builder/dockerfile/internals.go

package dockerfile

// internals for handling commands. Covers many areas and a lot of
// non-contiguous functionality. Please read the comments.

import (
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"strings"

	"github.com/Sirupsen/logrus"
	"github.com/docker/docker/api/types"
	"github.com/docker/docker/api/types/backend"
	"github.com/docker/docker/api/types/container"
	containerpkg "github.com/docker/docker/container"
	"github.com/docker/docker/pkg/jsonmessage"
	"github.com/docker/docker/pkg/stringid"
	"github.com/pkg/errors"
)

func (b *Builder) commit(dispatchState *dispatchState, comment string) error {
	if b.disableCommit {
		return nil
	}
	if !dispatchState.hasFromImage() {
		return errors.New("Please provide a source image with `from` prior to commit")
	}

	runConfigWithCommentCmd := copyRunConfig(dispatchState.runConfig, withCmdComment(comment))
	hit, err := b.probeCache(dispatchState, runConfigWithCommentCmd)
	if err != nil || hit {
		return err
	}
	id, err := b.create(runConfigWithCommentCmd)
	if err != nil {
		return err
	}

	return b.commitContainer(dispatchState, id, runConfigWithCommentCmd)
}

// TODO: see if any args can be dropped
func (b *Builder) commitContainer(dispatchState *dispatchState, id string, containerConfig *container.Config) error {
	if b.disableCommit {
		return nil
	}

	commitCfg := &backend.ContainerCommitConfig{
		ContainerCommitConfig: types.ContainerCommitConfig{
			Author: dispatchState.maintainer,
			Pause:  true,
			// TODO: this should be done by Commit()
			Config: copyRunConfig(dispatchState.runConfig),
		},
		ContainerConfig: containerConfig,
	}

	// Commit the container
	imageID, err := b.docker.Commit(id, commitCfg)
	if err != nil {
		return err
	}

	dispatchState.imageID = imageID
	b.buildStages.update(imageID, dispatchState.runConfig)
	return nil
}

func (b *Builder) performCopy(state *dispatchState, inst copyInstruction) error {
	srcHash := getSourceHashFromInfos(inst.infos)

	// TODO: should this have been using origPaths instead of srcHash in the comment?
	runConfigWithCommentCmd := copyRunConfig(
		state.runConfig,
		withCmdCommentString(fmt.Sprintf("%s %s in %s ", inst.cmdName, srcHash, inst.dest)))
	if hit, err := b.probeCache(state, runConfigWithCommentCmd); err != nil || hit {
		return err
	}

	container, err := b.docker.ContainerCreate(types.ContainerCreateConfig{
		Config: runConfigWithCommentCmd,
		// Set a log config to override any default value set on the daemon
		HostConfig: &container.HostConfig{LogConfig: defaultLogConfig},
	})
	if err != nil {
		return err
	}
	b.tmpContainers[container.ID] = struct{}{}

	// Twiddle the destination when it's a relative path - meaning, make it
	// relative to the WORKINGDIR
	dest, err := normaliseDest(inst.cmdName, state.runConfig.WorkingDir, inst.dest)
	if err != nil {
		return err
	}

	for _, info := range inst.infos {
		if err := b.docker.CopyOnBuild(container.ID, dest, info.root, info.path, inst.allowLocalDecompression); err != nil {
			return err
		}
	}
	return b.commitContainer(state, container.ID, runConfigWithCommentCmd)
}

// For backwards compat, if there's just one info then use it as the
// cache look-up string, otherwise hash 'em all into one
func getSourceHashFromInfos(infos []copyInfo) string {
	if len(infos) == 1 {
		return infos[0].hash
	}
	var hashs []string
	for _, info := range infos {
		hashs = append(hashs, info.hash)
	}
	return hashStringSlice("multi", hashs)
}

func hashStringSlice(prefix string, slice []string) string {
	hasher := sha256.New()
	hasher.Write([]byte(strings.Join(slice, ",")))
	return prefix + ":" + hex.EncodeToString(hasher.Sum(nil))
}

type runConfigModifier func(*container.Config)

func copyRunConfig(runConfig *container.Config, modifiers ...runConfigModifier) *container.Config {
	copy := *runConfig
	for _, modifier := range modifiers {
		modifier(&copy)
	}
	return &copy
}

func withCmd(cmd []string) runConfigModifier {
	return func(runConfig *container.Config) {
		runConfig.Cmd = cmd
	}
}

// withCmdComment sets Cmd to a nop comment string. See withCmdCommentString for
// why there are two almost identical versions of this.
func withCmdComment(comment string) runConfigModifier {
	return func(runConfig *container.Config) {
		runConfig.Cmd = append(getShell(runConfig), "#(nop) ", comment)
	}
}

// withCmdCommentString exists to maintain compatibility with older versions.
// A few instructions (workdir, copy, add) used a nop comment that is a single arg
// where as all the other instructions used a two arg comment string. This
// function implements the single arg version.
func withCmdCommentString(comment string) runConfigModifier {
	return func(runConfig *container.Config) {
		runConfig.Cmd = append(getShell(runConfig), "#(nop) "+comment)
	}
}

func withEnv(env []string) runConfigModifier {
	return func(runConfig *container.Config) {
		runConfig.Env = env
	}
}

// withEntrypointOverride sets an entrypoint on runConfig if the command is
// not empty. The entrypoint is left unmodified if command is empty.
//
// The dockerfile RUN instruction expect to run without an entrypoint
// so the runConfig entrypoint needs to be modified accordingly. ContainerCreate
// will change a []string{""} entrypoint to nil, so we probe the cache with the
// nil entrypoint.
func withEntrypointOverride(cmd []string, entrypoint []string) runConfigModifier {
	return func(runConfig *container.Config) {
		if len(cmd) > 0 {
			runConfig.Entrypoint = entrypoint
		}
	}
}

// getShell is a helper function which gets the right shell for prefixing the
// shell-form of RUN, ENTRYPOINT and CMD instructions
func getShell(c *container.Config) []string {
	if 0 == len(c.Shell) {
		return append([]string{}, defaultShell[:]...)
	}
	return append([]string{}, c.Shell[:]...)
}

// probeCache checks if cache match can be found for current build instruction.
// If an image is found, probeCache returns `(true, nil)`.
// If no image is found, it returns `(false, nil)`.
// If there is any error, it returns `(false, err)`.
func (b *Builder) probeCache(dispatchState *dispatchState, runConfig *container.Config) (bool, error) {
	c := b.imageCache
	if c == nil || b.options.NoCache || b.cacheBusted {
		return false, nil
	}
	cache, err := c.GetCache(dispatchState.imageID, runConfig)
	if err != nil {
		return false, err
	}
	if len(cache) == 0 {
		logrus.Debugf("[BUILDER] Cache miss: %s", runConfig.Cmd)
		b.cacheBusted = true
		return false, nil
	}

	fmt.Fprint(b.Stdout, " ---> Using cache\n")
	logrus.Debugf("[BUILDER] Use cached version: %s", runConfig.Cmd)
	dispatchState.imageID = string(cache)
	b.buildStages.update(dispatchState.imageID, runConfig)

	return true, nil
}

func (b *Builder) create(runConfig *container.Config) (string, error) {
	resources := container.Resources{
		CgroupParent: b.options.CgroupParent,
		CPUShares:    b.options.CPUShares,
		CPUPeriod:    b.options.CPUPeriod,
		CPUQuota:     b.options.CPUQuota,
		CpusetCpus:   b.options.CPUSetCPUs,
		CpusetMems:   b.options.CPUSetMems,
		Memory:       b.options.Memory,
		MemorySwap:   b.options.MemorySwap,
		Ulimits:      b.options.Ulimits,
	}

	// TODO: why not embed a hostconfig in builder?
	hostConfig := &container.HostConfig{
		SecurityOpt: b.options.SecurityOpt,
		Isolation:   b.options.Isolation,
		ShmSize:     b.options.ShmSize,
		Resources:   resources,
		NetworkMode: container.NetworkMode(b.options.NetworkMode),
		// Set a log config to override any default value set on the daemon
		LogConfig:  defaultLogConfig,
		ExtraHosts: b.options.ExtraHosts,
	}

	// Create the container
	c, err := b.docker.ContainerCreate(types.ContainerCreateConfig{
		Config:     runConfig,
		HostConfig: hostConfig,
	})
	if err != nil {
		return "", err
	}
	for _, warning := range c.Warnings {
		fmt.Fprintf(b.Stdout, " ---> [Warning] %s\n", warning)
	}

	b.tmpContainers[c.ID] = struct{}{}
	fmt.Fprintf(b.Stdout, " ---> Running in %s\n", stringid.TruncateID(c.ID))
	return c.ID, nil
}

var errCancelled = errors.New("build cancelled")

func (b *Builder) run(cID string, cmd []string) (err error) {
	attached := make(chan struct{})
	errCh := make(chan error)
	go func() {
		errCh <- b.docker.ContainerAttachRaw(cID, nil, b.Stdout, b.Stderr, true, attached)
	}()

	select {
	case err := <-errCh:
		return err
	case <-attached:
	}

	finished := make(chan struct{})
	cancelErrCh := make(chan error, 1)
	go func() {
		select {
		case <-b.clientCtx.Done():
			logrus.Debugln("Build cancelled, killing and removing container:", cID)
			b.docker.ContainerKill(cID, 0)
			b.removeContainer(cID)
			cancelErrCh <- errCancelled
		case <-finished:
			cancelErrCh <- nil
		}
	}()

	if err := b.docker.ContainerStart(cID, nil, "", ""); err != nil {
		close(finished)
		if cancelErr := <-cancelErrCh; cancelErr != nil {
			logrus.Debugf("Build cancelled (%v) and got an error from ContainerStart: %v",
				cancelErr, err)
		}
		return err
	}

	// Block on reading output from container, stop on err or chan closed
	if err := <-errCh; err != nil {
		close(finished)
		if cancelErr := <-cancelErrCh; cancelErr != nil {
			logrus.Debugf("Build cancelled (%v) and got an error from errCh: %v",
				cancelErr, err)
		}
		return err
	}

	waitC, err := b.docker.ContainerWait(b.clientCtx, cID, containerpkg.WaitConditionNotRunning)
	if err != nil {
		// Unable to begin waiting for container.
		close(finished)
		if cancelErr := <-cancelErrCh; cancelErr != nil {
			logrus.Debugf("Build cancelled (%v) and unable to begin ContainerWait: %d", cancelErr, err)
		}
		return err
	}

	if status := <-waitC; status.ExitCode() != 0 {
		close(finished)
		if cancelErr := <-cancelErrCh; cancelErr != nil {
			logrus.Debugf("Build cancelled (%v) and got a non-zero code from ContainerWait: %d", cancelErr, status.ExitCode())
		}
		// TODO: change error type, because jsonmessage.JSONError assumes HTTP
		return &jsonmessage.JSONError{
			Message: fmt.Sprintf("The command '%s' returned a non-zero code: %d", strings.Join(cmd, " "), status.ExitCode()),
			Code:    status.ExitCode(),
		}
	}
	close(finished)
	return <-cancelErrCh
}

func (b *Builder) removeContainer(c string) error {
	rmConfig := &types.ContainerRmConfig{
		ForceRemove:  true,
		RemoveVolume: true,
	}
	if err := b.docker.ContainerRm(c, rmConfig); err != nil {
		fmt.Fprintf(b.Stdout, "Error removing intermediate container %s: %v\n", stringid.TruncateID(c), err)
		return err
	}
	return nil
}

func (b *Builder) clearTmp() {
	for c := range b.tmpContainers {
		if err := b.removeContainer(c); err != nil {
			return
		}
		delete(b.tmpContainers, c)
		fmt.Fprintf(b.Stdout, "Removing intermediate container %s\n", stringid.TruncateID(c))
	}
}