blob: b74c1ba6aef85623b5c71bd21726ff6b5e376bf3 [file] [log] [blame]
// builder is the evaluation step in the Dockerfile parse/evaluate pipeline.
// It incorporates a dispatch table based on the parser.Node values (see the
// parser package for more information) that are yielded from the parser itself.
// Calling NewBuilder with the BuildOpts struct can be used to customize the
// experience for execution purposes only. Parsing is controlled in the parser
// package, and this division of resposibility should be respected.
// Please see the jump table targets for the actual invocations, most of which
// will call out to the functions in internals.go to deal with their tasks.
// ONBUILD is a special case, which is covered in the onbuild() func in
// dispatchers.go.
// The evaluator uses the concept of "steps", which are usually each processable
// line in the Dockerfile. Each step is numbered and certain actions are taken
// before and after each step, such as creating an image ID and removing temporary
// containers and images. Note that ONBUILD creates a kinda-sorta "sub run" which
// includes its own set of steps (usually only one of them).
package builder
import (
log ""
var (
ErrDockerfileEmpty = errors.New("Dockerfile cannot be empty")
// Environment variable interpolation will happen on these statements only.
var replaceEnvAllowed = map[string]struct{}{
command.Env: {},
command.Label: {},
command.Add: {},
command.Copy: {},
command.Workdir: {},
command.Expose: {},
command.Volume: {},
command.User: {},
var evaluateTable map[string]func(*Builder, []string, map[string]bool, string) error
func init() {
evaluateTable = map[string]func(*Builder, []string, map[string]bool, string) error{
command.Env: env,
command.Label: label,
command.Maintainer: maintainer,
command.Add: add,
command.Copy: dispatchCopy, // copy() is a go builtin
command.From: from,
command.Onbuild: onbuild,
command.Workdir: workdir,
command.Run: run,
command.Cmd: cmd,
command.Entrypoint: entrypoint,
command.Expose: expose,
command.Volume: volume,
command.User: user,
command.Insert: insert,
// internal struct, used to maintain configuration of the Dockerfile's
// processing as it evaluates the parsing result.
type Builder struct {
Daemon *daemon.Daemon
Engine *engine.Engine
// effectively stdio for the run. Because it is not stdio, I said
// "Effectively". Do not use stdio anywhere in this package for any reason.
OutStream io.Writer
ErrStream io.Writer
Verbose bool
UtilizeCache bool
cacheBusted bool
// controls how images and containers are handled between steps.
Remove bool
ForceRemove bool
Pull bool
// set this to true if we want the builder to not commit between steps.
// This is useful when we only want to use the evaluator table to generate
// the final configs of the Dockerfile but dont want the layers
disableCommit bool
AuthConfig *registry.AuthConfig
AuthConfigFile *registry.ConfigFile
// Deprecated, original writer used for ImagePull. To be removed.
OutOld io.Writer
StreamFormatter *utils.StreamFormatter
Config *runconfig.Config // runconfig for cmd, run, entrypoint etc.
// both of these are controlled by the Remove and ForceRemove options in BuildOpts
TmpContainers map[string]struct{} // a map of containers used for removes
dockerfileName string // name of Dockerfile
dockerfile *parser.Node // the syntax tree of the dockerfile
image string // image name for commit processing
maintainer string // maintainer name. could probably be removed.
cmdSet bool // indicates is CMD was set in current Dockerfile
context tarsum.TarSum // the context is a tarball that is uploaded by the client
contextPath string // the path of the temporary directory the local context is unpacked to (server side)
noBaseImage bool // indicates that this build does not start from any base image, but is being built from an empty file system.
// Set resource restrictions for build containers
cpuSetCpus string
cpuShares int64
memory int64
memorySwap int64
cancelled <-chan struct{} // When closed, job was cancelled.
// Run the builder with the context. This is the lynchpin of this package. This
// will (barring errors):
// * call readContext() which will set up the temporary directory and unpack
// the context into it.
// * read the dockerfile
// * parse the dockerfile
// * walk the parse tree and execute it by dispatching to handlers. If Remove
// or ForceRemove is set, additional cleanup around containers happens after
// processing.
// * Print a happy message and return the image ID.
func (b *Builder) Run(context io.Reader) (string, error) {
if err := b.readContext(context); err != nil {
return "", err
defer func() {
if err := os.RemoveAll(b.contextPath); err != nil {
log.Debugf("[BUILDER] failed to remove temporary context: %s", err)
if err := b.readDockerfile(); err != nil {
return "", err
// some initializations that would not have been supplied by the caller.
b.Config = &runconfig.Config{}
b.TmpContainers = map[string]struct{}{}
for i, n := range b.dockerfile.Children {
select {
case <-b.cancelled:
log.Debug("Builder: build cancelled!")
fmt.Fprintf(b.OutStream, "Build cancelled")
return "", fmt.Errorf("Build cancelled")
// Not cancelled yet, keep going...
if err := b.dispatch(i, n); err != nil {
if b.ForceRemove {
return "", err
fmt.Fprintf(b.OutStream, " ---> %s\n", common.TruncateID(b.image))
if b.Remove {
if b.image == "" {
return "", fmt.Errorf("No image was generated. Is your Dockerfile empty?")
fmt.Fprintf(b.OutStream, "Successfully built %s\n", common.TruncateID(b.image))
return b.image, nil
// Reads a Dockerfile from the current context. It assumes that the
// 'filename' is a relative path from the root of the context
func (b *Builder) readDockerfile() error {
// If no -f was specified then look for 'Dockerfile'. If we can't find
// that then look for 'dockerfile'. If neither are found then default
// back to 'Dockerfile' and use that in the error message.
if b.dockerfileName == "" {
b.dockerfileName = api.DefaultDockerfileName
tmpFN := filepath.Join(b.contextPath, api.DefaultDockerfileName)
if _, err := os.Lstat(tmpFN); err != nil {
tmpFN = filepath.Join(b.contextPath, strings.ToLower(api.DefaultDockerfileName))
if _, err := os.Lstat(tmpFN); err == nil {
b.dockerfileName = strings.ToLower(api.DefaultDockerfileName)
origFile := b.dockerfileName
filename, err := symlink.FollowSymlinkInScope(filepath.Join(b.contextPath, origFile), b.contextPath)
if err != nil {
return fmt.Errorf("The Dockerfile (%s) must be within the build context", origFile)
fi, err := os.Lstat(filename)
if os.IsNotExist(err) {
return fmt.Errorf("Cannot locate specified Dockerfile: %s", origFile)
if fi.Size() == 0 {
return ErrDockerfileEmpty
f, err := os.Open(filename)
if err != nil {
return err
b.dockerfile, err = parser.Parse(f)
if err != nil {
return err
// After the Dockerfile has been parsed, we need to check the .dockerignore
// file for either "Dockerfile" or ".dockerignore", and if either are
// present then erase them from the build context. These files should never
// have been sent from the client but we did send them to make sure that
// we had the Dockerfile to actually parse, and then we also need the
// .dockerignore file to know whether either file should be removed.
// Note that this assumes the Dockerfile has been read into memory and
// is now safe to be removed.
excludes, _ := utils.ReadDockerIgnore(filepath.Join(b.contextPath, ".dockerignore"))
if rm, _ := fileutils.Matches(".dockerignore", excludes); rm == true {
os.Remove(filepath.Join(b.contextPath, ".dockerignore"))
if rm, _ := fileutils.Matches(b.dockerfileName, excludes); rm == true {
os.Remove(filepath.Join(b.contextPath, b.dockerfileName))
return nil
// This method is the entrypoint to all statement handling routines.
// Almost all nodes will have this structure:
// Child[Node, Node, Node] where Child is from parser.Node.Children and each
// node comes from parser.Node.Next. This forms a "line" with a statement and
// arguments and we process them in this normalized form by hitting
// evaluateTable with the leaf nodes of the command and the Builder object.
// ONBUILD is a special case; in this case the parser will emit:
// Child[Node, Child[Node, Node...]] where the first node is the literal
// "onbuild" and the child entrypoint is the command of the ONBUILD statmeent,
// such as `RUN` in ONBUILD RUN foo. There is special case logic in here to
// deal with that, at least until it becomes more of a general concern with new
// features.
func (b *Builder) dispatch(stepN int, ast *parser.Node) error {
cmd := ast.Value
attrs := ast.Attributes
original := ast.Original
strs := []string{}
msg := fmt.Sprintf("Step %d : %s", stepN, strings.ToUpper(cmd))
if cmd == "onbuild" {
if ast.Next == nil {
return fmt.Errorf("ONBUILD requires at least one argument")
ast = ast.Next.Children[0]
strs = append(strs, ast.Value)
msg += " " + ast.Value
// count the number of nodes that we are going to traverse first
// so we can pre-create the argument and message array. This speeds up the
// allocation of those list a lot when they have a lot of arguments
cursor := ast
var n int
for cursor.Next != nil {
cursor = cursor.Next
l := len(strs)
strList := make([]string, n+l)
copy(strList, strs)
msgList := make([]string, n)
var i int
for ast.Next != nil {
ast = ast.Next
var str string
str = ast.Value
if _, ok := replaceEnvAllowed[cmd]; ok {
var err error
str, err = ProcessWord(ast.Value, b.Config.Env)
if err != nil {
return err
strList[i+l] = str
msgList[i] = ast.Value
msg += " " + strings.Join(msgList, " ")
fmt.Fprintln(b.OutStream, msg)
// XXX yes, we skip any cmds that are not valid; the parser should have
// picked these out already.
if f, ok := evaluateTable[cmd]; ok {
return f(b, strList, attrs, original)
return fmt.Errorf("Unknown instruction: %s", strings.ToUpper(cmd))