progressui: print logs for failed step as summary in plain mode

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

util/progress/progressui/display.go

@@ -2,6 +2,7 @@ package progressui
 
 import (
 	"bytes"
+	"container/ring"
 	"context"
 	"fmt"
 	"io"
@@ -130,6 +131,7 @@ type vertex struct {
 	logs          [][]byte
 	logsPartial   bool
 	logsOffset    int
+	logsBuffer    *ring.Ring // stores last logs to print them on error
 	prev          *client.Vertex
 	events        []string
 	lastBlockTime *time.Time
@@ -295,10 +297,20 @@ func (t *trace) printErrorLogs(f io.Writer) {
 		if v.Error != "" && !strings.HasSuffix(v.Error, context.Canceled.Error()) {
 			fmt.Fprintln(f, "------")
 			fmt.Fprintf(f, " > %s:\n", v.Name)
+			// tty keeps original logs
 			for _, l := range v.logs {
 				f.Write(l)
 				fmt.Fprintln(f)
 			}
+			// printer keeps last logs buffer
+			if v.logsBuffer != nil {
+				for i := 0; i < v.logsBuffer.Len(); i++ {
+					if v.logsBuffer.Value != nil {
+						fmt.Fprintln(f, string(v.logsBuffer.Value.([]byte)))
+					}
+					v.logsBuffer = v.logsBuffer.Next()
+				}
+			}
 			fmt.Fprintln(f, "------")
 		}
 	}

util/progress/progressui/printer.go

@@ -1,6 +1,7 @@
 package progressui
 
 import (
+	"container/ring"
 	"context"
 	"fmt"
 	"io"
@@ -18,6 +19,8 @@ const maxDelay = 10 * time.Second
 const minTimeDelta = 5 * time.Second
 const minProgressDelta = 0.05 // %
 
+const logsBufferSize = 10
+
 type lastStatus struct {
 	Current   int64
 	Timestamp time.Time
@@ -130,6 +133,13 @@ func (p *textMux) printVtx(t *trace, dgst digest.Digest) {
 		if i != len(v.logs)-1 || !v.logsPartial {
 			fmt.Fprintln(p.w, "")
 		}
+		if v.logsBuffer == nil {
+			v.logsBuffer = ring.New(logsBufferSize)
+		}
+		v.logsBuffer.Value = l
+		if !v.logsPartial {
+			v.logsBuffer = v.logsBuffer.Next()
+		}
 	}
 
 	if len(v.logs) > 0 {