Set default test container log config to allow higher logging volume.

This is part of a series of changes to add metric charts in performance
benchmarks.

This is intended to increase the reliability of logs-based profiling metrics
by ensuring that Docker keeps enough of them around during long tests, or
tests where there are a lot of metrics being profiled, or tests with a very
fast profiling rate, or all of the above.

This also calls `sync` on the underlying logging file descriptor if possible.

Give a more helpful error messages if a log buffer overrun does occur.

PiperOrigin-RevId: 633389921

pkg/metric/profiling_metric.go

@@ -21,6 +21,7 @@ import (
 	"hash"
 	"hash/adler32"
 	"io"
+	"os"
 	"strings"
 	"time"
 
@@ -376,6 +377,10 @@ func (w *lossyBufferedWriter[T]) Flush() {
 		// have clean line endings a the time we print this.
 		w.flushBuf.WriteString("\n")
 		w.underlying.WriteString(w.flushBuf.String())
+		if f, isFile := any(w.underlying).(*os.File); isFile {
+			// If we're dealing with a file, also call `sync(2)`.
+			f.Sync()
+		}
 		w.flushBuf.Reset()
 		w.flushBuf.WriteString("\n")
 		w.lines = 0

pkg/test/dockerutil/container.go

@@ -248,6 +248,21 @@ func (c *Container) create(ctx context.Context, profileImage string, conf *conta
 		// unmodified "basic/alpine" image name. This should be easy to grok.
 		c.profileInit(profileImage)
 	}
+	if hostconf == nil || hostconf.LogConfig.Type == "" {
+		// If logging config is not explicitly specified, set it to a fairly
+		// generous default. This makes large volumes of log more reliably
+		// captured, which is useful for profiling metrics.
+		if hostconf == nil {
+			hostconf = &container.HostConfig{}
+		}
+		hostconf.LogConfig.Type = "local"
+		hostconf.LogConfig.Config = map[string]string{
+			"mode":     "blocking",
+			"max-size": "1g",
+			"max-file": "10",
+			"compress": "false",
+		}
+	}
 	cont, err := c.client.ContainerCreate(ctx, conf, hostconf, nil, nil, c.Name)
 	if err != nil {
 		return err

test/metricsviz/metricsviz.go

@@ -450,7 +450,7 @@ func Parse(logs string, hasPrefix bool) (*Data, error) {
 			}
 			wantHash := uint32(wantHashInt64)
 			if gotHash := h.Sum32(); gotHash != wantHash {
-				return nil, fmt.Errorf("hash mismatch: computed 0x%x, logs said it should be 0x%x", gotHash, wantHash)
+				return nil, fmt.Errorf("checksum mismatch: computed 0x%x, logs said it should be 0x%x. This is likely due to a log buffer overrun or similar issue causing some lines to be omitted; please configure the container or the runtime to allow higher logging volume", gotHash, wantHash)
 			}
 			checkedHash = true
 			continue
@@ -517,7 +517,7 @@ func Parse(logs string, hasPrefix bool) (*Data, error) {
 		// Regular lines.
 		tabularData := strings.Split(lineData, "\t")
 		if len(tabularData) != len(header)+1 {
-			return nil, fmt.Errorf("invalid data line: %q with %d components which does not match header %v which has %d components", line, len(tabularData), header, len(header))
+			return nil, fmt.Errorf("invalid data line: %q with %d components which does not match header which has %d components. This is likely due to a log buffer overrun or similar issue causing the line to be cut off; please configure the container or the runtime to allow higher logging volume", line, len(tabularData), len(header))
 		}
 		offsetNanos, err := strconv.ParseUint(tabularData[0], 10, 64)
 		if err != nil {