Method Builder

src/cmd/linuxkit/pkglib/dockerimpl.go:222–251

Builder ensure that a builder container exists or return an error. Process: 1. Get an appropriate docker context. 2. Using the appropriate context, try to find a docker container named `linuxkit-builder` in that context. 3. Return a reference to that container. To get the appropriate docker conte

(ctx context.Context, dockerContext, builderImage, builderConfigPath, platform string, restart bool)

// 2. try to find an existing named runner with the pattern; if it succeeds, we are done; if not, try next.
// 3. try to create a generic builder using the default context named "linuxkit".
func (dr *dockerRunnerImpl) Builder(ctx context.Context, dockerContext, builderImage, builderConfigPath, platform string, restart bool) (*buildkitClient.Client, error) {
	// if we were given a context, we must find a builder and use it, or create one and use it
	if dockerContext != "" {
		// does the context exist?
		if err := dr.command(nil, io.Discard, io.Discard, "context", "inspect", dockerContext); err != nil {
			return nil, fmt.Errorf("provided docker context '%s' not found", dockerContext)
		}
		client, err := dr.builderEnsureContainer(ctx, buildkitBuilderName, builderImage, builderConfigPath, platform, dockerContext, restart)
		if err != nil {
			return nil, fmt.Errorf("error preparing builder based on context '%s': %v", dockerContext, err)
		}
		return client, nil
	}

	// no provided dockerContext, so look for one based on platform-specific name
	dockerContext = fmt.Sprintf("%s-%s", "linuxkit", strings.ReplaceAll(platform, "/", "-"))
	if err := dr.command(nil, io.Discard, io.Discard, "context", "inspect", dockerContext); err == nil {
		// we found an appropriately named context, so let us try to use it or error out
		if client, err := dr.builderEnsureContainer(ctx, buildkitBuilderName, builderImage, builderConfigPath, platform, dockerContext, restart); err == nil {
			return client, nil
		}
	}

	// create a generic builder
	client, err := dr.builderEnsureContainer(ctx, buildkitBuilderName, builderImage, builderConfigPath, "", "default", restart)
	if err != nil {
		return nil, fmt.Errorf("error ensuring builder container in default context: %v", err)
	}
	return client, nil
}

// builderEnsureContainer provided a name of a docker context, ensure that the builder container exists and
// is running the appropriate version of buildkit. If it does not exist, create it; if it is running