kaniko/pkg/executor/build.go

/*
Copyright 2018 Google LLC

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package executor

import (
	"bytes"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"path/filepath"
	"strconv"

	"github.com/google/go-containerregistry/pkg/name"
	"github.com/google/go-containerregistry/pkg/v1"
	"github.com/google/go-containerregistry/pkg/v1/mutate"
	"github.com/google/go-containerregistry/pkg/v1/tarball"
	"github.com/moby/buildkit/frontend/dockerfile/instructions"
	"github.com/sirupsen/logrus"

	"github.com/GoogleContainerTools/kaniko/pkg/commands"
	"github.com/GoogleContainerTools/kaniko/pkg/constants"
	"github.com/GoogleContainerTools/kaniko/pkg/dockerfile"
	"github.com/GoogleContainerTools/kaniko/pkg/options"
	"github.com/GoogleContainerTools/kaniko/pkg/snapshot"
	"github.com/GoogleContainerTools/kaniko/pkg/util"
)

func DoBuild(opts *options.KanikoOptions) (v1.Image, error) {
	// Parse dockerfile and unpack base image to root
	stages, err := dockerfile.Stages(opts.DockerfilePath, opts.Target)
	if err != nil {
		return nil, err
	}

	hasher, err := getHasher(opts.SnapshotMode)
	if err != nil {
		return nil, err
	}
	for index, stage := range stages {
		finalStage := finalStage(index, opts.Target, stages)
		// Unpack file system to root
		sourceImage, err := util.RetrieveSourceImage(index, opts.BuildArgs, stages)
		if err != nil {
			return nil, err
		}
		if err := util.GetFSFromImage(constants.RootDir, sourceImage); err != nil {
			return nil, err
		}
		l := snapshot.NewLayeredMap(hasher)
		snapshotter := snapshot.NewSnapshotter(l, constants.RootDir)
		// Take initial snapshot
		if err := snapshotter.Init(); err != nil {
			return nil, err
		}
		imageConfig, err := util.RetrieveConfigFile(sourceImage)
		if err != nil {
			return nil, err
		}
		if err := resolveOnBuild(&stage, &imageConfig.Config); err != nil {
			return nil, err
		}
		buildArgs := dockerfile.NewBuildArgs(opts.BuildArgs)
		for index, cmd := range stage.Commands {
			finalCmd := index == len(stage.Commands)-1
			dockerCommand, err := commands.GetCommand(cmd, opts.SrcContext)
			if err != nil {
				return nil, err
			}
			if dockerCommand == nil {
				continue
			}
			if err := dockerCommand.ExecuteCommand(&imageConfig.Config, buildArgs); err != nil {
				return nil, err
			}
			snapshotFiles := dockerCommand.FilesToSnapshot()
			var contents []byte

			// If this is an intermediate stage, we only snapshot for the last command and we
			// want to snapshot the entire filesystem since we aren't tracking what was changed
			// by previous commands.
			if !finalStage {
				if finalCmd {
					contents, err = snapshotter.TakeSnapshotFS()
				}
			} else {
				// If we are in single snapshot mode, we only take a snapshot once, after all
				// commands have completed.
				if opts.SingleSnapshot {
					if finalCmd {
						contents, err = snapshotter.TakeSnapshotFS()
					}
				} else {
					// Otherwise, in the final stage we take a snapshot at each command. If we know
					// the files that were changed, we'll snapshot those explicitly, otherwise we'll
					// check if anything in the filesystem changed.
					if snapshotFiles != nil {
						contents, err = snapshotter.TakeSnapshot(snapshotFiles)
					} else {
						contents, err = snapshotter.TakeSnapshotFS()
					}
				}
			}
			if err != nil {
				return nil, fmt.Errorf("Error taking snapshot of files for command %s: %s", dockerCommand, err)
			}

			util.MoveVolumeWhitelistToWhitelist()
			if contents == nil {
				logrus.Info("No files were changed, appending empty layer to config. No layer added to image.")
				continue
			}
			// Append the layer to the image
			opener := func() (io.ReadCloser, error) {
				return ioutil.NopCloser(bytes.NewReader(contents)), nil
			}
			layer, err := tarball.LayerFromOpener(opener)
			if err != nil {
				return nil, err
			}
			sourceImage, err = mutate.Append(sourceImage,
				mutate.Addendum{
					Layer: layer,
					History: v1.History{
						Author:    constants.Author,
						CreatedBy: dockerCommand.CreatedBy(),
					},
				},
			)
			if err != nil {
				return nil, err
			}
		}
		sourceImage, err = mutate.Config(sourceImage, imageConfig.Config)
		if err != nil {
			return nil, err
		}
		if finalStage {
			if opts.Reproducible {
				sourceImage, err = mutate.Canonical(sourceImage)
				if err != nil {
					return nil, err
				}
			}
			return sourceImage, nil
		}
		if dockerfile.SaveStage(index, stages) {
			if err := saveStageAsTarball(index, sourceImage); err != nil {
				return nil, err
			}
			if err := extractImageToDependecyDir(index, sourceImage); err != nil {
				return nil, err
			}
		}
		// Delete the filesystem
		if err := util.DeleteFilesystem(); err != nil {
			return nil, err
		}
	}
	return nil, err
}

func finalStage(index int, target string, stages []instructions.Stage) bool {
	if index == len(stages)-1 {
		return true
	}
	if target == "" {
		return false
	}
	return target == stages[index].Name
}

func extractImageToDependecyDir(index int, image v1.Image) error {
	dependencyDir := filepath.Join(constants.KanikoDir, strconv.Itoa(index))
	if err := os.MkdirAll(dependencyDir, 0755); err != nil {
		return err
	}
	logrus.Infof("trying to extract to %s", dependencyDir)
	return util.GetFSFromImage(dependencyDir, image)
}

func saveStageAsTarball(stageIndex int, image v1.Image) error {
	destRef, err := name.NewTag("temp/tag", name.WeakValidation)
	if err != nil {
		return err
	}
	if err := os.MkdirAll(constants.KanikoIntermediateStagesDir, 0750); err != nil {
		return err
	}
	tarPath := filepath.Join(constants.KanikoIntermediateStagesDir, strconv.Itoa(stageIndex))
	logrus.Infof("Storing source image from stage %d at path %s", stageIndex, tarPath)
	return tarball.WriteToFile(tarPath, destRef, image, nil)
}

func getHasher(snapshotMode string) (func(string) (string, error), error) {
	if snapshotMode == constants.SnapshotModeTime {
		logrus.Info("Only file modification time will be considered when snapshotting")
		return util.MtimeHasher(), nil
	}
	if snapshotMode == constants.SnapshotModeFull {
		return util.Hasher(), nil
	}
	return nil, fmt.Errorf("%s is not a valid snapshot mode", snapshotMode)
}

func resolveOnBuild(stage *instructions.Stage, config *v1.Config) error {
	if config.OnBuild == nil {
		return nil
	}
	// Otherwise, parse into commands
	cmds, err := dockerfile.ParseCommands(config.OnBuild)
	if err != nil {
		return err
	}
	// Append to the beginning of the commands in the stage
	stage.Commands = append(cmds, stage.Commands...)
	logrus.Infof("Executing %v build triggers", len(cmds))

	// Blank out the Onbuild command list for this image
	config.OnBuild = nil
	return nil
}