Ephemeral Services

import VideoPlayer from '@components/VideoPlayer';

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

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).

Use cases

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

Service containers

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.

Example

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

See it in action:

<VideoPlayer src="/img/current_docs/introduction/features/service-container.webm" alt="Container to host networking" />

Host services

This also works in the opposite direction: containers in Dagger Functions can communicate with services running on the host.

Example

Here's an example of how a workflow running in a Dagger Function can access and query a MariaDB database service running on the host:

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

See it in action:

<VideoPlayer src="/img/current_docs/introduction/features/service-host.webm" alt="Host to container networking" />

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]