Merge branch 'master' into aj-v4.0.1-prep

* master:
  remove unused import
  improve logging around buildsh-trace

backend/backend.go

@@ -1,6 +1,7 @@
 package backend
 
 import (
+	"errors"
 	"fmt"
 	"sort"
 	"sync"
@@ -13,6 +14,8 @@ var (
 	backendRegistryMutex sync.Mutex
 )
 
+var ErrDownloadTraceNotImplemented = errors.New("DownloadTrace not implemented")
+
 // Backend wraps up an alias, backend provider help, and a factory func for a
 // given backend provider wheee
 type Backend struct {

backend/cloudbrain.go

@@ -585,7 +585,7 @@ func (i *cbInstance) RunScript(ctx gocontext.Context, output io.Writer) (*RunRes
 }
 
 func (i *cbInstance) DownloadTrace(ctx gocontext.Context) ([]byte, error) {
-	return nil, errors.New("DownloadTrace not implemented")
+	return nil, ErrDownloadTraceNotImplemented
 }
 
 func (i *cbInstance) Stop(ctx gocontext.Context) error {

backend/docker.go

@@ -729,7 +729,7 @@ func (i *dockerInstance) runScriptSSH(ctx gocontext.Context, output io.Writer) (
 }
 
 func (i *dockerInstance) DownloadTrace(ctx gocontext.Context) ([]byte, error) {
-	return nil, errors.New("DownloadTrace not implemented")
+	return nil, ErrDownloadTraceNotImplemented
 }
 
 func (i *dockerInstance) Stop(ctx gocontext.Context) error {

backend/fake.go

@@ -2,7 +2,6 @@ package backend
 
 import (
 	"context"
-	"errors"
 	"io"
 	"time"
 
@@ -82,7 +81,7 @@ func (i *fakeInstance) RunScript(ctx context.Context, writer io.Writer) (*RunRes
 }
 
 func (i *fakeInstance) DownloadTrace(ctx context.Context) ([]byte, error) {
-	return nil, errors.New("DownloadTrace not implemented")
+	return nil, ErrDownloadTraceNotImplemented
 }
 
 func (i *fakeInstance) Stop(ctx context.Context) error {

backend/jupiterbrain.go

@@ -448,7 +448,7 @@ func (i *jupiterBrainInstance) RunScript(ctx gocontext.Context, output io.Writer
 }
 
 func (i *jupiterBrainInstance) DownloadTrace(ctx gocontext.Context) ([]byte, error) {
-	return nil, errors.New("DownloadTrace not implemented")
+	return nil, ErrDownloadTraceNotImplemented
 }
 
 func (i *jupiterBrainInstance) Stop(ctx gocontext.Context) error {

backend/local.go

@@ -2,7 +2,6 @@ package backend
 
 import (
 	"bytes"
-	"errors"
 	"fmt"
 	"io"
 	"os"
@@ -124,7 +123,7 @@ func (i *localInstance) RunScript(ctx gocontext.Context, writer io.Writer) (*Run
 }
 
 func (i *localInstance) DownloadTrace(ctx gocontext.Context) ([]byte, error) {
-	return nil, errors.New("DownloadTrace not implemented")
+	return nil, ErrDownloadTraceNotImplemented
 }
 
 func (i *localInstance) Stop(ctx gocontext.Context) error {

backend/openstack.go

@@ -638,7 +638,7 @@ func (i *osInstance) RunScript(ctx gocontext.Context, output io.Writer) (*RunRes
 }
 
 func (i *osInstance) DownloadTrace(ctx gocontext.Context) ([]byte, error) {
-	return nil, errors.New("DownloadTrace not implemented")
+	return nil, ErrDownloadTraceNotImplemented
 }
 
 func (i *osInstance) Stop(ctx gocontext.Context) error {

ssh/package.go

@@ -148,7 +148,7 @@ func (c *sshConnection) DownloadFile(path string) ([]byte, error) {
 
 	_, err = sftp.Lstat(path)
 	if err != nil {
-		return nil, errors.Wrap(err, "couldn't stat file (it may be missing)")
+		return nil, errors.Wrap(err, "couldn't stat file")
 	}
 
 	f, err := sftp.OpenFile(path, os.O_RDONLY)

step_download_trace.go

@@ -1,11 +1,13 @@
 package worker
 
 import (
+	"os"
 	"time"
 
 	gocontext "context"
 
 	"github.com/mitchellh/multistep"
+	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
 	"github.com/travis-ci/worker/backend"
 	"github.com/travis-ci/worker/context"
@@ -36,6 +38,14 @@ func (s *stepDownloadTrace) Run(state multistep.StateBag) multistep.StepAction {
 
 	buf, err := instance.DownloadTrace(ctx)
 	if err != nil {
+		if err == backend.ErrDownloadTraceNotImplemented || os.IsNotExist(errors.Cause(err)) {
+			logger.WithFields(logrus.Fields{
+				"err": err,
+			}).Info("skipping trace download")
+
+			return multistep.ActionContinue
+		}
+
 		metrics.Mark("worker.job.trace.download.error")
 
 		logger.WithFields(logrus.Fields{