dag: replace dag.Walk with our walker

This commit is contained in:
Mitchell Hashimoto 2017-02-03 11:04:39 +01:00
parent b1aa6fd598
commit 28fff99ea8
No known key found for this signature in database
GPG Key ID: 744E147AA52F5B0A
3 changed files with 131 additions and 133 deletions

View File

@ -2,11 +2,8 @@ package dag
import (
"fmt"
"log"
"sort"
"strings"
"sync"
"time"
"github.com/hashicorp/go-multierror"
)
@ -169,94 +166,9 @@ func (g *AcyclicGraph) Cycles() [][]Vertex {
func (g *AcyclicGraph) Walk(cb WalkFunc) error {
defer g.debug.BeginOperation(typeWalk, "").End("")
// Cache the vertices since we use it multiple times
vertices := g.Vertices()
// Build the waitgroup that signals when we're done
var wg sync.WaitGroup
wg.Add(len(vertices))
doneCh := make(chan struct{})
go func() {
defer close(doneCh)
wg.Wait()
}()
// The map of channels to watch to wait for vertices to finish
vertMap := make(map[Vertex]chan struct{})
for _, v := range vertices {
vertMap[v] = make(chan struct{})
}
// The map of whether a vertex errored or not during the walk
var errLock sync.Mutex
var errs error
errMap := make(map[Vertex]bool)
for _, v := range vertices {
// Build our list of dependencies and the list of channels to
// wait on until we start executing for this vertex.
deps := AsVertexList(g.DownEdges(v))
depChs := make([]<-chan struct{}, len(deps))
for i, dep := range deps {
depChs[i] = vertMap[dep]
}
// Get our channel so that we can close it when we're done
ourCh := vertMap[v]
// Start the goroutine to wait for our dependencies
readyCh := make(chan bool)
go func(v Vertex, deps []Vertex, chs []<-chan struct{}, readyCh chan<- bool) {
// First wait for all the dependencies
for i, ch := range chs {
DepSatisfied:
for {
select {
case <-ch:
break DepSatisfied
case <-time.After(time.Second * 5):
log.Printf("[DEBUG] vertex %q, waiting for: %q",
VertexName(v), VertexName(deps[i]))
}
}
log.Printf("[DEBUG] vertex %q, got dep: %q",
VertexName(v), VertexName(deps[i]))
}
// Then, check the map to see if any of our dependencies failed
errLock.Lock()
defer errLock.Unlock()
for _, dep := range deps {
if errMap[dep] {
errMap[v] = true
readyCh <- false
return
}
}
readyCh <- true
}(v, deps, depChs, readyCh)
// Start the goroutine that executes
go func(v Vertex, doneCh chan<- struct{}, readyCh <-chan bool) {
defer close(doneCh)
defer wg.Done()
var err error
if ready := <-readyCh; ready {
err = cb(v)
}
errLock.Lock()
defer errLock.Unlock()
if err != nil {
errMap[v] = true
errs = multierror.Append(errs, err)
}
}(v, ourCh, readyCh)
}
<-doneCh
return errs
w := &walker{Callback: cb, Reverse: true}
w.Update(g.vertices, g.edges)
return w.Wait()
}
// simple convenience helper for converting a dag.Set to a []Vertex

View File

@ -1,6 +1,7 @@
package dag
import (
"errors"
"fmt"
"log"
"sync"
@ -12,6 +13,9 @@ import (
// walker performs a graph walk and supports walk-time changing of vertices
// and edges.
//
// The walk is depth first by default. This can be changed with the Reverse
// option.
//
// A single walker is only valid for one graph walk. After the walk is complete
// you must construct a new walker to walk again. State for the walk is never
// deleted in case vertices or edges are changed.
@ -19,6 +23,10 @@ type walker struct {
// Callback is what is called for each vertex
Callback WalkFunc
// Reverse, if true, causes the source of an edge to depend on a target.
// When false (default), the target depends on the source.
Reverse bool
// changeLock must be held to modify any of the fields below. Only Update
// should modify these fields. Modifying them outside of Update can cause
// serious problems.
@ -44,7 +52,7 @@ type walkerVertex struct {
// Dependency information. Any changes to any of these fields requires
// holding DepsLock.
DepsCh chan struct{}
DepsCh chan bool
DepsUpdateCh chan struct{}
DepsLock sync.Mutex
@ -54,6 +62,11 @@ type walkerVertex struct {
depsCancelCh chan struct{}
}
// errWalkUpstream is used in the errMap of a walk to note that an upstream
// dependency failed so this vertex wasn't run. This is not shown in the final
// user-returned error.
var errWalkUpstream = errors.New("upstream dependency failed")
// Wait waits for the completion of the walk and returns any errors (
// in the form of a multierror) that occurred. Update should be called
// to populate the walk with vertices and edges prior to calling this.
@ -72,8 +85,10 @@ func (w *walker) Wait() error {
// Build the error
var result error
for v, err := range w.errMap {
result = multierror.Append(result, fmt.Errorf(
"%s: %s", VertexName(v), err))
if err != nil && err != errWalkUpstream {
result = multierror.Append(result, fmt.Errorf(
"%s: %s", VertexName(v), err))
}
}
return result
@ -116,12 +131,12 @@ func (w *walker) Update(v, e *Set) {
info := &walkerVertex{
DoneCh: make(chan struct{}),
CancelCh: make(chan struct{}),
DepsCh: make(chan struct{}),
DepsCh: make(chan bool, 1),
deps: make(map[Vertex]chan struct{}),
}
// Close the deps channel immediately so it passes
close(info.DepsCh)
// Pass dependencies immediately assuming we have no edges
info.DepsCh <- true
// Add it to the map and kick off the walk
w.vertexMap[v] = info
@ -153,12 +168,7 @@ func (w *walker) Update(v, e *Set) {
var changedDeps Set
for _, raw := range newEdges.List() {
edge := raw.(Edge)
// waiter is the vertex that is "waiting" on this edge
waiter := edge.Target()
// dep is the dependency we're waiting on
dep := edge.Source()
waiter, dep := w.edgeParts(edge)
// Get the info for the waiter
waiterInfo, ok := w.vertexMap[waiter]
@ -189,12 +199,7 @@ func (w *walker) Update(v, e *Set) {
// Process reoved edges
for _, raw := range oldEdges.List() {
edge := raw.(Edge)
// waiter is the vertex that is "waiting" on this edge
waiter := edge.Target()
// dep is the dependency we're waiting on
dep := edge.Source()
waiter, dep := w.edgeParts(edge)
// Get the info for the waiter
waiterInfo, ok := w.vertexMap[waiter]
@ -226,7 +231,7 @@ func (w *walker) Update(v, e *Set) {
}
// Create a new done channel
doneCh := make(chan struct{})
doneCh := make(chan bool, 1)
// Create the channel we close for cancellation
cancelCh := make(chan struct{})
@ -252,6 +257,10 @@ func (w *walker) Update(v, e *Set) {
}
info.depsCancelCh = cancelCh
log.Printf(
"[DEBUG] dag/walk: dependencies changed for %q, sending new deps",
VertexName(v))
// Start the waiter
go w.waitDeps(v, deps, doneCh, cancelCh)
}
@ -264,6 +273,16 @@ func (w *walker) Update(v, e *Set) {
}
}
// edgeParts returns the waiter and the dependency, in that order.
// The waiter is waiting on the dependency.
func (w *walker) edgeParts(e Edge) (Vertex, Vertex) {
if w.Reverse {
return e.Source(), e.Target()
}
return e.Target(), e.Source()
}
// walkVertex walks a single vertex, waiting for any dependencies before
// executing the callback.
func (w *walker) walkVertex(v Vertex, info *walkerVertex) {
@ -273,16 +292,20 @@ func (w *walker) walkVertex(v Vertex, info *walkerVertex) {
// When we're done, always close our done channel
defer close(info.DoneCh)
// Wait for our dependencies
depsCh := info.DepsCh
// Wait for our dependencies. We create a [closed] deps channel so
// that we can immediately fall through to load our actual DepsCh.
var depsSuccess bool
depsCh := make(chan bool, 1)
depsCh <- true
close(depsCh)
for {
select {
case <-info.CancelCh:
// Cancel
return
case <-depsCh:
// Deps complete!
case depsSuccess = <-depsCh:
// Deps complete! Mark as nil to trigger completion handling.
depsCh = nil
case <-info.DepsUpdateCh:
@ -306,9 +329,27 @@ func (w *walker) walkVertex(v Vertex, info *walkerVertex) {
}
}
// Call our callback
log.Printf("[DEBUG] dag/walk: walking %q", VertexName(v))
if err := w.Callback(v); err != nil {
// If we passed dependencies, we just want to check once more that
// we're not cancelled, since this can happen just as dependencies pass.
select {
case <-info.CancelCh:
// Cancelled during an update while dependencies completed.
return
default:
}
// Run our callback or note that our upstream failed
var err error
if depsSuccess {
log.Printf("[DEBUG] dag/walk: walking %q", VertexName(v))
err = w.Callback(v)
} else {
log.Printf("[DEBUG] dag/walk: upstream errored, not walking %q", VertexName(v))
err = errWalkUpstream
}
// Record the error
if err != nil {
w.errLock.Lock()
defer w.errLock.Unlock()
@ -322,11 +363,8 @@ func (w *walker) walkVertex(v Vertex, info *walkerVertex) {
func (w *walker) waitDeps(
v Vertex,
deps map[Vertex]<-chan struct{},
doneCh chan<- struct{},
doneCh chan<- bool,
cancelCh <-chan struct{}) {
// Whenever we return, mark ourselves as complete
defer close(doneCh)
// For each dependency given to us, wait for it to complete
for dep, depCh := range deps {
DepSatisfied:
@ -337,13 +375,29 @@ func (w *walker) waitDeps(
break DepSatisfied
case <-cancelCh:
// Wait cancelled
// Wait cancelled. Note that we didn't satisfy dependencies
// so that anything waiting on us also doesn't run.
doneCh <- false
return
case <-time.After(time.Second * 5):
log.Printf("[DEBUG] vertex %q, waiting for: %q",
log.Printf("[DEBUG] dag/walk: vertex %q, waiting for: %q",
VertexName(v), VertexName(dep))
}
}
}
// Dependencies satisfied! We need to check if any errored
w.errLock.Lock()
defer w.errLock.Unlock()
for dep, _ := range deps {
if w.errMap[dep] != nil {
// One of our dependencies failed, so return false
doneCh <- false
return
}
}
// All dependencies satisfied and successful
doneCh <- true
}

View File

@ -33,6 +33,44 @@ func TestWalker_basic(t *testing.T) {
}
}
func TestWalker_error(t *testing.T) {
var g Graph
g.Add(1)
g.Add(2)
g.Add(3)
g.Add(4)
g.Connect(BasicEdge(1, 2))
g.Connect(BasicEdge(2, 3))
g.Connect(BasicEdge(3, 4))
// Record function
var order []interface{}
recordF := walkCbRecord(&order)
// Build a callback that delays until we close a channel
cb := func(v Vertex) error {
if v == 2 {
return fmt.Errorf("error!")
}
return recordF(v)
}
w := &walker{Callback: cb}
w.Update(g.vertices, g.edges)
// Wait
if err := w.Wait(); err == nil {
t.Fatal("expect error")
}
// Check
expected := []interface{}{1}
if !reflect.DeepEqual(order, expected) {
t.Fatalf("bad: %#v", order)
}
}
func TestWalker_newVertex(t *testing.T) {
// Run it a bunch of times since it is timing dependent
for i := 0; i < 50; i++ {
@ -82,26 +120,20 @@ func TestWalker_removeVertex(t *testing.T) {
recordF := walkCbRecord(&order)
// Build a callback that delays until we close a channel
gateCh := make(chan struct{})
var w *walker
cb := func(v Vertex) error {
if v == 1 {
<-gateCh
g.Remove(2)
w.Update(g.vertices, g.edges)
}
return recordF(v)
}
// Add the initial vertices
w := &walker{Callback: cb}
w = &walker{Callback: cb}
w.Update(g.vertices, g.edges)
// Remove a vertex
g.Remove(2)
w.Update(g.vertices, g.edges)
// Open gate
close(gateCh)
// Wait
if err := w.Wait(); err != nil {
t.Fatalf("err: %s", err)