import Tabs from '@theme/Tabs'; import TabItem from '@theme/TabItem';

Ephemeral Services

Dagger Functions support service containers, enabling users to spin up additional services (as containers) and communicate with those services from their pipelines.

This makes it possible to:

• Instantiate and return services from a Dagger Function, and then:
  • Use those services in other Dagger Functions (container-to-container networking)
  • Use those services from the calling host (container-to-host networking)
• Expose host services for use in a Dagger Function (host-to-container networking).

Services instantiated by a Dagger Function run in service containers, which have the following characteristics:

• Each service container has a canonical, content-addressed hostname and an optional set of exposed ports.
• Service containers are started just-in-time, de-duplicated, and stopped when no longer needed.
• Service containers are health checked prior to running clients.

Some common scenarios for using services with Dagger Functions are:

• Running a database service for local storage or testing
• Running end-to-end integration tests against a service
• Running sidecar services

Here is an example of a Dagger Function that returns an HTTP service, which can then be accessed from the calling host:

<Tabs groupId="language"> <TabItem value="Go"> ```go file=./snippets/services-1/go/main.go ``` </TabItem> <TabItem value="Python"> ```python file=./snippets/services-1/python/main.py ``` </TabItem> <TabItem value="TypeScript"> ```typescript file=./snippets/services-1/typescript/index.ts ``` </TabItem> <TabItem value="PHP"> ```php file=./snippets/services-1/php/src/MyModule.php ``` </TabItem> <TabItem value="Java"> ```java file=./snippets/services-1/java/src/main/java/io/dagger/modules/mymodule/MyModule.java ``` </TabItem> </Tabs>

See it in action:

This also works in the opposite direction: containers in Dagger Functions can communicate with services running on the host. Here's an example of how a pipeline running in a Dagger Function can access and query a MariaDB database service running on the host:

<Tabs groupId="language"> <TabItem value="Go"> ```go file=./snippets/services-2/go/main.go ``` </TabItem> <TabItem value="Python"> ```python file=./snippets/services-2/python/main.py ``` </TabItem> <TabItem value="TypeScript"> ```typescript file=./snippets/services-2/typescript/index.ts ``` </TabItem> <TabItem value="PHP"> ```php file=./snippets/services-2/php/src/MyModule.php ``` </TabItem> <TabItem value="Java"> ```java file=./snippets/services-2/java/src/main/java/io/dagger/modules/mymodule/MyModule.java ``` </TabItem> </Tabs>

See it in action:

Learn more

• Use services as function arguments
• Create and return services from a function
• Expose host services to a function
• Start and stop services
• Persist service state