replication: report a filesystem is active vs. blocked on something

- `BlockedOn` prop in JSON report
- Bring back the `*` in front of the filesystem report as an activity indicator.

fixes https://github.com/zrepl/zrepl/issues/505

client/status/viewmodel/render.go

@@ -216,7 +216,7 @@ func drawJob(t *stringbuilder.B, name string, v *job.Status, history *bytesProgr
 	}
 }
 
-func printFilesystemStatus(t *stringbuilder.B, rep *report.FilesystemReport, active bool, maxFS int) {
+func printFilesystemStatus(t *stringbuilder.B, rep *report.FilesystemReport, maxFS int) {
 
 	expected, replicated, containsInvalidSizeEstimates := rep.BytesSum()
 	sizeEstimationImpreciseNotice := ""
@@ -235,7 +235,8 @@ func printFilesystemStatus(t *stringbuilder.B, rep *report.FilesystemReport, act
 	)
 
 	activeIndicator := " "
-	if active {
+	if rep.BlockedOn == report.FsBlockedOnNothing &&
+		(rep.State == report.FilesystemPlanning || rep.State == report.FilesystemStepping) {
 		activeIndicator = "*"
 	}
 	t.AddIndent(1)
@@ -385,7 +386,7 @@ func renderReplicationReport(t *stringbuilder.B, rep *report.Report, history *by
 			}
 		}
 		for _, fs := range latest.Filesystems {
-			printFilesystemStatus(t, fs, false, maxFSLen) // FIXME bring 'active' flag back
+			printFilesystemStatus(t, fs, maxFSLen)
 		}
 
 	}

replication/driver/replication_driver.go

@@ -151,6 +151,8 @@ type fs struct {
 
 	l *chainlock.L
 
+	blockedOn report.FsBlockedOn
+
 	// ordering relationship that must be maintained for initial replication
 	initialRepOrd struct {
 		parents, children []*fs
@@ -158,8 +160,9 @@ type fs struct {
 	}
 
 	planning struct {
-		done bool
+		waitingForStepQueue bool
-		err  *timedError
+		done                bool
+		err                 *timedError
 	}
 
 	// valid iff planning.done && planning.err == nil
@@ -337,8 +340,9 @@ func (a *attempt) doGlobalPlanning(ctx context.Context, prev *attempt) map[*fs]*
 
 	for _, pfs := range pfss {
 		fs := &fs{
-			fs: pfs,
+			fs:        pfs,
-			l:  a.l,
+			l:         a.l,
+			blockedOn: report.FsBlockedOnNothing,
 		}
 		fs.initialRepOrd.parentDidUpdate = make(chan struct{}, 1)
 		a.fss = append(a.fss, fs)
@@ -448,6 +452,10 @@ func (a *attempt) doFilesystems(ctx context.Context, prevs map[*fs]*fs) {
 			ctx, endTask := trace.WithTaskAndSpan(ctx, "repl-fs", f.report().Info.Name)
 			defer endTask()
 			f.do(ctx, stepQueue, prevs[f])
+			f.l.HoldWhile(func() {
+				// every return from f means it's unblocked...
+				f.blockedOn = report.FsBlockedOnNothing
+			})
 		}(f)
 	}
 	a.l.DropWhile(func() {
@@ -486,11 +494,16 @@ func (f *fs) do(ctx context.Context, pq *stepQueue, prev *fs) {
 	var psteps []Step
 	var errTime time.Time
 	var err error
+	f.blockedOn = report.FsBlockedOnPlanningStepQueue
 	f.l.DropWhile(func() {
 		// TODO hacky
 		// choose target time that is earlier than any snapshot, so fs planning is always prioritized
 		targetDate := time.Unix(0, 0)
 		defer pq.WaitReady(ctx, f, targetDate)()
+		f.l.HoldWhile(func() {
+			// transition before we call PlanFS
+			f.blockedOn = report.FsBlockedOnNothing
+		})
 		psteps, err = f.fs.PlanFS(ctx) // no shadow
 		errTime = time.Now()           // no shadow
 	})
@@ -545,6 +558,7 @@ func (f *fs) do(ctx context.Context, pq *stepQueue, prev *fs) {
 	f.planning.done = true
 
 	// wait for parents' initial replication
+	f.blockedOn = report.FsBlockedOnParentInitialRepl
 	var parents []string
 	for _, p := range f.initialRepOrd.parents {
 		parents = append(parents, p.fs.ReportInfo().Name)
@@ -613,7 +627,6 @@ func (f *fs) do(ctx context.Context, pq *stepQueue, prev *fs) {
 			select {
 			case <-ctx.Done():
 				f.planned.stepErr = newTimedError(ctx.Err(), time.Now())
-				return
 			case <-f.initialRepOrd.parentDidUpdate:
 				// loop
 			}
@@ -631,7 +644,9 @@ func (f *fs) do(ctx context.Context, pq *stepQueue, prev *fs) {
 		f.l.DropWhile(func() {
 			// wait for parallel replication
 			targetDate := s.step.TargetDate()
+			f.l.HoldWhile(func() { f.blockedOn = report.FsBlockedOnReplStepQueue })
 			defer pq.WaitReady(ctx, f, targetDate)()
+			f.l.HoldWhile(func() { f.blockedOn = report.FsBlockedOnNothing })
 			// do the step
 			ctx, endSpan := trace.WithSpan(ctx, fmt.Sprintf("%#v", s.step.ReportInfo()))
 			defer endSpan()
@@ -725,6 +740,7 @@ func (f *fs) report() *report.FilesystemReport {
 	r := &report.FilesystemReport{
 		Info:        f.fs.ReportInfo(),
 		State:       state,
+		BlockedOn:   f.blockedOn,
 		PlanError:   f.planning.err.IntoReportError(),
 		StepError:   f.planned.stepErr.IntoReportError(),
 		Steps:       make([]*report.StepReport, len(f.planned.steps)),

replication/report/replication_report.go

@@ -62,11 +62,23 @@ const (
 	FilesystemDone            FilesystemState = "done"
 )
 
+type FsBlockedOn string
+
+const (
+	FsBlockedOnNothing           FsBlockedOn = "nothing"
+	FsBlockedOnPlanningStepQueue FsBlockedOn = "plan-queue"
+	FsBlockedOnParentInitialRepl FsBlockedOn = "parent-initial-repl"
+	FsBlockedOnReplStepQueue     FsBlockedOn = "repl-queue"
+)
+
 type FilesystemReport struct {
 	Info *FilesystemInfo
 
 	State FilesystemState
 
+	// Always valid.
+	BlockedOn FsBlockedOn
+
 	// Valid in State = FilesystemPlanningErrored
 	PlanError *TimedError
 	// Valid in State = FilesystemSteppingErrored