dag: replace dag.Walk with our walker
This commit is contained in:
Mitchell Hashimoto
parent
b1aa6fd598
commit
28fff99ea8
94
dag/dag.go
94
dag/dag.go
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@ -2,11 +2,8 @@ package dag
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import (
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"fmt"
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"log"
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"sort"
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"strings"
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"sync"
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"time"
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"github.com/hashicorp/go-multierror"
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)
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@ -169,94 +166,9 @@ func (g *AcyclicGraph) Cycles() [][]Vertex {
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func (g *AcyclicGraph) Walk(cb WalkFunc) error {
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defer g.debug.BeginOperation(typeWalk, "").End("")
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// Cache the vertices since we use it multiple times
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vertices := g.Vertices()
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// Build the waitgroup that signals when we're done
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var wg sync.WaitGroup
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wg.Add(len(vertices))
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doneCh := make(chan struct{})
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go func() {
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defer close(doneCh)
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wg.Wait()
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}()
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// The map of channels to watch to wait for vertices to finish
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vertMap := make(map[Vertex]chan struct{})
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for _, v := range vertices {
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vertMap[v] = make(chan struct{})
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}
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// The map of whether a vertex errored or not during the walk
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var errLock sync.Mutex
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var errs error
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errMap := make(map[Vertex]bool)
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for _, v := range vertices {
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// Build our list of dependencies and the list of channels to
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// wait on until we start executing for this vertex.
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deps := AsVertexList(g.DownEdges(v))
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depChs := make([]<-chan struct{}, len(deps))
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for i, dep := range deps {
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depChs[i] = vertMap[dep]
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}
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// Get our channel so that we can close it when we're done
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ourCh := vertMap[v]
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// Start the goroutine to wait for our dependencies
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readyCh := make(chan bool)
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go func(v Vertex, deps []Vertex, chs []<-chan struct{}, readyCh chan<- bool) {
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// First wait for all the dependencies
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for i, ch := range chs {
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DepSatisfied:
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for {
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select {
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case <-ch:
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break DepSatisfied
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case <-time.After(time.Second * 5):
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log.Printf("[DEBUG] vertex %q, waiting for: %q",
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VertexName(v), VertexName(deps[i]))
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}
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}
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log.Printf("[DEBUG] vertex %q, got dep: %q",
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VertexName(v), VertexName(deps[i]))
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}
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// Then, check the map to see if any of our dependencies failed
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errLock.Lock()
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defer errLock.Unlock()
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for _, dep := range deps {
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if errMap[dep] {
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errMap[v] = true
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readyCh <- false
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return
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}
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}
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readyCh <- true
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}(v, deps, depChs, readyCh)
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// Start the goroutine that executes
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go func(v Vertex, doneCh chan<- struct{}, readyCh <-chan bool) {
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defer close(doneCh)
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defer wg.Done()
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var err error
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if ready := <-readyCh; ready {
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err = cb(v)
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}
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errLock.Lock()
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defer errLock.Unlock()
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if err != nil {
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errMap[v] = true
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errs = multierror.Append(errs, err)
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}
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}(v, ourCh, readyCh)
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}
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<-doneCh
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return errs
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w := &walker{Callback: cb, Reverse: true}
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w.Update(g.vertices, g.edges)
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return w.Wait()
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}
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// simple convenience helper for converting a dag.Set to a []Vertex
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118
dag/walk.go
118
dag/walk.go
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@ -1,6 +1,7 @@
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package dag
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import (
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"errors"
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"fmt"
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"log"
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"sync"
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@ -12,6 +13,9 @@ import (
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// walker performs a graph walk and supports walk-time changing of vertices
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// and edges.
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//
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// The walk is depth first by default. This can be changed with the Reverse
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// option.
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//
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// A single walker is only valid for one graph walk. After the walk is complete
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// you must construct a new walker to walk again. State for the walk is never
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// deleted in case vertices or edges are changed.
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@ -19,6 +23,10 @@ type walker struct {
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// Callback is what is called for each vertex
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Callback WalkFunc
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// Reverse, if true, causes the source of an edge to depend on a target.
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// When false (default), the target depends on the source.
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Reverse bool
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// changeLock must be held to modify any of the fields below. Only Update
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// should modify these fields. Modifying them outside of Update can cause
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// serious problems.
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@ -44,7 +52,7 @@ type walkerVertex struct {
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// Dependency information. Any changes to any of these fields requires
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// holding DepsLock.
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DepsCh chan struct{}
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DepsCh chan bool
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DepsUpdateCh chan struct{}
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DepsLock sync.Mutex
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@ -54,6 +62,11 @@ type walkerVertex struct {
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depsCancelCh chan struct{}
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}
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// errWalkUpstream is used in the errMap of a walk to note that an upstream
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// dependency failed so this vertex wasn't run. This is not shown in the final
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// user-returned error.
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var errWalkUpstream = errors.New("upstream dependency failed")
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// Wait waits for the completion of the walk and returns any errors (
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// in the form of a multierror) that occurred. Update should be called
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// to populate the walk with vertices and edges prior to calling this.
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@ -72,8 +85,10 @@ func (w *walker) Wait() error {
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// Build the error
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var result error
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for v, err := range w.errMap {
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result = multierror.Append(result, fmt.Errorf(
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"%s: %s", VertexName(v), err))
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if err != nil && err != errWalkUpstream {
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result = multierror.Append(result, fmt.Errorf(
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"%s: %s", VertexName(v), err))
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}
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}
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return result
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@ -116,12 +131,12 @@ func (w *walker) Update(v, e *Set) {
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info := &walkerVertex{
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DoneCh: make(chan struct{}),
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CancelCh: make(chan struct{}),
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DepsCh: make(chan struct{}),
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DepsCh: make(chan bool, 1),
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deps: make(map[Vertex]chan struct{}),
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}
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// Close the deps channel immediately so it passes
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close(info.DepsCh)
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// Pass dependencies immediately assuming we have no edges
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info.DepsCh <- true
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// Add it to the map and kick off the walk
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w.vertexMap[v] = info
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@ -153,12 +168,7 @@ func (w *walker) Update(v, e *Set) {
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var changedDeps Set
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for _, raw := range newEdges.List() {
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edge := raw.(Edge)
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// waiter is the vertex that is "waiting" on this edge
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waiter := edge.Target()
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// dep is the dependency we're waiting on
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dep := edge.Source()
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waiter, dep := w.edgeParts(edge)
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// Get the info for the waiter
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waiterInfo, ok := w.vertexMap[waiter]
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@ -189,12 +199,7 @@ func (w *walker) Update(v, e *Set) {
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// Process reoved edges
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for _, raw := range oldEdges.List() {
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edge := raw.(Edge)
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// waiter is the vertex that is "waiting" on this edge
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waiter := edge.Target()
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// dep is the dependency we're waiting on
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dep := edge.Source()
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waiter, dep := w.edgeParts(edge)
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// Get the info for the waiter
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waiterInfo, ok := w.vertexMap[waiter]
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@ -226,7 +231,7 @@ func (w *walker) Update(v, e *Set) {
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}
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// Create a new done channel
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doneCh := make(chan struct{})
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doneCh := make(chan bool, 1)
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// Create the channel we close for cancellation
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cancelCh := make(chan struct{})
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@ -252,6 +257,10 @@ func (w *walker) Update(v, e *Set) {
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}
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info.depsCancelCh = cancelCh
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log.Printf(
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"[DEBUG] dag/walk: dependencies changed for %q, sending new deps",
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VertexName(v))
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// Start the waiter
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go w.waitDeps(v, deps, doneCh, cancelCh)
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}
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@ -264,6 +273,16 @@ func (w *walker) Update(v, e *Set) {
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}
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}
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// edgeParts returns the waiter and the dependency, in that order.
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// The waiter is waiting on the dependency.
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func (w *walker) edgeParts(e Edge) (Vertex, Vertex) {
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if w.Reverse {
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return e.Source(), e.Target()
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}
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return e.Target(), e.Source()
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}
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// walkVertex walks a single vertex, waiting for any dependencies before
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// executing the callback.
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func (w *walker) walkVertex(v Vertex, info *walkerVertex) {
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@ -273,16 +292,20 @@ func (w *walker) walkVertex(v Vertex, info *walkerVertex) {
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// When we're done, always close our done channel
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defer close(info.DoneCh)
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// Wait for our dependencies
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depsCh := info.DepsCh
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// Wait for our dependencies. We create a [closed] deps channel so
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// that we can immediately fall through to load our actual DepsCh.
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var depsSuccess bool
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depsCh := make(chan bool, 1)
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depsCh <- true
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close(depsCh)
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for {
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select {
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case <-info.CancelCh:
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// Cancel
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return
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case <-depsCh:
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// Deps complete!
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case depsSuccess = <-depsCh:
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// Deps complete! Mark as nil to trigger completion handling.
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depsCh = nil
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case <-info.DepsUpdateCh:
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@ -306,9 +329,27 @@ func (w *walker) walkVertex(v Vertex, info *walkerVertex) {
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}
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}
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// Call our callback
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log.Printf("[DEBUG] dag/walk: walking %q", VertexName(v))
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if err := w.Callback(v); err != nil {
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// If we passed dependencies, we just want to check once more that
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// we're not cancelled, since this can happen just as dependencies pass.
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select {
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case <-info.CancelCh:
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// Cancelled during an update while dependencies completed.
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return
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default:
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}
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// Run our callback or note that our upstream failed
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var err error
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if depsSuccess {
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log.Printf("[DEBUG] dag/walk: walking %q", VertexName(v))
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err = w.Callback(v)
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} else {
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log.Printf("[DEBUG] dag/walk: upstream errored, not walking %q", VertexName(v))
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err = errWalkUpstream
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}
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// Record the error
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if err != nil {
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w.errLock.Lock()
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defer w.errLock.Unlock()
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@ -322,11 +363,8 @@ func (w *walker) walkVertex(v Vertex, info *walkerVertex) {
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func (w *walker) waitDeps(
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v Vertex,
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deps map[Vertex]<-chan struct{},
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doneCh chan<- struct{},
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doneCh chan<- bool,
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cancelCh <-chan struct{}) {
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// Whenever we return, mark ourselves as complete
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defer close(doneCh)
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// For each dependency given to us, wait for it to complete
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for dep, depCh := range deps {
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DepSatisfied:
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@ -337,13 +375,29 @@ func (w *walker) waitDeps(
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break DepSatisfied
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case <-cancelCh:
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// Wait cancelled
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// Wait cancelled. Note that we didn't satisfy dependencies
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// so that anything waiting on us also doesn't run.
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doneCh <- false
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return
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case <-time.After(time.Second * 5):
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log.Printf("[DEBUG] vertex %q, waiting for: %q",
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log.Printf("[DEBUG] dag/walk: vertex %q, waiting for: %q",
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VertexName(v), VertexName(dep))
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}
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}
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}
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// Dependencies satisfied! We need to check if any errored
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w.errLock.Lock()
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defer w.errLock.Unlock()
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for dep, _ := range deps {
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if w.errMap[dep] != nil {
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// One of our dependencies failed, so return false
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doneCh <- false
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return
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}
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}
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// All dependencies satisfied and successful
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doneCh <- true
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}
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@ -33,6 +33,44 @@ func TestWalker_basic(t *testing.T) {
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}
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}
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func TestWalker_error(t *testing.T) {
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var g Graph
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g.Add(1)
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g.Add(2)
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g.Add(3)
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g.Add(4)
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g.Connect(BasicEdge(1, 2))
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g.Connect(BasicEdge(2, 3))
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g.Connect(BasicEdge(3, 4))
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// Record function
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var order []interface{}
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recordF := walkCbRecord(&order)
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// Build a callback that delays until we close a channel
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cb := func(v Vertex) error {
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if v == 2 {
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return fmt.Errorf("error!")
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}
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return recordF(v)
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}
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w := &walker{Callback: cb}
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w.Update(g.vertices, g.edges)
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// Wait
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if err := w.Wait(); err == nil {
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t.Fatal("expect error")
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}
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// Check
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expected := []interface{}{1}
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if !reflect.DeepEqual(order, expected) {
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t.Fatalf("bad: %#v", order)
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}
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}
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func TestWalker_newVertex(t *testing.T) {
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// Run it a bunch of times since it is timing dependent
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for i := 0; i < 50; i++ {
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@ -82,26 +120,20 @@ func TestWalker_removeVertex(t *testing.T) {
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recordF := walkCbRecord(&order)
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// Build a callback that delays until we close a channel
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gateCh := make(chan struct{})
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var w *walker
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cb := func(v Vertex) error {
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if v == 1 {
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<-gateCh
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g.Remove(2)
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w.Update(g.vertices, g.edges)
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}
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return recordF(v)
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}
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// Add the initial vertices
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w := &walker{Callback: cb}
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w = &walker{Callback: cb}
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w.Update(g.vertices, g.edges)
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// Remove a vertex
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g.Remove(2)
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w.Update(g.vertices, g.edges)
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// Open gate
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close(gateCh)
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// Wait
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if err := w.Wait(); err != nil {
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t.Fatalf("err: %s", err)
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