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A provider's resource lives outside the compose network: consumers could
only reach it through injected variables carrying a host-published
address — nothing like the compose-native experience of addressing a
service by name at its well-known port.
A provider may now publish where each endpoint of its resource actually
listens:
{"type": "publish-endpoint", "message": "80=localhost:49152"}
The endpoint is announced as seen from the provider's host: the relay —
the component that knows it runs inside a container — rewrites loopback
or unspecified upstream hosts to host.docker.internal (resolved through
its injected host-gateway extra_host); routable addresses pass through.
When at least one endpoint is published, compose deploys a relay
container in place of the service: a minimal TCP forwarder (new relay/
directory, published as docker/compose-relay, overridable with
COMPOSE_RELAY_IMAGE for internal registries) joining the networks of the
services that depend on the provider service, aliased with the service
name. Consumers then use http://<service>:<port> as if the service were
a regular container.
The relay is a first-class project container — canonical name, standard
compose labels including config-hash (label-driven commands run without
the compose file keep seeing the service: ps, logs, stop, down) — plus
the com.docker.compose.relay label declaring its role:
- the reconciler already leaves provider services' containers alone, and
the relay's identity hash (image + routes) makes up idempotent: kept
when routes are unchanged, recreated otherwise;
- process-level commands (exec, cp) refuse a relay — there is no service
process in it to act on;
- the up monitor excludes relays from the containers whose termination
ends an attached up: they are long-lived infrastructure and would
otherwise keep 'up' waiting forever.
The example provider demonstrates the flow behind PROVIDER_DEMO_ENDPOINT
(a detached helper serving a fixed HTTP response), backed by an e2e
scenario asserting the compose-native address works and exec is refused.
Signed-off-by: Nicolas De Loof <nicolas.deloof@gmail.com>
3 lines
48 B
Modula-2
3 lines
48 B
Modula-2
module github.com/docker/compose-relay
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go 1.23
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