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Builds

This page contains practical examples for building artifacts (files and directories) with Dagger. Each section below provides code examples in multiple languages and demonstrates different approaches to building artifacts.

Perform a multi-stage build​

The following Dagger Function performs a multi-stage build.

package main

import (
	"context"

	"dagger/my-module/internal/dagger"
)

type MyModule struct{}

// Build and publish Docker container
func (m *MyModule) Build(
	ctx context.Context,
	// source code location
	// can be local directory or remote Git repository
	src *dagger.Directory,
) (string, error) {
	// build app
	builder := dag.Container().
		From("golang:latest").
		WithDirectory("/src", src).
		WithWorkdir("/src").
		WithEnvVariable("CGO_ENABLED", "0").
		WithExec([]string{"go", "build", "-o", "myapp"})

	// publish binary on alpine base
	prodImage := dag.Container().
		From("alpine").
		WithFile("/bin/myapp", builder.File("/src/myapp")).
		WithEntrypoint([]string{"/bin/myapp"})

	// publish to ttl.sh registry
	addr, err := prodImage.Publish(ctx, "ttl.sh/myapp:latest")
	if err != nil {
		return "", err
	}

	return addr, nil
}

Example​

Perform a multi-stage build of the source code in the golang/example/hello repository and publish the resulting image:

dagger -c 'build https://github.com/golang/example#master:hello'

Perform a matrix build​

The following Dagger Function performs a matrix build.

package main

import (
	"context"
	"dagger/my-module/internal/dagger"
	"fmt"
)

type MyModule struct{}

// Build and return directory of go binaries
func (m *MyModule) Build(
	ctx context.Context,
	// Source code location
	src *dagger.Directory,
) *dagger.Directory {
	// define build matrix
	gooses := []string{"linux", "darwin"}
	goarches := []string{"amd64", "arm64"}

	// create empty directory to put build artifacts
	outputs := dag.Directory()

	golang := dag.Container().
		From("golang:latest").
		WithDirectory("/src", src).
		WithWorkdir("/src")

	for _, goos := range gooses {
		for _, goarch := range goarches {
			// create directory for each OS and architecture
			path := fmt.Sprintf("build/%s/%s/", goos, goarch)

			// build artifact
			build := golang.
				WithEnvVariable("GOOS", goos).
				WithEnvVariable("GOARCH", goarch).
				WithExec([]string{"go", "build", "-o", path})

			// add build to outputs
			outputs = outputs.WithDirectory(path, build.Directory(path))
		}
	}

	// return build directory
	return outputs
}

Example​

Perform a matrix build of the source code in the golang/example/hello repository and export build directory with go binaries for different operating systems and architectures.

dagger -c 'build https://github.com/golang/example#master:hello | export /tmp/matrix-builds'

Inspect the contents of the exported directory with tree /tmp/matrix-builds. The output should look like this:

/tmp/matrix-builds
└── build
    ├── darwin
    │   ├── amd64
    │   │   └── hello
    │   └── arm64
    │       └── hello
    └── linux
        ├── amd64
        │   └── hello
        └── arm64
            └── hello

8 directories, 4 files

Build multi-arch image​

The following Dagger Function builds a single image for different CPU architectures using native emulation.

package main

import (
	"context"

	"dagger/my-module/internal/dagger"
)

type MyModule struct{}

// Build and publish multi-platform image
func (m *MyModule) Build(
	ctx context.Context,
	// Source code location
	// can be local directory or remote Git repository
	src *dagger.Directory,
) (string, error) {
	// platforms to build for and push in a multi-platform image
	var platforms = []dagger.Platform{
		"linux/amd64", // a.k.a. x86_64
		"linux/arm64", // a.k.a. aarch64
		"linux/s390x", // a.k.a. IBM S/390
	}

	// container registry for the multi-platform image
	const imageRepo = "ttl.sh/myapp:latest"

	platformVariants := make([]*dagger.Container, 0, len(platforms))
	for _, platform := range platforms {
		// pull golang image for this platform
		ctr := dag.Container(dagger.ContainerOpts{Platform: platform}).
			From("golang:1.20-alpine").
			// mount source code
			WithDirectory("/src", src).
			// mount empty dir where built binary will live
			WithDirectory("/output", dag.Directory()).
			// ensure binary will be statically linked and thus executable
			// in the final image
			WithEnvVariable("CGO_ENABLED", "0").
			// build binary and put result at mounted output directory
			WithWorkdir("/src").
			WithExec([]string{"go", "build", "-o", "/output/hello"})

		// select output directory
		outputDir := ctr.Directory("/output")

		// wrap the output directory in the new empty container marked
		// with the same platform
		binaryCtr := dag.Container(dagger.ContainerOpts{Platform: platform}).
			WithRootfs(outputDir)

		platformVariants = append(platformVariants, binaryCtr)
	}

	// publish to registry
	imageDigest, err := dag.Container().
		Publish(ctx, imageRepo, dagger.ContainerPublishOpts{
			PlatformVariants: platformVariants,
		})

	if err != nil {
		return "", err
	}

	// return build directory
	return imageDigest, nil
}

Example​

Build and publish a multi-platform image:

dagger -c 'build https://github.com/golang/example#master:hello'

Build multi-arch image with cross-compliation​

The following Dagger Function builds a single image for different CPU architectures using cross-compilation.

info

This Dagger Function uses the containerd utility module. To run it locally install the module first with dagger install github.com/levlaz/daggerverse/containerd@v0.1.2

package main

import (
	"context"

	"dagger/my-module/internal/dagger"
)

type MyModule struct{}

// Build and publish multi-platform image
func (m *MyModule) Build(
	ctx context.Context,
	// Source code location
	// can be local directory or remote Git repository
	src *dagger.Directory,
) (string, error) {
	// platforms to build for and push in a multi-platform image
	var platforms = []dagger.Platform{
		"linux/amd64", // a.k.a. x86_64
		"linux/arm64", // a.k.a. aarch64
		"linux/s390x", // a.k.a. IBM S/390
	}

	// container registry for the multi-platform image
	const imageRepo = "ttl.sh/myapp:latest"

	platformVariants := make([]*dagger.Container, 0, len(platforms))
	for _, platform := range platforms {
		// parse architecture using containerd utility module
		platformArch, err := dag.Containerd().ArchitectureOf(ctx, platform)

		if err != nil {
			return "", err
		}

		// pull golang image for the *host* platform, this is done by
		// not specifying the a platform. The default is the host platform.
		ctr := dag.Container().
			From("golang:1.21-alpine").
			// mount source code
			WithDirectory("/src", src).
			// mount empty dir where built binary will live
			WithDirectory("/output", dag.Directory()).
			// ensure binary will be statically linked and thus executable
			// in the final image
			WithEnvVariable("CGO_ENABLED", "0").
			// configure go compiler to use cross-compilation targeting the
			// desired platform
			WithEnvVariable("GOOS", "linux").
			WithEnvVariable("GOARCH", platformArch).
			// build binary and put result at mounted output directory
			WithWorkdir("/src").
			WithExec([]string{"go", "build", "-o", "/output/hello"})

		// select output directory
		outputDir := ctr.Directory("/output")

		// wrap the output directory in the new empty container marked
		// with the same platform
		binaryCtr := dag.Container(dagger.ContainerOpts{Platform: platform}).
			WithRootfs(outputDir).
			WithEntrypoint([]string{"/hello"})

		platformVariants = append(platformVariants, binaryCtr)
	}

	// publish to registry
	imageDigest, err := dag.Container().
		Publish(ctx, imageRepo, dagger.ContainerPublishOpts{
			PlatformVariants: platformVariants,
		})

	if err != nil {
		return "", err
	}

	// return build directory
	return imageDigest, nil
}

Example​

Build and publish a multi-platform image with cross compliation:

dagger -c 'build https://github.com/golang/example#master:hello'

Build image from Dockerfile​

The following Dagger Function builds an image from a Dockerfile.

package main

import (
	"context"

	"dagger/my-module/internal/dagger"
)

type MyModule struct{}

// Build and publish image from existing Dockerfile
func (m *MyModule) Build(
	ctx context.Context,
	// location of directory containing Dockerfile
	src *dagger.Directory,
) (string, error) {
	ref, err := src.
		DockerBuild(). // build from Dockerfile
		Publish(ctx, "ttl.sh/hello-dagger")

	if err != nil {
		return "", err
	}

	return ref, nil
}

Example​

Build and publish an image from an existing Dockerfile

dagger -c 'build https://github.com/dockersamples/python-flask-redis'

Build image from Dockerfile using different build context​

The following function builds an image from a Dockerfile with a build context that is different than the current working directory.

package main

import (
	"context"
	"dagger/my-module/internal/dagger"
)

type MyModule struct{}

// Build and publish image from Dockerfile using a build context directory
// in a different location than the current working directory
func (m *MyModule) Build(
	ctx context.Context,
	// location of source directory
	src *dagger.Directory,
	// location of Dockerfile
	dockerfile *dagger.File,
) (string, error) {

	// get build context with dockerfile added
	workspace := dag.Container().
		WithDirectory("/src", src).
		WithWorkdir("/src").
		WithFile("/src/custom.Dockerfile", dockerfile).
		Directory("/src")

	// build using Dockerfile and publish to registry
	ref, err := dag.Container().
		Build(workspace, dagger.ContainerBuildOpts{
			Dockerfile: "custom.Dockerfile",
		}).
		Publish(ctx, "ttl.sh/hello-dagger")

	if err != nil {
		return "", err
	}

	return ref, nil
}

Example​

Build an image from the source code in https://github.com/dockersamples/python-flask-redis using the Dockerfile from a different build context, at https://github.com/vimagick/dockerfiles#master:registry-cli/Dockerfile:

dagger -c 'build https://github.com/dockersamples/python-flask-redis https://github.com/vimagick/dockerfiles#master:registry-cli/Dockerfile'

Cache application dependencies​

The following Dagger Function uses a cache volume for application dependencies. This enables Dagger to reuse the contents of the cache across Dagger Function runs and reduce execution time.

package main

import "dagger/my-module/internal/dagger"

type MyModule struct{}

// Build an application using cached dependencies
func (m *MyModule) Build(
	// Source code location
	source *dagger.Directory,
) *dagger.Container {
	return dag.Container().
		From("golang:1.21").
		WithDirectory("/src", source).
		WithWorkdir("/src").
		WithMountedCache("/go/pkg/mod", dag.CacheVolume("go-mod-121")).
		WithEnvVariable("GOMODCACHE", "/go/pkg/mod").
		WithMountedCache("/go/build-cache", dag.CacheVolume("go-build-121")).
		WithEnvVariable("GOCACHE", "/go/build-cache").
		WithExec([]string{"go", "build"})
}

Example​

Build an application using cached dependencies:

dagger -c 'build .'

Execute functions concurrently​

The following Dagger Function demonstrates how to use native-language concurrency features (errgroups in Go, task groups in Python), and promises in TypeScript to execute other Dagger Functions concurrently. If any of the concurrently-running functions fails, the remaining ones will be immediately cancelled.

package main

import (
	"context"

	"dagger/my-module/internal/dagger"

	"golang.org/x/sync/errgroup"
)

// Constructor
func New(
	source *dagger.Directory,
) *MyModule {
	return &MyModule{
		Source: source,
	}
}

type MyModule struct {
	Source *dagger.Directory
}

// Return the result of running unit tests
func (m *MyModule) Test(ctx context.Context) (string, error) {
	return m.BuildEnv().
		WithExec([]string{"npm", "run", "test:unit", "run"}).
		Stdout(ctx)
}

// Return the result of running the linter
func (m *MyModule) Lint(ctx context.Context) (string, error) {
	return m.BuildEnv().
		WithExec([]string{"npm", "run", "lint"}).
		Stdout(ctx)
}

// Return the result of running the type-checker
func (m *MyModule) Typecheck(ctx context.Context) (string, error) {
	return m.BuildEnv().
		WithExec([]string{"npm", "run", "type-check"}).
		Stdout(ctx)
}

// Run linter, type-checker, unit tests concurrently
func (m *MyModule) RunAllTests(ctx context.Context) error {
	// Create error group
	eg, gctx := errgroup.WithContext(ctx)

	// Run linter
	eg.Go(func() error {
		_, err := m.Lint(gctx)
		return err
	})

	// Run type-checker
	eg.Go(func() error {
		_, err := m.Typecheck(gctx)
		return err
	})

	// Run unit tests
	eg.Go(func() error {
		_, err := m.Test(gctx)
		return err
	})

	// Wait for all tests to complete
	// If any test fails, the error will be returned
	return eg.Wait()
}

// Build a ready-to-use development environment
func (m *MyModule) BuildEnv() *dagger.Container {
	nodeCache := dag.CacheVolume("node")
	return dag.Container().
		From("node:21-slim").
		WithDirectory("/src", m.Source).
		WithMountedCache("/root/.npm", nodeCache).
		WithWorkdir("/src").
		WithExec([]string{"npm", "install"})
}

Example​

Execute a Dagger Function which performs different types of tests by executing other Dagger Functions concurrently.

dagger -c 'my-module $(host | directory .) | run-all-tests'

Persist service state across runs​

The following Dagger Function uses a cache volume to persist a Redis service's data across Dagger Function runs.

package main

import (
	"context"

	"dagger/my-module/internal/dagger"
)

type MyModule struct{}

// Create Redis service and client
func (m *MyModule) Redis(ctx context.Context) *dagger.Container {
	redisSrv := dag.Container().
		From("redis").
		WithExposedPort(6379).
		WithMountedCache("/data", dag.CacheVolume("my-redis")).
		WithWorkdir("/data").
		AsService(dagger.ContainerAsServiceOpts{UseEntrypoint: true})

	redisCLI := dag.Container().
		From("redis").
		WithServiceBinding("redis-srv", redisSrv).
		WithEntrypoint([]string{"redis-cli", "-h", "redis-srv"})

	return redisCLI
}

var execOpts = dagger.ContainerWithExecOpts{
	UseEntrypoint: true,
}

// Set key and value in Redis service
func (m *MyModule) Set(
	ctx context.Context,
	// The cache key to set
	key string,
	// The cache value to set
	value string,
) (string, error) {
	return m.Redis(ctx).
		WithExec([]string{"set", key, value}, execOpts).
		WithExec([]string{"save"}, execOpts).
		Stdout(ctx)
}

// Get value from Redis service
func (m *MyModule) Get(
	ctx context.Context,
	// The cache key to get
	key string,
) (string, error) {
	return m.Redis(ctx).
		WithExec([]string{"get", key}, execOpts).
		Stdout(ctx)
}

Example​

  • Save data to a Redis service which uses a cache volume to persist a key named foo with value `123:

    dagger -c 'set foo 123'

  • Retrieve the value of the key foo after recreating the service state from the cache volume:

    dagger -c 'get foo'

Add OCI annotations to image​

The following Dagger Function adds OpenContainer Initiative (OCI) annotations to an image.

package main

import (
	"context"
	"fmt"
	"math"
	"math/rand/v2"
)

type MyModule struct{}

// Build and publish image with OCI annotations
func (m *MyModule) Build(ctx context.Context) (string, error) {
	address, err := dag.Container().
		From("alpine:latest").
		WithExec([]string{"apk", "add", "git"}).
		WithWorkdir("/src").
		WithExec([]string{"git", "clone", "https://github.com/dagger/dagger", "."}).
		WithAnnotation("org.opencontainers.image.authors", "John Doe").
		WithAnnotation("org.opencontainers.image.title", "Dagger source image viewer").
		Publish(ctx, fmt.Sprintf("ttl.sh/custom-image-%.0f", math.Floor(rand.Float64()*10000000))) //#nosec
	if err != nil {
		return "", err
	}
	return address, nil
}

Example​

Build and publish an image with OCI annotations:

dagger -c build

Add OCI labels to image​

The following Dagger Function adds OpenContainer Initiative (OCI) labels to an image.

package main

import (
	"context"
	"time"
)

type MyModule struct{}

// Build and publish image with OCI labels
func (m *MyModule) Build(
	ctx context.Context,
) (string, error) {
	ref, err := dag.Container().
		From("alpine").
		WithLabel("org.opencontainers.image.title", "my-alpine").
		WithLabel("org.opencontainers.image.version", "1.0").
		WithLabel("org.opencontainers.image.created", time.Now().String()).
		WithLabel("org.opencontainers.image.source", "https://github.com/alpinelinux/docker-alpine").
		WithLabel("org.opencontainers.image.licenses", "MIT").
		Publish(ctx, "ttl.sh/my-alpine")

	if err != nil {
		return "", err
	}

	return ref, nil
}

Example​

Build and publish an image with OCI labels:

dagger -c build

Invalidate cache​

The following function demonstrates how to invalidate the Dagger layer cache and force execution of subsequent workflow steps, by introducing a volatile time variable at a specific point in the Dagger workflow.

note
  • This is a temporary workaround until cache invalidation support is officially added to Dagger.
  • Changes in mounted cache volumes or secrets do not invalidate the Dagger layer cache.
package main

import (
	"context"
	"time"
)

type MyModule struct{}

// Run a build with cache invalidation
func (m *MyModule) Build(
	ctx context.Context,
) (string, error) {
	output, err := dag.Container().
		From("alpine").
		// comment out the line below to see the cached date output
		WithEnvVariable("CACHEBUSTER", time.Now().String()).
		WithExec([]string{"date"}).
		Stdout(ctx)

	if err != nil {
		return "", err
	}

	return output, nil
}

Example​

Print the date and time, invalidating the cache on each run. However, if the CACHEBUSTER environment variable is removed, the same value (the date and time on the first run) is printed on every run.

dagger -c build