere else, templates are left untouched.

Resolving example

Given a workspace on branch feat/login and session: myproject:

databases:
  main: {}
env:
  DATABASE_URL: "postgresql://{{shared.postgres.url}}/{{db.main}}"
  REDIS_URL: "redis://{{shared.redis.host}}:{{shared.redis.port}}/{{shared.redis.slot}}"

becomes

DATABASE_URL=postgresql://postgres:postgres@localhost:44800/myproject_feat_login
REDIS_URL=redis://localhost:44801/3

Legacy forms

The colon forms still resolve for back-compat but have dot replacements — prefer the dot form:

Legacy	Write instead
{{conn:name}}	{{shared.name.url}}
{{host:name}} / {{port:name}}	{{shared.name.host}} / {{shared.name.port}}
{{db:name}}	{{db.name}}
{{slot:name}}	{{slot.name}}
{{branch_safe}} / {{branch_host}}	{{branch.safe}} / {{branch.host}}

Removed entirely in v2: {{url:}} / {{ws:}} string templates, positional {{db:N}}, global_services, the per-repo env_switch bool.