dap: add stack traces with next and continue functionality

It is now possible to send next and continue as separate signals. When
executing a build, the debug adapter will divide the LLB graph into
regions. Each region corresponds to an uninterrupted chain of
instructions. It will also record which regions depend on which other
ones.

This determines the execution order and it also determines what the
stack traces look like.

When continue is used, we will attempt to evaluate the last leaf node
(the head). If we push next, we will determine which digest would be the
next one to be processed.

In the future, this will be used to also support breakpoints.

Signed-off-by: Jonathan A. Sternberg <jonathan.sternberg@docker.com>
This commit is contained in:
Jonathan A. Sternberg
2025-07-03 09:18:55 -05:00
parent 758ea75f60
commit 4f2e23a9b8
6 changed files with 644 additions and 103 deletions
+2 -2
View File
@@ -314,7 +314,7 @@ func toRepoOnly(in string) (string, error) {
}
type (
EvaluateFunc func(ctx context.Context, name string, c gateway.Client, res *gateway.Result) error
EvaluateFunc func(ctx context.Context, name string, c gateway.Client, res *gateway.Result, opt Options) error
Handler struct {
Evaluate EvaluateFunc
}
@@ -525,7 +525,7 @@ func BuildWithResultHandler(ctx context.Context, nodes []builder.Node, opts map[
// invoke custom evaluate handler if it is present
if bh != nil && bh.Evaluate != nil {
if err := bh.Evaluate(ctx, k, c, res); err != nil {
if err := bh.Evaluate(ctx, k, c, res, opt); err != nil {
return nil, err
}
} else if forceEval {
+103 -88
View File
@@ -1,11 +1,14 @@
package dap
import (
"bytes"
"context"
"encoding/json"
"fmt"
"io"
"path"
"sync"
"sync/atomic"
"github.com/docker/buildx/build"
"github.com/google/go-dap"
@@ -28,6 +31,9 @@ type Adapter[T any] struct {
threads map[int]*thread
threadsMu sync.RWMutex
nextThreadID int
sourceMap sourceMap
idPool *idPool
}
func New[T any](cfg *build.InvokeConfig) *Adapter[T] {
@@ -38,6 +44,7 @@ func New[T any](cfg *build.InvokeConfig) *Adapter[T] {
evaluateReqCh: make(chan *evaluateRequest),
threads: make(map[int]*thread),
nextThreadID: 1,
idPool: new(idPool),
}
if cfg != nil {
d.cfg = *cfg
@@ -131,7 +138,16 @@ func (d *Adapter[T]) Continue(c Context, req *dap.ContinueRequest, resp *dap.Con
t := d.threads[req.Arguments.ThreadId]
d.threadsMu.RUnlock()
t.Resume(c)
t.Continue()
return nil
}
func (d *Adapter[T]) Next(c Context, req *dap.NextRequest, resp *dap.NextResponse) error {
d.threadsMu.RLock()
t := d.threads[req.Arguments.ThreadId]
d.threadsMu.RUnlock()
t.Next()
return nil
}
@@ -182,7 +198,7 @@ func (d *Adapter[T]) launch(c Context) {
started := c.Go(func(c Context) {
defer d.deleteThread(c, t)
defer close(req.errCh)
req.errCh <- t.Evaluate(c, req.c, req.ref, req.meta, d.cfg)
req.errCh <- t.Evaluate(c, req.c, req.ref, req.meta, req.inputs)
})
if !started {
@@ -199,6 +215,8 @@ func (d *Adapter[T]) newThread(ctx Context, name string) (t *thread) {
t = &thread{
id: id,
name: name,
sourceMap: &d.sourceMap,
idPool: d.idPool,
}
d.threads[t.id] = t
d.nextThreadID++
@@ -240,27 +258,28 @@ type evaluateRequest struct {
c gateway.Client
ref gateway.Reference
meta map[string][]byte
inputs build.Inputs
errCh chan<- error
}
func (d *Adapter[T]) EvaluateResult(ctx context.Context, name string, c gateway.Client, res *gateway.Result) error {
func (d *Adapter[T]) EvaluateResult(ctx context.Context, name string, c gateway.Client, res *gateway.Result, inputs build.Inputs) error {
eg, _ := errgroup.WithContext(ctx)
if res.Ref != nil {
eg.Go(func() error {
return d.evaluateRef(ctx, name, c, res.Ref, res.Metadata)
return d.evaluateRef(ctx, name, c, res.Ref, res.Metadata, inputs)
})
}
for k, ref := range res.Refs {
refName := fmt.Sprintf("%s (%s)", name, k)
eg.Go(func() error {
return d.evaluateRef(ctx, refName, c, ref, res.Metadata)
return d.evaluateRef(ctx, refName, c, ref, res.Metadata, inputs)
})
}
return eg.Wait()
}
func (d *Adapter[T]) evaluateRef(ctx context.Context, name string, c gateway.Client, ref gateway.Reference, meta map[string][]byte) error {
func (d *Adapter[T]) evaluateRef(ctx context.Context, name string, c gateway.Client, ref gateway.Reference, meta map[string][]byte, inputs build.Inputs) error {
errCh := make(chan error, 1)
// Send a solve request to the launch routine
@@ -270,6 +289,7 @@ func (d *Adapter[T]) evaluateRef(ctx context.Context, name string, c gateway.Cli
c: c,
ref: ref,
meta: meta,
inputs: inputs,
errCh: errCh,
}
select {
@@ -307,16 +327,28 @@ func (d *Adapter[T]) StackTrace(c Context, req *dap.StackTraceRequest, resp *dap
return errors.Errorf("no such thread: %d", req.Arguments.ThreadId)
}
resp.Body.StackFrames = t.StackFrames()
resp.Body.StackFrames = t.StackTrace()
return nil
}
func (d *Adapter[T]) evaluate(ctx context.Context, name string, c gateway.Client, res *gateway.Result) error {
func (d *Adapter[T]) Source(c Context, req *dap.SourceRequest, resp *dap.SourceResponse) error {
fname := req.Arguments.Source.Path
dt, ok := d.sourceMap.Get(fname)
if !ok {
return errors.Errorf("file not found: %s", fname)
}
resp.Body.Content = string(dt)
return nil
}
func (d *Adapter[T]) evaluate(ctx context.Context, name string, c gateway.Client, res *gateway.Result, opt build.Options) error {
errCh := make(chan error, 1)
started := d.srv.Go(func(ctx Context) {
defer close(errCh)
errCh <- d.EvaluateResult(ctx, name, c, res)
errCh <- d.EvaluateResult(ctx, name, c, res, opt.Inputs)
})
if !started {
return context.Canceled
@@ -341,93 +373,16 @@ func (d *Adapter[T]) dapHandler() Handler {
Initialize: d.Initialize,
Launch: d.Launch,
Continue: d.Continue,
Next: d.Next,
SetBreakpoints: d.SetBreakpoints,
ConfigurationDone: d.ConfigurationDone,
Disconnect: d.Disconnect,
Threads: d.Threads,
StackTrace: d.StackTrace,
Source: d.Source,
}
}
type thread struct {
id int
name string
paused chan struct{}
rCtx *build.ResultHandle
mu sync.Mutex
}
func (t *thread) Evaluate(ctx Context, c gateway.Client, ref gateway.Reference, meta map[string][]byte, cfg build.InvokeConfig) error {
err := ref.Evaluate(ctx)
if reason, desc := t.needsDebug(cfg, err); reason != "" {
rCtx := build.NewResultHandle(ctx, c, ref, meta, err)
select {
case <-t.pause(ctx, rCtx, reason, desc):
case <-ctx.Done():
t.Resume(ctx)
return context.Cause(ctx)
}
}
return err
}
func (t *thread) needsDebug(cfg build.InvokeConfig, err error) (reason, desc string) {
if !cfg.NeedsDebug(err) {
return
}
if err != nil {
reason = "exception"
desc = "Encountered an error during result evaluation"
} else {
reason = "pause"
desc = "Result evaluation completed"
}
return
}
func (t *thread) pause(c Context, rCtx *build.ResultHandle, reason, desc string) <-chan struct{} {
if t.paused == nil {
t.paused = make(chan struct{})
}
t.rCtx = rCtx
c.C() <- &dap.StoppedEvent{
Event: dap.Event{Event: "stopped"},
Body: dap.StoppedEventBody{
Reason: reason,
Description: desc,
ThreadId: t.id,
},
}
return t.paused
}
func (t *thread) Resume(c Context) {
t.mu.Lock()
defer t.mu.Unlock()
if t.paused == nil {
return
}
if t.rCtx != nil {
t.rCtx.Done()
t.rCtx = nil
}
close(t.paused)
t.paused = nil
}
// TODO: return a suitable stack frame for the thread.
// For now, just returns nothing.
func (t *thread) StackFrames() []dap.StackFrame {
return []dap.StackFrame{}
}
func (d *Adapter[T]) Out() io.Writer {
return &adapterWriter[T]{d}
}
@@ -454,3 +409,63 @@ func (d *adapterWriter[T]) Write(p []byte) (n int, err error) {
}
return n, nil
}
type idPool struct {
next atomic.Int64
}
func (p *idPool) Get() int64 {
return p.next.Add(1)
}
func (p *idPool) Put(x int64) {
// noop
}
type sourceMap struct {
m sync.Map
}
func (s *sourceMap) Put(c Context, fname string, dt []byte) {
for {
old, loaded := s.m.LoadOrStore(fname, dt)
if !loaded {
c.C() <- &dap.LoadedSourceEvent{
Event: dap.Event{Event: "loadedSource"},
Body: dap.LoadedSourceEventBody{
Reason: "new",
Source: dap.Source{
Name: path.Base(fname),
Path: fname,
},
},
}
}
if bytes.Equal(old.([]byte), dt) {
// Nothing to do.
return
}
if s.m.CompareAndSwap(fname, old, dt) {
c.C() <- &dap.LoadedSourceEvent{
Event: dap.Event{Event: "loadedSource"},
Body: dap.LoadedSourceEventBody{
Reason: "changed",
Source: dap.Source{
Name: path.Base(fname),
Path: fname,
},
},
}
}
}
}
func (s *sourceMap) Get(fname string) ([]byte, bool) {
v, ok := s.m.Load(fname)
if !ok {
return nil, false
}
return v.([]byte), true
}
+2
View File
@@ -51,8 +51,10 @@ type Handler struct {
Disconnect HandlerFunc[*dap.DisconnectRequest, *dap.DisconnectResponse]
Terminate HandlerFunc[*dap.TerminateRequest, *dap.TerminateResponse]
Continue HandlerFunc[*dap.ContinueRequest, *dap.ContinueResponse]
Next HandlerFunc[*dap.NextRequest, *dap.NextResponse]
Restart HandlerFunc[*dap.RestartRequest, *dap.RestartResponse]
Threads HandlerFunc[*dap.ThreadsRequest, *dap.ThreadsResponse]
StackTrace HandlerFunc[*dap.StackTraceRequest, *dap.StackTraceResponse]
Evaluate HandlerFunc[*dap.EvaluateRequest, *dap.EvaluateResponse]
Source HandlerFunc[*dap.SourceRequest, *dap.SourceResponse]
}
+4
View File
@@ -117,6 +117,8 @@ func (s *Server) handleMessage(c Context, m dap.Message) (dap.ResponseMessage, e
return s.h.Terminate.Do(c, req)
case *dap.ContinueRequest:
return s.h.Continue.Do(c, req)
case *dap.NextRequest:
return s.h.Next.Do(c, req)
case *dap.RestartRequest:
return s.h.Restart.Do(c, req)
case *dap.ThreadsRequest:
@@ -125,6 +127,8 @@ func (s *Server) handleMessage(c Context, m dap.Message) (dap.ResponseMessage, e
return s.h.StackTrace.Do(c, req)
case *dap.EvaluateRequest:
return s.h.Evaluate.Do(c, req)
case *dap.SourceRequest:
return s.h.Source.Do(c, req)
default:
return nil, errors.New("not implemented")
}
+520
View File
@@ -0,0 +1,520 @@
package dap
import (
"context"
"path/filepath"
"slices"
"sync"
"github.com/docker/buildx/build"
"github.com/google/go-dap"
"github.com/moby/buildkit/client/llb"
gateway "github.com/moby/buildkit/frontend/gateway/client"
"github.com/moby/buildkit/solver/errdefs"
"github.com/moby/buildkit/solver/pb"
"github.com/opencontainers/go-digest"
"github.com/pkg/errors"
)
type thread struct {
// Persistent data.
id int
name string
// Persistent state from the adapter.
idPool *idPool
sourceMap *sourceMap
// Inputs to the evaluate call.
c gateway.Client
ref gateway.Reference
meta map[string][]byte
sourcePath string
// LLB state for the evaluate call.
def *llb.Definition
ops map[digest.Digest]*pb.Op
head digest.Digest
// Runtime state for the evaluate call.
regions []*region
regionsByDigest map[digest.Digest]int
// Controls pause.
paused chan stepType
mu sync.Mutex
// Attributes set when a thread is paused.
rCtx *build.ResultHandle
curPos digest.Digest
// Lazy attributes that are set when a thread is paused.
stackTrace []dap.StackFrame
}
type region struct {
// dependsOn means this thread depends on the result of another thread.
dependsOn map[int]struct{}
// digests is a set of digests associated with this thread.
digests []digest.Digest
}
type stepType int
const (
stepContinue stepType = iota
stepNext
)
func (t *thread) Evaluate(ctx Context, c gateway.Client, ref gateway.Reference, meta map[string][]byte, inputs build.Inputs) error {
if err := t.init(ctx, c, ref, meta, inputs); err != nil {
return err
}
defer t.reset()
step := stepNext
for {
pos, err := t.seekNext(ctx, step)
reason, desc := t.needsDebug(pos, step, err)
if reason == "" {
return err
}
select {
case step = <-t.pause(ctx, err, reason, desc):
case <-ctx.Done():
return context.Cause(ctx)
}
}
}
func (t *thread) init(ctx Context, c gateway.Client, ref gateway.Reference, meta map[string][]byte, inputs build.Inputs) error {
t.c = c
t.ref = ref
t.meta = meta
t.sourcePath = inputs.ContextPath
return t.createRegions(ctx)
}
func (t *thread) reset() {
t.c = nil
t.ref = nil
t.meta = nil
t.sourcePath = ""
t.ops = nil
}
func (t *thread) needsDebug(target digest.Digest, step stepType, err error) (reason, desc string) {
if err != nil {
reason = "exception"
desc = "Encountered an error during result evaluation"
} else if target != "" && step == stepNext {
reason = "step"
}
return
}
func (t *thread) pause(c Context, err error, reason, desc string) <-chan stepType {
t.mu.Lock()
defer t.mu.Unlock()
if t.paused != nil {
return t.paused
}
t.paused = make(chan stepType, 1)
t.rCtx = build.NewResultHandle(c, t.c, t.ref, t.meta, err)
if err != nil {
var solveErr *errdefs.SolveError
if errors.As(err, &solveErr) {
if dt, err := solveErr.Op.MarshalVT(); err == nil {
t.curPos = digest.FromBytes(dt)
}
}
}
c.C() <- &dap.StoppedEvent{
Event: dap.Event{Event: "stopped"},
Body: dap.StoppedEventBody{
Reason: reason,
Description: desc,
ThreadId: t.id,
},
}
return t.paused
}
func (t *thread) Continue() {
t.resume(stepContinue)
}
func (t *thread) Next() {
t.resume(stepNext)
}
func (t *thread) resume(step stepType) {
t.mu.Lock()
defer t.mu.Unlock()
if t.paused == nil {
return
}
if t.rCtx != nil {
t.rCtx.Done()
t.rCtx = nil
}
if t.stackTrace != nil {
for _, frame := range t.stackTrace {
t.idPool.Put(int64(frame.Id))
}
t.stackTrace = nil
}
t.paused <- step
close(t.paused)
t.paused = nil
}
func (t *thread) StackTrace() []dap.StackFrame {
t.mu.Lock()
defer t.mu.Unlock()
if t.paused == nil {
// Cannot compute stack trace when not paused.
// This should never happen, but protect ourself in
// case it does.
return []dap.StackFrame{}
}
if t.stackTrace == nil {
t.stackTrace = t.makeStackTrace()
}
return t.stackTrace
}
func (t *thread) getLLBState(ctx Context) error {
st, err := t.ref.ToState()
if err != nil {
return err
}
t.def, err = st.Marshal(ctx)
if err != nil {
return err
}
for _, src := range t.def.Source.Infos {
fname := filepath.Join(t.sourcePath, src.Filename)
t.sourceMap.Put(ctx, fname, src.Data)
}
t.ops = make(map[digest.Digest]*pb.Op, len(t.def.Def))
for _, dt := range t.def.Def {
dgst := digest.FromBytes(dt)
var op pb.Op
if err := op.UnmarshalVT(dt); err != nil {
return err
}
t.ops[dgst] = &op
}
t.head, err = t.def.Head()
return err
}
func (t *thread) findBacklinks() map[digest.Digest]map[digest.Digest]struct{} {
backlinks := make(map[digest.Digest]map[digest.Digest]struct{})
for dgst := range t.ops {
backlinks[dgst] = make(map[digest.Digest]struct{})
}
for dgst, op := range t.ops {
for _, inp := range op.Inputs {
if digest.Digest(inp.Digest) == t.head {
continue
}
backlinks[digest.Digest(inp.Digest)][dgst] = struct{}{}
}
}
return backlinks
}
func (t *thread) createRegions(ctx Context) error {
if err := t.getLLBState(ctx); err != nil {
return err
}
// Find the links going from inputs to their outputs.
// This isn't represented in the LLB graph but we need it to ensure
// an op only has one child and whether we are allowed to visit a node.
backlinks := t.findBacklinks()
// Create distinct regions whenever we have any branch (inputs or outputs).
t.regions = []*region{}
t.regionsByDigest = map[digest.Digest]int{}
determineRegion := func(dgst digest.Digest, children map[digest.Digest]struct{}) {
if len(children) == 1 {
var cDgst digest.Digest
for d := range children {
cDgst = d
}
childOp := t.ops[cDgst]
if len(childOp.Inputs) == 1 {
// We have one child and our child has one input so we can be merged
// into the same region as our child.
region := t.regionsByDigest[cDgst]
t.regions[region].digests = append(t.regions[region].digests, dgst)
t.regionsByDigest[dgst] = region
return
}
}
// We will require a new region for this digest because
// we weren't able to merge it in within the existing regions.
next := len(t.regions)
t.regions = append(t.regions, &region{
digests: []digest.Digest{dgst},
dependsOn: make(map[int]struct{}),
})
t.regionsByDigest[dgst] = next
// Mark each child as depending on this new region.
for child := range children {
region := t.regionsByDigest[child]
t.regions[region].dependsOn[next] = struct{}{}
}
}
canVisit := func(dgst digest.Digest) bool {
for dgst := range backlinks[dgst] {
if _, ok := t.regionsByDigest[dgst]; !ok {
// One of our outputs has not been categorized.
return false
}
}
return true
}
unvisited := []digest.Digest{t.head}
for len(unvisited) > 0 {
dgst := pop(&unvisited)
op := t.ops[dgst]
children := backlinks[dgst]
determineRegion(dgst, children)
// Determine which inputs we can now visit.
for _, inp := range op.Inputs {
indgst := digest.Digest(inp.Digest)
if canVisit(indgst) {
unvisited = append(unvisited, indgst)
}
}
}
// Reverse each of the digests so dependencies are first.
// It is currently in reverse topological order and it needs to be in
// topological order.
for _, r := range t.regions {
slices.Reverse(r.digests)
}
t.propagateRegionDependencies()
return nil
}
// propagateRegionDependencies will propagate the dependsOn attribute between
// different regions to make dependency lookups easier. If A depends on B
// and B depends on C, then A depends on C. But the algorithm before this will only
// record direct dependencies.
func (t *thread) propagateRegionDependencies() {
for _, r := range t.regions {
for {
n := len(r.dependsOn)
for i := range r.dependsOn {
for j := range t.regions[i].dependsOn {
r.dependsOn[j] = struct{}{}
}
}
if n == len(r.dependsOn) {
break
}
}
}
}
func (t *thread) seekNext(ctx Context, step stepType) (digest.Digest, error) {
// If we're at the end, return no digest to signal that
// we should conclude debugging.
if t.curPos == t.head {
return "", nil
}
target := t.head
if step == stepNext {
target = t.nextDigest()
}
if target == "" {
return "", nil
}
return t.seek(ctx, target)
}
func (t *thread) seek(ctx Context, target digest.Digest) (digest.Digest, error) {
ref, err := t.solve(ctx, target)
if err != nil {
return "", err
}
if err = ref.Evaluate(ctx); err != nil {
var solveErr *errdefs.SolveError
if errors.As(err, &solveErr) {
if dt, err := solveErr.Op.MarshalVT(); err == nil {
t.curPos = digest.FromBytes(dt)
}
} else {
t.curPos = ""
}
} else {
t.curPos = target
}
return t.curPos, err
}
func (t *thread) nextDigest() digest.Digest {
// If we have no position, automatically select the first step.
if t.curPos == "" {
r := t.regions[len(t.regions)-1]
return r.digests[0]
}
// Look up the region associated with our current position.
// If we can't find it, just pretend we're using step continue.
region, ok := t.regionsByDigest[t.curPos]
if !ok {
return t.head
}
r := t.regions[region]
i := slices.Index(r.digests, t.curPos) + 1
for {
if i >= len(r.digests) {
if region <= 0 {
// We're at the end of our execution. Should have been caught by
// t.head == t.curPos.
return ""
}
region--
r = t.regions[region]
i = 0
continue
}
next := r.digests[i]
if loc, ok := t.def.Source.Locations[string(next)]; !ok || len(loc.Locations) == 0 {
// Skip this digest because it has no locations in the source file.
i++
continue
}
return next
}
}
func (t *thread) solve(ctx context.Context, target digest.Digest) (gateway.Reference, error) {
if target == t.head {
return t.ref, nil
}
head := &pb.Op{
Inputs: []*pb.Input{{Digest: string(target)}},
}
dt, err := head.MarshalVT()
if err != nil {
return nil, err
}
def := t.def.ToPB()
def.Def[len(def.Def)-1] = dt
res, err := t.c.Solve(ctx, gateway.SolveRequest{
Definition: def,
})
if err != nil {
return nil, err
}
return res.SingleRef()
}
func (t *thread) newStackFrame() dap.StackFrame {
return dap.StackFrame{
Id: int(t.idPool.Get()),
}
}
func (t *thread) makeStackTrace() []dap.StackFrame {
var frames []dap.StackFrame
region := t.regionsByDigest[t.curPos]
r := t.regions[region]
digests := r.digests
if index := slices.Index(digests, t.curPos); index >= 0 {
digests = digests[:index+1]
}
for i := len(digests) - 1; i >= 0; i-- {
dgst := digests[i]
frame := t.newStackFrame()
if meta, ok := t.def.Metadata[dgst]; ok {
fillStackFrameMetadata(&frame, meta)
}
if loc, ok := t.def.Source.Locations[string(dgst)]; ok {
t.fillStackFrameLocation(&frame, loc)
}
frames = append(frames, frame)
}
return frames
}
func fillStackFrameMetadata(frame *dap.StackFrame, meta llb.OpMetadata) {
if name, ok := meta.Description["llb.customname"]; ok {
frame.Name = name
} else if cmd, ok := meta.Description["com.docker.dockerfile.v1.command"]; ok {
frame.Name = cmd
}
// TODO: should we infer the name from somewhere else?
}
func (t *thread) fillStackFrameLocation(frame *dap.StackFrame, loc *pb.Locations) {
for _, l := range loc.Locations {
for _, r := range l.Ranges {
frame.Line = int(r.Start.Line)
frame.Column = int(r.Start.Character)
frame.EndLine = int(r.End.Line)
frame.EndColumn = int(r.End.Character)
info := t.def.Source.Infos[l.SourceIndex]
frame.Source = &dap.Source{
Path: filepath.Join(t.sourcePath, info.Filename),
}
return
}
}
}
func pop[S ~[]E, E any](s *S) E {
e := (*s)[len(*s)-1]
*s = (*s)[:len(*s)-1]
return e
}
+1 -1
View File
@@ -57,7 +57,7 @@ func (m *Monitor) Handler() build.Handler {
}
}
func (m *Monitor) Evaluate(ctx context.Context, _ string, c gateway.Client, res *gateway.Result) error {
func (m *Monitor) Evaluate(ctx context.Context, _ string, c gateway.Client, res *gateway.Result, _ build.Options) error {
buildErr := res.EachRef(func(ref gateway.Reference) error {
return ref.Evaluate(ctx)
})