fleetd: support conflict in global unit

Documentation/unit-files-and-scheduling.md

@@ -22,7 +22,7 @@ Note that these requirements are derived directly from systemd, with the only ex
 | `MachineOf` | Limit eligible machines to the one that hosts a specific unit. |
 | `MachineMetadata` | Limit eligible machines to those with this specific metadata. |
 | `Conflicts` | Prevent a unit from being collocated with other units using glob-matching on the other unit names. |
-| `Global` | Schedule this unit on all agents in the cluster. A unit is considered invalid if options other than `MachineMetadata` are provided alongside `Global=true`. |
+| `Global` | Schedule this unit on those agents in the cluster, which satisfy the conditions of both `MachineMetadata` and `Conflicts` if any of them is also given. A unit is considered invalid if options other than `MachineMetadata` and `Conflicts` are provided alongside `Global=true`. If `MachineMetadata` is provided alongside `Global=true`, only the agents having the metadata can be scheduled on. If `Conflicts` is provided alongside `Global=true`, only the agents not having the conflicting units can be scheduled on. The conflicting units also can not be scheduled on the agents which already have the existing conflicting global unit.|
 | `Replaces` | Schedule a specified unit on another machine. A unit is considered invalid if options `Global` or `Conflicts` are provided alongside `Replaces=`. A circular replacement between multiple units is not allowed. |
 
 See [more information][unit-scheduling] on these parameters and how they impact scheduling decisions.

agent/reconcile.go

@@ -142,16 +142,25 @@ func desiredAgentState(a *Agent, reg registry.Registry) (*AgentState, error) {
 	for _, u := range units {
 		u := u
 		md := u.RequiredTargetMetadata()
-		if u.IsGlobal() && !machine.HasMetadata(&ms, md) {
-			log.Debugf("Agent unable to run global unit %s: missing required metadata", u.Name)
-			continue
+
+		if u.IsGlobal() {
+			if !machine.HasMetadata(&ms, md) {
+				log.Debugf("Agent unable to run global unit %s: missing required metadata", u.Name)
+				continue
+			}
 		}
+
 		if !u.IsGlobal() {
 			sUnit, ok := sUnitMap[u.Name]
 			if !ok || sUnit.TargetMachineID == "" || sUnit.TargetMachineID != ms.ID {
 				continue
 			}
 		}
+
+		if cExists, _ := as.HasConflict(u.Name, u.Conflicts()); cExists {
+			continue
+		}
+
 		as.Units[u.Name] = &u
 	}
 

agent/state.go

@@ -39,8 +39,8 @@ func (as *AgentState) unitScheduled(name string) bool {
 	return as.Units[name] != nil
 }
 
-// hasConflict determines whether there are any known conflicts with the given Unit
-func (as *AgentState) hasConflict(pUnitName string, pConflicts []string) (found bool, conflict string) {
+// HasConflict determines whether there are any known conflicts with the given Unit
+func (as *AgentState) HasConflict(pUnitName string, pConflicts []string) (found bool, conflict string) {
 	for _, eUnit := range as.Units {
 		if pUnitName == eUnit.Name {
 			continue
@@ -145,7 +145,7 @@ func (as *AgentState) AbleToRun(j *job.Job) (bool, string) {
 		}
 	}
 
-	if cExists, cJobName := as.hasConflict(j.Name, j.Conflicts()); cExists {
+	if cExists, cJobName := as.HasConflict(j.Name, j.Conflicts()); cExists {
 		return false, fmt.Sprintf("found conflict with locally-scheduled Unit(%s)", cJobName)
 	}
 

agent/state_test.go

@@ -85,7 +85,7 @@ func TestHasConflicts(t *testing.T) {
 	}
 
 	for i, tt := range tests {
-		got, conflict := tt.cState.hasConflict(tt.job.Name, tt.job.Conflicts())
+		got, conflict := tt.cState.HasConflict(tt.job.Name, tt.job.Conflicts())
 		if got != tt.want {
 			var msg string
 			if tt.want == true {

api/units.go

@@ -259,8 +259,6 @@ func ValidateOptions(opts []*schema.UnitOption) error {
 		return errors.New("MachineID cannot be used with Replaces")
 	case isGlobal && hasPeers:
 		return errors.New("Global cannot be used with Peers")
-	case isGlobal && hasConflicts:
-		return errors.New("Global cannot be used with Conflicts")
 	case isGlobal && hasReplaces:
 		return errors.New("Global cannot be used with Replaces")
 	case hasConflicts && hasReplaces:

api/units_test.go

@@ -650,7 +650,7 @@ func TestValidateOptions(t *testing.T) {
 			},
 			true,
 		},
-		// Global with Peers/Conflicts no good
+		// Global with Conflicts is ok
 		{
 			[]*schema.UnitOption{
 				&schema.UnitOption{
@@ -660,7 +660,7 @@ func TestValidateOptions(t *testing.T) {
 				},
 				makeConflictUO("foo.service"),
 			},
-			false,
+			true,
 		},
 		{
 			[]*schema.UnitOption{
@@ -671,8 +671,9 @@ func TestValidateOptions(t *testing.T) {
 				},
 				makeConflictUO("bar.service"),
 			},
-			false,
+			true,
 		},
+		// Global with peer no good
 		{
 			[]*schema.UnitOption{
 				&schema.UnitOption{

engine/state.go

@@ -93,9 +93,14 @@ func (cs *clusterState) agents() map[string]*agent.AgentState {
 	for _, gu := range cs.gUnits {
 		gu := gu
 		for _, a := range agents {
-			if machine.HasMetadata(a.MState, gu.RequiredTargetMetadata()) {
-				a.Units[gu.Name] = gu
+			if !machine.HasMetadata(a.MState, gu.RequiredTargetMetadata()) {
+				continue
 			}
+
+			if cExists, _ := a.HasConflict(gu.Name, gu.Conflicts()); cExists {
+				continue
+			}
+			a.Units[gu.Name] = gu
 		}
 	}
 

fleetctl/fleetctl_test.go

@@ -325,12 +325,6 @@ MachineOf=zxcvq`),
 			"foo.service",
 			newUnitFile(t, `[X-Fleet]
 Global=true
-Conflicts=bar`),
-		},
-		{
-			"foo.service",
-			newUnitFile(t, `[X-Fleet]
-Global=true
 Replaces=bar`),
 		},
 		{

functional/fixtures/units/conflict-global.0.service

@@ -0,0 +1,9 @@
+[Unit]
+Description=Test Unit
+
+[Service]
+ExecStart=/bin/bash -c "while true; do echo Hello, World!; sleep 1; done"
+
+[X-Fleet]
+Global=true
+Conflicts=conflict-global.*.service

functional/fixtures/units/conflict-global.1.service

@@ -0,0 +1,9 @@
+[Unit]
+Description=Test Unit
+
+[Service]
+ExecStart=/bin/bash -c "while true; do echo Hello, World!; sleep 1; done"
+
+[X-Fleet]
+Global=true
+Conflicts=conflict-global.*.service

functional/scheduling_test.go

@@ -582,3 +582,83 @@ func TestScheduleGlobalUnits(t *testing.T) {
 		}
 	}
 }
+
+// TestScheduleGlobalConflicts starts 2 global units that conflict with each
+// other, and check if only the first one can be found.
+func TestScheduleGlobalConflicts(t *testing.T) {
+	// Create a three-member cluster
+	cluster, err := platform.NewNspawnCluster("smoke")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer cluster.Destroy(t)
+	members, err := platform.CreateNClusterMembers(cluster, 3)
+	if err != nil {
+		t.Fatal(err)
+	}
+	m0 := members[0]
+	machines, err := cluster.WaitForNMachines(m0, 3)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	cfGlobal0 := "fixtures/units/conflict-global.0.service"
+	cfGlobal1 := "fixtures/units/conflict-global.1.service"
+
+	// Launch a global unit
+	stdout, stderr, err := cluster.Fleetctl(m0, "start", "--no-block", cfGlobal0)
+	if err != nil {
+		t.Fatalf("Failed starting units: \nstdout: %s\nstderr: %s\nerr: %v", stdout, stderr, err)
+	}
+
+	// the global unit should show up active on 3 machines
+	_, err = cluster.WaitForNActiveUnits(m0, 3)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Now add another global unit, which actually should not be started.
+	stdout, stderr, err = cluster.Fleetctl(m0, "start", "--no-block", cfGlobal1)
+	if err != nil {
+		t.Fatalf("Failed starting unit: \nstdout: %s\nstderr: %s\nerr: %v", stdout, stderr, err)
+	}
+
+	// Should see only 3 units
+	states, err := cluster.WaitForNActiveUnits(m0, 3)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Each machine should have a single global unit conflict-global.0.service,
+	// but not conflict-global.1.service.
+	us0 := states[path.Base(cfGlobal0)]
+	us1 := states[path.Base(cfGlobal1)]
+	for _, mach := range machines {
+		var found bool
+		for _, state := range us0 {
+			if state.Machine == mach {
+				found = true
+				break
+			}
+		}
+		if !found {
+			t.Fatalf("Did not find global unit on machine %v", mach)
+			t.Logf("Found unit states:")
+			for _, state := range states {
+				t.Logf("%#v", state)
+			}
+		}
+
+		found = false
+		for _, state := range us1 {
+			if state.Machine == mach {
+				found = true
+				break
+			}
+		}
+		if found {
+			t.Fatalf("Did find global unit %s on machine %v", us1, mach)
+			t.Logf("Global units were not conflicted as expected.")
+		}
+	}
+}