Prelaunch & Uplinks

Mothership fails fast: before a single ship launches, it verifies that external dependencies are reachable (uplinks) and runs your setup tasks (prelaunch jobs). If either fails, the launch aborts.

Execution order

1. Uplinks are verified (if configured)
2. Prelaunch jobs run in dependency order
3. Ships and bays launch

Uplinks

Uplinks are pre-flight connectivity checks for databases, caches, and services your fleet depends on:

[[mothership.uplinks]]
url = "postgres://localhost:5432/mydb"
name = "postgres"

[[mothership.uplinks]]
url = "$DATABASE_URL"   # env var expansion
name = "primary-db"
timeout = "10s"         # default: 5s

[[mothership.uplinks]]
url = "redis://cache.internal:6379"
name = "redis"

Supported schemes

Scheme	Default port	Check
postgres://, postgresql://	5432	TCP
mysql://	3306	TCP
redis://	6379	TCP
memgraph://, neo4j://	7687	TCP
http://, https://	80/443	HTTP GET
tcp://	required	TCP

Deduplication

Uplinks sharing the same host:port are checked only once:

# These share the same server — only one TCP check happens
[[mothership.uplinks]]
url = "postgres://localhost:5432/app_production"
name = "primary"

[[mothership.uplinks]]
url = "postgres://localhost:5432/app_replica"
name = "replica"

Checking uplinks from the CLI

mothership preflight   # validate manifest + verify uplinks (needs network access)
mothership clearance   # offline manifest validation only

preflight requires network access to the configured uplinks — running it on your laptop may fail if the uplinks are only reachable from the deployment environment.

Prelaunch jobs

Prelaunch jobs run setup tasks — migrations, cache warmup, schema initialization — before any ship or bay starts. All jobs must complete successfully or the launch is aborted.

[[mothership.prelaunch]]
name = "ar-migrate"
command = "rails"
args = ["db:migrate"]

[[mothership.prelaunch]]
name = "memgraph-migrate"
command = "./migrate-memgraph"
depends_on = ["ar-migrate"]  # runs after ar-migrate completes

Field	Type	Default	Description
name	string	required	Unique identifier
command	string	required	Command to execute
args	string[]	[]	Command arguments
env	table	{}	Environment variables
depends_on	string[]	[]	Other prelaunch jobs to wait for

If any prelaunch job exits non-zero, the entire launch is aborted.

Deploying the same manifest across multiple servers? Use Flagship so migrations run on exactly one instance.