Make swarm.init() and network.create() idempotent

Catch APIError on swarm.init() for already-in-swarm case. Check
existing networks before creating superset-network. Re-runs after
partial failure no longer fail on these operations.

Closes #50

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: szachovy

CHANGELOG.md

@@ -16,6 +16,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * CI workflow to build and push service images to GitHub Container Registry on master merge. (#97)
 * Pull-first with local build fallback for container images during deployment. (#97)
 
+### Fixed
+
+* Make swarm.init() and network.create() idempotent for re-run support. (#50)
+
 ### Changed
 
 * Completed [ARCHITECTURE.md](./docs/ARCHITECTURE.md) (#93)

src/container.py

@@ -384,10 +384,15 @@ def __init__(self, client: docker.client.DockerClient, virtual_ip_address: str)
                 self.healthcheck_retries = 5
 
             def initialize_swarm(self) -> None:
-                self.client.swarm.init(advertise_addr=self.virtual_ip_address)
+                try:
+                    self.client.swarm.init(advertise_addr=self.virtual_ip_address)
+                except docker.errors.APIError:
+                    pass  # Already in a swarm
 
             def create_network(self) -> None:
-                self.client.networks.create(name='superset-network', driver='overlay', attachable=True)
+                existing = self.client.networks.list(names=['superset-network'])
+                if not existing:
+                    self.client.networks.create(name='superset-network', driver='overlay', attachable=True)
 
             def run(self) -> None:
                 self.initialize_swarm()