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fix: wait for process to stop on exit #4

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Merged
nrwiersma merged 1 commit into from
Jul 22, 2026
Merged

fix: wait for process to stop on exit #4

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13 changes: 9 additions & 4 deletions cmd/supervisor/main.go
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Original file line number Diff line number Diff line change
Expand Up @@ -73,10 +73,12 @@ func realMain() (code int) {
apiSrv := api.NewServer(*addr, super, sys, *glassBin, *dataDir, log)
webSrv := web.NewServer()

if err = super.Start(ctx); err != nil {
_, _ = fmt.Fprintf(os.Stderr, "Could not start supervisor: %v\n", err)
return 1
}
superCh := make(chan struct{})
go func() {
defer close(superCh)

super.Run(ctx)
}()

mux := http.NewServeMux()
mux.Handle("GET /{$}", webSrv)
Expand All @@ -102,6 +104,9 @@ func realMain() (code int) {
_, _ = fmt.Fprintf(os.Stderr, "Could not run server: %v\n", err)
return 1
}

<-superCh

return 0
}

Expand Down
43 changes: 19 additions & 24 deletions proc/supervisor.go
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Original file line number Diff line number Diff line change
Expand Up @@ -68,10 +68,25 @@ func New(exe *exec.Executable, opts ...Option) *Supervisor {
return s
}

// Start begins the supervision loop in a background goroutine.
func (s *Supervisor) Start(ctx context.Context) error {
go s.loop(ctx)
return nil
// Run runs the supervision loop.
func (s *Supervisor) Run(ctx context.Context) {
for {
select {
case <-ctx.Done():
return
default:
}

if !s.waitForCondition(ctx) {
return
}

if err := s.run(ctx); err != nil && !errors.Is(err, context.Canceled) {
_, _ = s.ring.Write([]byte("Process exited with error: " + err.Error() + "\n"))
}

s.restarts.Add(1)
}
}

// Restart sends SIGTERM to the running process. The supervision loop restarts it.
Expand Down Expand Up @@ -109,26 +124,6 @@ func (s *Supervisor) Follow(ctx context.Context) <-chan string {
return s.ring.Stream(ctx)
}

func (s *Supervisor) loop(ctx context.Context) {
for {
select {
case <-ctx.Done():
return
default:
}

if !s.waitForCondition(ctx) {
return
}

if err := s.run(ctx); err != nil && !errors.Is(err, context.Canceled) {
_, _ = s.ring.Write([]byte("Process exited with error: " + err.Error() + "\n"))
}

s.restarts.Add(1)
}
}

func (s *Supervisor) waitForCondition(ctx context.Context) bool {
if s.cond == nil {
return true
Expand Down
18 changes: 9 additions & 9 deletions proc/supervisor_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -35,7 +35,7 @@ func TestSupervisor_Info(t *testing.T) {
ctx, cancel := context.WithCancel(t.Context())
t.Cleanup(cancel)

require.NoError(t, sup.Start(ctx))
go sup.Run(ctx)

require.Eventually(t, func() bool {
return sup.Info().PID > 0
Expand All @@ -56,7 +56,7 @@ func TestSupervisor_Lines(t *testing.T) {
ctx, cancel := context.WithCancel(t.Context())
t.Cleanup(cancel)

require.NoError(t, sup.Start(ctx))
go sup.Run(ctx)

require.Eventually(t, func() bool {
lines := sup.Lines()
Expand All @@ -73,7 +73,7 @@ func TestSupervisor_Follow(t *testing.T) {
exe := exectest.New(t, "echo", "streamed line")
sup := proc.New(exe)

require.NoError(t, sup.Start(t.Context()))
go sup.Run(t.Context())

ch := sup.Follow(t.Context())

Expand Down Expand Up @@ -107,7 +107,7 @@ func TestSupervisor_Restart(t *testing.T) {
ctx, cancel := context.WithCancel(t.Context())
t.Cleanup(cancel)

require.NoError(t, sup.Start(ctx))
go sup.Run(ctx)

require.Eventually(t, func() bool {
return sup.Info().PID > 0
Expand All @@ -132,7 +132,7 @@ func TestSupervisor_RestartIncrementsCount(t *testing.T) {
ctx, cancel := context.WithCancel(t.Context())
t.Cleanup(cancel)

require.NoError(t, sup.Start(ctx))
go sup.Run(ctx)

require.Eventually(t, func() bool {
return sup.Info().Restarts > 0
Expand All @@ -149,7 +149,7 @@ func TestSupervisor_ConditionHoldsProcess(t *testing.T) {
ctx, cancel := context.WithCancel(t.Context())
t.Cleanup(cancel)

require.NoError(t, sup.Start(ctx))
go sup.Run(ctx)

// Give the supervisor time to attempt a start; the process must not start.
time.Sleep(100 * time.Millisecond)
Expand All @@ -167,7 +167,7 @@ func TestSupervisor_ConditionWritesReasonToBuffer(t *testing.T) {
ctx, cancel := context.WithCancel(t.Context())
t.Cleanup(cancel)

require.NoError(t, sup.Start(ctx))
go sup.Run(ctx)

require.Eventually(t, func() bool {
for _, line := range sup.Lines() {
Expand Down Expand Up @@ -198,7 +198,7 @@ func TestSupervisor_StartsWhenConditionPasses(t *testing.T) {
ctx, cancel := context.WithCancel(t.Context())
t.Cleanup(cancel)

require.NoError(t, sup.Start(ctx))
go sup.Run(ctx)

time.Sleep(100 * time.Millisecond)
assert.Equal(t, 0, sup.Info().PID, "process should not have started yet")
Expand All @@ -218,7 +218,7 @@ func TestSupervisor_StopsOnContextCancel(t *testing.T) {

ctx, cancel := context.WithCancel(t.Context())

require.NoError(t, sup.Start(ctx))
go sup.Run(ctx)

require.Eventually(t, func() bool {
return sup.Info().PID > 0
Expand Down
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