Worker: avoid task errors on shutdown

When shutting down, the main worker context closes. This causes the
subprocess to be killed, which in turn caused a task execution error. This
now no longer happens, as such errors are expected on shutdown and do not
indicate task failure.

internal/worker/listener.go

@@ -109,5 +109,12 @@ func (l *Listener) OutputProduced(ctx context.Context, taskID string, outputLoca
 }
 
 func (l *Listener) sendTaskUpdate(ctx context.Context, taskID string, update api.TaskUpdateJSONRequestBody) error {
+	// Check whether the context is closed before doing anything.
+	select {
+	default:
+	case <-ctx.Done():
+		return ctx.Err()
+	}
+
 	return l.buffer.SendTaskUpdate(ctx, taskID, update)
 }

internal/worker/state_awake.go

@@ -4,6 +4,7 @@ package worker
 
 import (
 	"context"
+	"errors"
 	"net/http"
 	"time"
 
@@ -55,10 +56,9 @@ func (w *Worker) runStateAwake(ctx context.Context) {
 		// to the Manager. This code only needs to fetch a task and run it.
 		err := w.taskRunner.Run(ctx, *task)
 		if err != nil {
-			select {
+			if errors.Is(err, context.Canceled) {
-			case <-ctx.Done():
+				log.Warn().Interface("task", *task).Msg("task aborted due to context being closed")
-				log.Warn().Err(err).Interface("task", *task).Msg("task aborted due to context being closed")
+			} else {
-			default:
 				log.Warn().Err(err).Interface("task", *task).Msg("error executing task")
 			}
 		}
@@ -72,7 +72,6 @@ func (w *Worker) runStateAwake(ctx context.Context) {
 // Returns nil when a task could not be obtained and the period loop was cancelled.
 func (w *Worker) fetchTask(ctx context.Context) *api.AssignedTask {
 	logger := log.With().Str("status", string(w.state)).Logger()
-	logger.Info().Msg("fetching tasks")
 
 	// Initially don't wait at all.
 	var wait time.Duration
@@ -88,6 +87,7 @@ func (w *Worker) fetchTask(ctx context.Context) *api.AssignedTask {
 		case <-time.After(wait):
 		}
 
+		logger.Info().Msg("fetching tasks")
 		resp, err := w.client.ScheduleTaskWithResponse(ctx)
 		if err != nil {
 			log.Error().Err(err).Msg("error obtaining task")

internal/worker/task_executor.go

@@ -4,6 +4,7 @@ package worker
 
 import (
 	"context"
+	"errors"
 	"fmt"
 
 	"github.com/rs/zerolog/log"
@@ -72,6 +73,10 @@ func (te *TaskExecutor) Run(ctx context.Context, task api.AssignedTask) error {
 			// All was fine, go run the next command.
 			continue
 		}
+		if errors.Is(runErr, context.Canceled) {
+			logger.Warn().Msg("task execution aborted due to context shutdown")
+			return nil
+		}
 
 		// Notify Manager that this task failed.
 		if err := te.listener.TaskFailed(ctx, task.Uuid, runErr.Error()); err != nil {