Stop machine monitoring on Session shutdown

exec/bigmachine.go

@@ -122,6 +122,9 @@ type bigmachineExecutor struct {
 	// If the task is marked as exclusive, then one is added to their
 	// manager index.
 	managers []*machineManager
+
+	shutdownc  chan struct{}
+	managersWG sync.WaitGroup
 }
 
 func newBigmachineExecutor(system bigmachine.System, params ...bigmachine.Param) *bigmachineExecutor {
@@ -150,13 +153,23 @@ func (b *bigmachineExecutor) Start(sess *Session) (shutdown func()) {
 	b.worker = &worker{
 		MachineCombiners: sess.machineCombiners,
 	}
+	b.shutdownc = make(chan struct{})
 
-	return b.b.Shutdown
+	return func() {
+		close(b.shutdownc)
+		b.managersWG.Wait()
+		b.b.Shutdown()
+	}
 }
 
 func (b *bigmachineExecutor) manager(i int) *machineManager {
 	b.mu.Lock()
 	defer b.mu.Unlock()
+	ctx, cancel := context.WithCancel(backgroundcontext.Get())
+	go func() {
+		<-b.shutdownc
+		cancel()
+	}()
 	for i >= len(b.managers) {
 		b.managers = append(b.managers, nil)
 	}
@@ -168,7 +181,13 @@ func (b *bigmachineExecutor) manager(i int) *machineManager {
 			maxLoad = 0
 		}
 		b.managers[i] = newMachineManager(b.b, b.params, b.status, b.sess.Parallelism(), maxLoad, b.worker)
-		go b.managers[i].Do(backgroundcontext.Get())
+
+		b.managersWG.Add(1)
+		go func() {
+			b.managers[i].Do(ctx)
+			b.managers[i].machinesWG.Wait()
+			b.managersWG.Done()
+		}()
 	}
 	return b.managers[i]
 }

exec/slicemachine.go

@@ -11,7 +11,6 @@ import (
 	"sync"
 	"time"
 
-	"github.com/grailbio/base/backgroundcontext"
 	"github.com/grailbio/base/data"
 	"github.com/grailbio/base/errors"
 	"github.com/grailbio/base/log"
@@ -350,6 +349,8 @@ type machineManager struct {
 	schedQ   scheduleRequestQ
 	schedc   chan scheduleRequest
 	unschedc chan scheduleRequest
+
+	machinesWG sync.WaitGroup
 }
 
 // NewMachineManager returns a new machineManager paramterized by the
@@ -549,6 +550,14 @@ func (m *machineManager) Do(ctx context.Context) {
 				have/m.machprocs, have, pending/m.machprocs, pending)
 			go func() {
 				machines := startMachines(ctx, m.b, m.group, m.machprocs, needMachines, m.worker, m.params...)
+				for _, machine := range machines {
+					machine := machine
+					m.machinesWG.Add(1)
+					go func() {
+						machine.Go(ctx)
+						m.machinesWG.Done()
+					}()
+				}
 				startc <- startResult{
 					machines:  machines,
 					nFailures: needMachines - len(machines),
@@ -636,9 +645,6 @@ func startMachines(ctx context.Context, b *bigmachine.B, group *status.Group, ma
 				Status:       status,
 				maxTaskProcs: maxTaskProcs,
 			}
-			// TODO(marius): pass a context that's tied to the evaluation
-			// lifetime, or lifetime of the machine.
-			go sm.Go(backgroundcontext.Get())
 			slicemachines[i] = sm
 		}()
 	}