client: alloc diffing

client/util.go

@@ -4,10 +4,74 @@ import (
 	crand "crypto/rand"
 	"fmt"
 	"time"
+
+	"github.com/hashicorp/nomad/nomad/structs"
 )
 
 import "math/rand"
 
+type allocTuple struct {
+	exist, updated *structs.Allocation
+}
+
+// diffResult is used to return the sets that result from a diff
+type diffResult struct {
+	added   []*structs.Allocation
+	removed []*structs.Allocation
+	updated []allocTuple
+	ignore  []*structs.Allocation
+}
+
+func (d *diffResult) GoString() string {
+	return fmt.Sprintf("allocs: (added %d) (removed %d) (updated %d) (ignore %d)",
+		len(d.added), len(d.removed), len(d.updated), len(d.ignore))
+}
+
+// diffAllocs is used to diff the existing and updated allocations
+// to see what has happened.
+func diffAllocs(existing, updated []*structs.Allocation) *diffResult {
+	result := &diffResult{}
+
+	// Index the updated allocations by id
+	idx := make(map[string]*structs.Allocation)
+	for _, update := range updated {
+		idx[update.ID] = update
+	}
+
+	// Scan the existing allocations
+	existIdx := make(map[string]struct{})
+	for _, exist := range existing {
+		// Mark this as existing
+		existIdx[exist.ID] = struct{}{}
+
+		// Check for presence in the new set
+		update, ok := idx[exist.ID]
+
+		// If not present, removed
+		if !ok {
+			result.removed = append(result.removed, exist)
+			continue
+		}
+
+		// Check for an update
+		if update.ModifyIndex > exist.ModifyIndex {
+			result.updated = append(result.updated, allocTuple{exist, update})
+			continue
+		}
+
+		// Ignore this
+		result.ignore = append(result.ignore, exist)
+	}
+
+	// Scan the updated allocations for any that are new
+	for _, update := range updated {
+		if _, ok := existIdx[update.ID]; !ok {
+			result.added = append(result.added, update)
+		}
+	}
+	return result
+}
+
 // generateUUID is used to generate a random UUID
 func generateUUID() string {
 	buf := make([]byte, 16)

client/util_test.go

@@ -5,8 +5,50 @@ import (
 	"regexp"
 	"testing"
 	"time"
+
+	"github.com/hashicorp/nomad/nomad/mock"
+	"github.com/hashicorp/nomad/nomad/structs"
 )
 
+func TestDiffAllocs(t *testing.T) {
+	alloc1 := mock.Alloc() // Ignore
+	alloc2 := mock.Alloc() // Update
+	alloc2u := new(structs.Allocation)
+	*alloc2u = *alloc2
+	alloc2u.ModifyIndex += 1
+	alloc3 := mock.Alloc() // Remove
+	alloc4 := mock.Alloc() // Add
+
+	exist := []*structs.Allocation{
+		alloc1,
+		alloc2,
+		alloc3,
+	}
+	updated := []*structs.Allocation{
+		alloc1,
+		alloc2u,
+		alloc4,
+	}
+
+	result := diffAllocs(exist, updated)
+
+	if len(result.ignore) != 1 || result.ignore[0] != alloc1 {
+		t.Fatalf("Bad: %#v", result.ignore)
+	}
+	if len(result.added) != 1 || result.added[0] != alloc4 {
+		t.Fatalf("Bad: %#v", result.added)
+	}
+	if len(result.removed) != 1 || result.removed[0] != alloc3 {
+		t.Fatalf("Bad: %#v", result.removed)
+	}
+	if len(result.updated) != 1 {
+		t.Fatalf("Bad: %#v", result.updated)
+	}
+	if result.updated[0].exist != alloc2 || result.updated[0].updated != alloc2u {
+		t.Fatalf("Bad: %#v", result.updated)
+	}
+}
+
 func TestGenerateUUID(t *testing.T) {
 	prev := generateUUID()
 	for i := 0; i < 100; i++ {