docs/compose/startup-order.md

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How to control service startup and shutdown order in Docker Compose	documentation, docs, docker, compose, startup, shutdown, order	Control startup and shutdown order in Compose	true

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You can control the order of service startup and shutdown with the depends_on option. Compose always starts and stops containers in dependency order, where dependencies are determined by depends_on, links, volumes_from, and network_mode: "service:...".

A good example of when you might use this is an application which needs to access a database. If both services are started with docker compose up, there is a chance this will fail since the application service might start before the database service and won't find a database able to handle its SQL statements.

Control startup

On startup, Compose does not wait until a container is "ready", only until it's running. This can cause issues if, for example, you have a relational database system that needs to start its own services before being able to handle incoming connections.

The solution for detecting the ready state of a service is to use the condition attribute with one of the following options:

• service_started
• service_healthy. This specifies that a dependency is expected to be “healthy”, which is defined with healthcheck, before starting a dependent service.
• service_completed_successfully. This specifies that a dependency is expected to run to successful completion before starting a dependent service.

Reference information

• depends_on
• healthcheck