enhancement: Make context handling for log streaming more explicit

cmd/vela-worker/exec.go

@@ -94,11 +94,12 @@ func (w *Worker) exec(index int) error {
 	}
 
 	// create a background context
-	ctx := context.Background()
+	buildCtx, done := context.WithCancel(context.Background())
+	defer done()
 
 	// add to the background context with a timeout
 	// built in for ensuring a build doesn't run forever
-	ctx, timeout := context.WithTimeout(ctx, t)
+	ctx, timeout := context.WithTimeout(buildCtx, t)
 	defer timeout()
 
 	defer func() {
@@ -128,6 +129,16 @@ func (w *Worker) exec(index int) error {
 		return nil
 	}
 
+	// log streaming uses buildCtx so that it is not subject to the timeout.
+	go func() {
+		logger.Info("streaming build logs")
+		// execute the build with the executor
+		err = _executor.StreamBuild(buildCtx)
+		if err != nil {
+			logger.Errorf("unable to stream build logs: %v", err)
+		}
+	}()
+
 	logger.Info("assembling build")
 	// assemble the build with the executor
 	err = _executor.AssembleBuild(ctx)

executor/engine.go

@@ -53,6 +53,9 @@ type Engine interface {
 	// ExecBuild defines a function that
 	// runs a pipeline for a build.
 	ExecBuild(context.Context) error
+	// StreamBuild defines a function that receives a StreamRequest
+	// and then runs StreamService or StreamStep in a goroutine.
+	StreamBuild(context.Context) error
 	// DestroyBuild defines a function that
 	// cleans up the build after execution.
 	DestroyBuild(context.Context) error

executor/executor_test.go

@@ -10,6 +10,7 @@ import (
 	"testing"
 
 	"github.com/gin-gonic/gin"
+	"github.com/google/go-cmp/cmp"
 
 	"github.com/go-vela/server/mock/server"
 
@@ -77,6 +78,7 @@ func TestExecutor_New(t *testing.T) {
 		failure bool
 		setup   *Setup
 		want    Engine
+		equal   interface{}
 	}{
 		{
 			name:    "driver-darwin",
@@ -91,7 +93,8 @@ func TestExecutor_New(t *testing.T) {
 				User:     _user,
 				Version:  "v1.0.0",
 			},
-			want: nil,
+			want:  nil,
+			equal: reflect.DeepEqual,
 		},
 		{
 			name:    "driver-linux",
@@ -108,7 +111,8 @@ func TestExecutor_New(t *testing.T) {
 				User:       _user,
 				Version:    "v1.0.0",
 			},
-			want: _linux,
+			want:  _linux,
+			equal: linux.Equal,
 		},
 		{
 			name:    "driver-local",
@@ -123,7 +127,8 @@ func TestExecutor_New(t *testing.T) {
 				User:     _user,
 				Version:  "v1.0.0",
 			},
-			want: _local,
+			want:  _local,
+			equal: local.Equal,
 		},
 		{
 			name:    "driver-windows",
@@ -138,7 +143,8 @@ func TestExecutor_New(t *testing.T) {
 				User:     _user,
 				Version:  "v1.0.0",
 			},
-			want: nil,
+			want:  nil,
+			equal: reflect.DeepEqual,
 		},
 		{
 			name:    "driver-invalid",
@@ -153,7 +159,8 @@ func TestExecutor_New(t *testing.T) {
 				User:     _user,
 				Version:  "v1.0.0",
 			},
-			want: nil,
+			want:  nil,
+			equal: reflect.DeepEqual,
 		},
 		{
 			name:    "driver-empty",
@@ -168,7 +175,8 @@ func TestExecutor_New(t *testing.T) {
 				User:     _user,
 				Version:  "v1.0.0",
 			},
-			want: nil,
+			want:  nil,
+			equal: reflect.DeepEqual,
 		},
 	}
 
@@ -193,8 +201,10 @@ func TestExecutor_New(t *testing.T) {
 				t.Errorf("New returned err: %v", err)
 			}
 
-			if !reflect.DeepEqual(got, test.want) {
-				t.Errorf("New is %v, want %v", got, test.want)
+			// Comparing with reflect.DeepEqual(x, y interface) panics due to the
+			// unexported streamRequests channel.
+			if diff := cmp.Diff(test.want, got, cmp.Comparer(test.equal)); diff != "" {
+				t.Errorf("engine mismatch (-want +got):\n%v", diff)
 			}
 		})
 	}

executor/linux/build.go

@@ -491,6 +491,50 @@ func (c *client) ExecBuild(ctx context.Context) error {
 	return c.err
 }
 
+// StreamBuild receives a StreamRequest and then
+// runs StreamService or StreamStep in a goroutine.
+func (c *client) StreamBuild(ctx context.Context) error {
+	// create an error group with the parent context
+	//
+	// https://pkg.go.dev/golang.org/x/sync/errgroup?tab=doc#WithContext
+	streams, streamCtx := errgroup.WithContext(ctx)
+
+	defer func() {
+		c.Logger.Trace("waiting for stream functions to return")
+
+		err := streams.Wait()
+		if err != nil {
+			c.Logger.Errorf("error in a stream request, %v", err)
+		}
+
+		c.Logger.Info("all stream functions have returned")
+	}()
+
+	for {
+		select {
+		case req := <-c.streamRequests:
+			streams.Go(func() error {
+				// update engine logger with step metadata
+				//
+				// https://pkg.go.dev/github.com/sirupsen/logrus?tab=doc#Entry.WithField
+				logger := c.Logger.WithField(req.Key, req.Container.Name)
+
+				logger.Debugf("streaming %s container %s", req.Key, req.Container.ID)
+
+				err := req.Stream(streamCtx, req.Container)
+				if err != nil {
+					logger.Error(err)
+				}
+
+				return nil
+			})
+		case <-ctx.Done():
+			// build done or canceled
+			return nil
+		}
+	}
+}
+
 // DestroyBuild cleans up the build after execution.
 func (c *client) DestroyBuild(ctx context.Context) error {
 	var err error