cli,log: allow use of debug merge-logs on older logs

Fixes cockroachdb#68278.

Log parsers require the flag --format when parsing older logs (because
they do not contain format specification). With this patch, this is no longer
a requirement as the log format is now inferred based on the structure of
the log if no log format specification exists.

Release justification: bug fix

Release note (bug fix): The debug merge-logs command no longer returns an
error when the log decoder attempts to parse older logs.

pkg/cli/debug_merge_logs.go

@@ -502,6 +502,14 @@ func (s *fileLogStream) open() bool {
 	if s.f, s.err = os.Open(s.fi.path); s.err != nil {
 		return false
 	}
+	if s.format == "" {
+		if _, s.format, s.err = log.ReadFormatFromLogFile(s.f); s.err != nil {
+			return false
+		}
+		if _, s.err = s.f.Seek(0, io.SeekStart); s.err != nil {
+			return false
+		}
+	}
 	if s.err = seekToFirstAfterFrom(s.f, s.from, s.editMode, s.format); s.err != nil {
 		return false
 	}

pkg/util/log/BUILD.bazel

@@ -136,6 +136,7 @@ go_test(
         "helpers_test.go",
         "http_sink_test.go",
         "intercept_test.go",
+        "log_decoder_test.go",
         "main_test.go",
         "redact_test.go",
         "secondary_log_test.go",

pkg/util/log/log_decoder.go

@@ -35,34 +35,23 @@ func NewEntryDecoder(in io.Reader, editMode EditSensitiveData) (EntryDecoder, er
 // NewEntryDecoderWithFormat is like NewEntryDecoder but the caller can specify the format of the log file.
 // The header lines do not need to be searched for the log entry format when 'logFormat' is non-empty.
 func NewEntryDecoderWithFormat(
-	in io.Reader, editMode EditSensitiveData, logFormat string,
+	in io.Reader, editMode EditSensitiveData, format string,
 ) (EntryDecoder, error) {
 	var d EntryDecoder
-	var format string
 
 	// If the log format has not been specified, get the format from the first few header lines of the log file.
-	if logFormat == "" {
-		var buf bytes.Buffer
-		rest := bufio.NewReader(in)
-		r := io.TeeReader(rest, &buf)
-		{
-			const headerBytes = 8096
-			header := make([]byte, headerBytes)
-			n, err := r.Read(header)
-			if err != nil {
-				return nil, err
-			}
-			header = header[:n]
-			logFormat, err = getLogFormat(header)
-			if err != nil {
-				return nil, errors.Wrap(err, "decoding format")
-			}
+	if format == "" {
+		var read io.Reader
+		var err error
+		read, format, err = ReadFormatFromLogFile(in)
+		if err != nil {
+			return nil, err
 		}
-		in = io.MultiReader(&buf, rest)
+		in = io.MultiReader(read, in)
 	}
-	f, ok := formatParsers[logFormat]
+	f, ok := formatParsers[format]
 	if !ok {
-		return nil, errors.Newf("unknown log file format: %s", logFormat)
+		return nil, errors.Newf("unknown log file format: %s", format)
 	}
 	format = f
 
@@ -92,18 +81,57 @@ func NewEntryDecoderWithFormat(
 	return d, nil
 }
 
+// ReadFormatFromLogFile attempts to read the format from the header data of
+// in. It returns the data consumed from input in the read return value.
+func ReadFormatFromLogFile(in io.Reader) (read io.Reader, format string, err error) {
+	var buf bytes.Buffer
+	rest := bufio.NewReader(in)
+	r := io.TeeReader(rest, &buf)
+	const headerBytes = 8096
+	header := make([]byte, headerBytes)
+	n, err := r.Read(header)
+	if err != nil {
+		return nil, "", err
+	}
+	header = header[:n]
+	format, err = getLogFormat(header)
+	if err != nil {
+		return nil, "", errors.Wrap(err, "decoding format")
+	}
+	return &buf, format, nil
+}
+
 // getLogFormat retrieves the log format recorded at the top of a log.
 func getLogFormat(data []byte) (string, error) {
 	var re = regexp.MustCompile(
 		`(?m)^` +
-			/* Prefix */ `(?:.*\[config\]   log format \(utf8=.+\): )` +
+			/* Prefix */ `(?:.*\[config\][ ]+log format \(utf8=.+\): )` +
 			/* Format */ `(.*)$`,
 	)
+	if m := re.FindSubmatch(data); m != nil {
+		return string(m[1]), nil
+	}
 
-	m := re.FindSubmatch(data)
-	if m == nil {
-		return "", errors.New("failed to extract log file format from the log")
+	// If the log format is not specified in the log, determine the format from the log structure.
+
+	// If the absence of a counter in an entry is not represented by two ASCII spaces, the format must be crdb-v1.
+	// If detected, determine that the log is crdb-v1 formatted.
+	if re = regexp.MustCompile(
+		`(?m)^` +
+			/* crdb-v1 Indicator */ `(?:.*\[config\] [a-zA-Z].*)$`,
+	); re.Match(data) {
+		return "crdb-v1", nil
+	}
+
+	// If the absence of a counter in an entry is represented by two ASCII spaces and there is a continuation marker,
+	// the format must be crdb-v2.
+	// If detected, determine that the log is crdb-v2 formatted.
+	if re = regexp.MustCompile(
+		`(?m)^` +
+			/* crdb-v2 Indicator */ `(?:.*\[config\]   [a-zA-Z].*)$`,
+	); re.Match(data) {
+		return "crdb-v2", nil
 	}
 
-	return string(m[1]), nil
+	return "", errors.New("failed to extract log file format from the log")
 }

pkg/util/log/log_decoder_test.go

@@ -0,0 +1,36 @@
+// Copyright 2021 The Cockroach Authors.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+package log
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/cockroachdb/datadriven"
+)
+
+func TestReadLogFormat(t *testing.T) {
+	datadriven.RunTest(t, "testdata/read_header",
+		func(t *testing.T, td *datadriven.TestData) string {
+			switch td.Cmd {
+			case "log":
+				_, format, err := ReadFormatFromLogFile(strings.NewReader(td.Input))
+				if err != nil {
+					td.Fatalf(t, "error while reading format from the log file: %v", err)
+				}
+				return format
+			default:
+				t.Fatalf("unknown directive: %q", td.Cmd)
+			}
+			// unreachable
+			return ""
+		})
+}

pkg/util/log/testdata/read_header

@@ -0,0 +1,53 @@
+subtest detect_v1_format
+
+log
+I210621 19:01:01.426193 1 util/log/sync_buffer.go:195 ⋮ [config] file created at: 2021/06/21 19:01:01
+I210621 19:01:01.426200 1 util/log/sync_buffer.go:195 ⋮ [config] running on machine:
+I210621 19:01:01.426205 1 util/log/sync_buffer.go:195 ⋮ [config] binary: CockroachDB CCL v20.2.7 (x86_64-apple-darwin14, built 2021/03/29 17:56:44, go1.13.14)
+I210621 19:01:01.426208 1 util/log/sync_buffer.go:195 ⋮ [config] arguments: ‹[cockroach start-single-node --insecure --listen-addr=localhost:26257 --http-addr=localhost:8080]›
+I210609 21:45:59.308670 1 util/log/sync_buffer.go:195 ⋮ [config] log format (utf8=✓): crdb-v1
+I210621 19:01:01.426216 1 util/log/sync_buffer.go:195 ⋮ [config] line format: [IWEF]yymmdd hh:mm:ss.uuuuuu goid file:line msg utf8=✓
+----
+crdb-v1
+
+subtest end
+
+subtest detect_v2_format
+
+log
+I210816 21:25:47.681121 1 util/log/file_sync_buffer.go:238 ⋮ [config]   file created at: 2021/08/16 21:25:47
+I210816 21:25:47.681129 1 util/log/file_sync_buffer.go:238 ⋮ [config]   running on machine:
+I210816 21:25:47.681135 1 util/log/file_sync_buffer.go:238 ⋮ [config]   binary: CockroachDB CCL v21.2.0-alpha.00000000-3306-g39d59f1fc9-dirty (x86_64-apple-darwin20.6.0, built , go1.16.6)
+I210816 21:25:47.681140 1 util/log/file_sync_buffer.go:238 ⋮ [config]   arguments: [‹./cockroach› ‹start-single-node› ‹--insecure› ‹--listen-addr=localhost:26258› ‹--http-addr=localhost:8081›]
+I210609 21:45:59.308670 1 util/log/file_sync_buffer.go:238 ⋮ [config]   log format (utf8=✓): crdb-v2
+I210816 21:25:47.681152 1 util/log/file_sync_buffer.go:238 ⋮ [config]   line format: [IWEF]yymmdd hh:mm:ss.uuuuuu goid [chan@]file:line redactionmark \[tags\] [counter] msg
+----
+crdb-v2
+
+subtest end
+
+subtest default_to_v1_format
+
+log
+I210621 19:01:01.426193 1 util/log/sync_buffer.go:195 ⋮ [config] file created at: 2021/06/21 19:01:01
+I210621 19:01:01.426200 1 util/log/sync_buffer.go:195 ⋮ [config] running on machine:
+I210621 19:01:01.426205 1 util/log/sync_buffer.go:195 ⋮ [config] binary: CockroachDB CCL v20.2.7 (x86_64-apple-darwin14, built 2021/03/29 17:56:44, go1.13.14)
+I210621 19:01:01.426208 1 util/log/sync_buffer.go:195 ⋮ [config] arguments: ‹[cockroach start-single-node --insecure --listen-addr=localhost:26257 --http-addr=localhost:8080]›
+I210621 19:01:01.426216 1 util/log/sync_buffer.go:195 ⋮ [config] line format: [IWEF]yymmdd hh:mm:ss.uuuuuu goid file:line msg utf8=✓
+----
+crdb-v1
+
+subtest end
+
+subtest default_to_v2_format
+
+log
+I210816 21:25:47.681121 1 util/log/file_sync_buffer.go:238 ⋮ [config]   file created at: 2021/08/16 21:25:47
+I210816 21:25:47.681129 1 util/log/file_sync_buffer.go:238 ⋮ [config]   running on machine:
+I210816 21:25:47.681135 1 util/log/file_sync_buffer.go:238 ⋮ [config]   binary: CockroachDB CCL v21.2.0-alpha.00000000-3306-g39d59f1fc9-dirty (x86_64-apple-darwin20.6.0, built , go1.16.6)
+I210816 21:25:47.681140 1 util/log/file_sync_buffer.go:238 ⋮ [config]   arguments: [‹./cockroach› ‹start-single-node› ‹--insecure› ‹--listen-addr=localhost:26258› ‹--http-addr=localhost:8081›]
+I210816 21:25:47.681152 1 util/log/file_sync_buffer.go:238 ⋮ [config]   line format: [IWEF]yymmdd hh:mm:ss.uuuuuu goid [chan@]file:line redactionmark \[tags\] [counter] msg
+----
+crdb-v2
+
+subtest end