[exporter/syslog] Add support for octet counting in the syslog export…

…er (open-telemetry#31014)

**Description:** <Describe what has changed.>

This introduces a new configuration `enable_octet_counting` which
matches the same configuration on the syslog receiver side, and if
enabled will append the length of the message to the start of the
message.

**Link to tracking Issue:**  open-telemetry#31013

**Testing:**

Added tests alongside the existing syslog exporter tests

**Documentation:**

Updated the README with the new config option

Signed-off-by: sinkingpoint <[email protected]>

.chloggen/sinkingpoint_octet_counting.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: syslogexporter
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Adding support for sending rfc6587 octet counts in syslog messages
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [31013]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: []

exporter/syslogexporter/README.md

@@ -27,6 +27,7 @@ This means that syslog messages received via the Syslog receiver and exported vi
 - `protocol` - (default = `rfc5424`) rfc5424/rfc3164
   - `rfc5424` - Expects the syslog messages to be rfc5424 compliant
   - `rfc3164` - Expects the syslog messages to be rfc3164 compliant
+- `enable_octet_counting` (default = `false`) - Whether or not to enable rfc6587 octet counting
 - `tls` - configuration for TLS/mTLS
   - `insecure` (default = `false`) whether to enable client transport security, by default, TLS is enabled.
   - `cert_file` - Path to the TLS cert to use for TLS required connections. Should only be used if `insecure` is set to `false`.

exporter/syslogexporter/config.go

@@ -18,6 +18,7 @@ var (
 	errInvalidEndpoint     = errors.New("invalid endpoint: endpoint is required but it is not configured")
 	errUnsupportedNetwork  = errors.New("unsupported network: network is required, only tcp/udp supported")
 	errUnsupportedProtocol = errors.New("unsupported protocol: Only rfc5424 and rfc3164 supported")
+	errOctetCounting       = errors.New("octet counting is only supported for rfc5424 protocol")
 )
 
 // Config defines configuration for Syslog exporter.
@@ -33,6 +34,9 @@ type Config struct {
 	// options: rfc5424, rfc3164
 	Protocol string `mapstructure:"protocol"`
 
+	// Wether or not to enable RFC 6587 Octet Counting.
+	EnableOctetCounting bool `mapstructure:"enable_octet_counting"`
+
 	// TLSSetting struct exposes TLS client configuration.
 	TLSSetting configtls.TLSClientSetting `mapstructure:"tls"`
 
@@ -63,6 +67,10 @@ func (cfg *Config) Validate() error {
 		invalidFields = append(invalidFields, errUnsupportedProtocol)
 	}
 
+	if cfg.EnableOctetCounting && cfg.Protocol != protocolRFC5424Str {
+		invalidFields = append(invalidFields, errOctetCounting)
+	}
+
 	if len(invalidFields) > 0 {
 		return multierr.Combine(invalidFields...)
 	}

exporter/syslogexporter/exporter.go

@@ -36,7 +36,7 @@ func initExporter(cfg *Config, createSettings exporter.CreateSettings) (*sysloge
 		config:    cfg,
 		logger:    createSettings.Logger,
 		tlsConfig: tlsConfig,
-		formatter: createFormatter(cfg.Protocol),
+		formatter: createFormatter(cfg.Protocol, cfg.EnableOctetCounting),
 	}
 
 	s.logger.Info("Syslog Exporter configured",

exporter/syslogexporter/formatter.go

@@ -7,9 +7,9 @@ import (
 	"go.opentelemetry.io/collector/pdata/plog"
 )
 
-func createFormatter(protocol string) formatter {
+func createFormatter(protocol string, octetCounting bool) formatter {
 	if protocol == protocolRFC5424Str {
-		return newRFC5424Formatter()
+		return newRFC5424Formatter(octetCounting)
 	}
 	return newRFC3164Formatter()
 }

exporter/syslogexporter/rfc5424_formatter.go

@@ -13,10 +13,13 @@ import (
 )
 
 type rfc5424Formatter struct {
+	octetCounting bool
 }
 
-func newRFC5424Formatter() *rfc5424Formatter {
-	return &rfc5424Formatter{}
+func newRFC5424Formatter(octetCounting bool) *rfc5424Formatter {
+	return &rfc5424Formatter{
+		octetCounting: octetCounting,
+	}
 }
 
 func (f *rfc5424Formatter) format(logRecord plog.LogRecord) string {
@@ -30,6 +33,11 @@ func (f *rfc5424Formatter) format(logRecord plog.LogRecord) string {
 	structuredData := f.formatStructuredData(logRecord)
 	messageString := f.formatMessage(logRecord)
 	formatted := fmt.Sprintf("<%s>%s %s %s %s %s %s %s%s\n", priorityString, versionString, timestampString, hostnameString, appnameString, pidString, messageIDString, structuredData, messageString)
+
+	if f.octetCounting {
+		formatted = fmt.Sprintf("%d %s", len(formatted), formatted)
+	}
+
 	return formatted
 }
 

exporter/syslogexporter/rfc5424_formatter_test.go

@@ -29,8 +29,10 @@ func TestRFC5424Formatter(t *testing.T) {
 	require.NoError(t, err)
 	logRecord.SetTimestamp(pcommon.NewTimestampFromTime(timestamp))
 
-	actual := newRFC5424Formatter().format(logRecord)
+	actual := newRFC5424Formatter(false).format(logRecord)
 	assert.Equal(t, expected, actual)
+	octetCounting := newRFC5424Formatter(true).format(logRecord)
+	assert.Equal(t, fmt.Sprintf("%d %s", len(expected), expected), octetCounting)
 
 	expected = "<165>1 2003-10-11T22:14:15.003Z mymachine.example.com evntslog 111 ID47 - BOMAn application event log entry...\n"
 	logRecord = plog.NewLogRecord()
@@ -45,8 +47,10 @@ func TestRFC5424Formatter(t *testing.T) {
 	require.NoError(t, err)
 	logRecord.SetTimestamp(pcommon.NewTimestampFromTime(timestamp))
 
-	actual = newRFC5424Formatter().format(logRecord)
+	actual = newRFC5424Formatter(false).format(logRecord)
 	assert.Equal(t, expected, actual)
+	octetCounting = newRFC5424Formatter(true).format(logRecord)
+	assert.Equal(t, fmt.Sprintf("%d %s", len(expected), expected), octetCounting)
 
 	// Test structured data
 	expectedRegex := "\\<165\\>1 2003-08-24T12:14:15.000003Z 192\\.0\\.2\\.1 myproc 8710 - " +
@@ -72,7 +76,7 @@ func TestRFC5424Formatter(t *testing.T) {
 	require.NoError(t, err)
 	logRecord.SetTimestamp(pcommon.NewTimestampFromTime(timestamp))
 
-	actual = newRFC5424Formatter().format(logRecord)
+	actual = newRFC5424Formatter(false).format(logRecord)
 	assert.NoError(t, err)
 	matched, err := regexp.MatchString(expectedRegex, actual)
 	assert.NoError(t, err)
@@ -89,6 +93,6 @@ func TestRFC5424Formatter(t *testing.T) {
 	require.NoError(t, err)
 	logRecord.SetTimestamp(pcommon.NewTimestampFromTime(timestamp))
 
-	actual = newRFC5424Formatter().format(logRecord)
+	actual = newRFC5424Formatter(false).format(logRecord)
 	assert.Equal(t, expected, actual)
 }