feat(parsers.xpath): Add option to skip (header) bytes (#11933)

plugins/parsers/xpath/README.md

@@ -73,6 +73,23 @@ You should use the following setting
   ...
 ```
 
+#### `xpath_protobuf_skip_bytes` (optional)
+
+This option allows to skip a number of bytes before trying to parse
+the protocol-buffer message. This is useful in cases where the raw data
+has a header e.g. for the message length or in case of GRPC messages.
+
+This is a list of known headers and the corresponding values for
+`xpath_protobuf_skip_bytes`
+
+| name                                    | setting | comment |
+| --------------------------------------- | ------- | ------- |
+| [GRPC protocol][GRPC] | 5 | GRPC adds a 5-byte header for _Length-Prefixed-Messages_ |
+| [PowerDNS logging][PDNS] | 2 | Sent messages contain a 2-byte header containing the message length |
+
+[GRPC]: https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md
+[PDNS]: https://docs.powerdns.com/recursor/lua-config/protobuf.html
+
 ## Configuration
 
 ```toml
@@ -92,6 +109,8 @@ You should use the following setting
   # xpath_protobuf_type = "org.eclipse.tahu.protobuf.Payload"
   ## List of paths to use when looking up imported protocol-buffer definition files.
   # xpath_protobuf_import_paths = ["."]
+  ## Number of (header) bytes to ignore before parsing the message.
+  # xpath_protobuf_skip_bytes = 0
 
   ## Print the internal XML document when in debug logging mode.
   ## This is especially useful when using the parser with non-XML formats like protocol-buffers

plugins/parsers/xpath/parser.go

@@ -34,6 +34,7 @@ type Parser struct {
 	ProtobufMessageDef  string            `toml:"xpath_protobuf_file"`
 	ProtobufMessageType string            `toml:"xpath_protobuf_type"`
 	ProtobufImportPaths []string          `toml:"xpath_protobuf_import_paths"`
+	ProtobufSkipBytes   int64             `toml:"xpath_protobuf_skip_bytes"`
 	PrintDocument       bool              `toml:"xpath_print_document"`
 	AllowEmptySelection bool              `toml:"xpath_allow_empty_selection"`
 	NativeTypes         bool              `toml:"xpath_native_types"`
@@ -94,6 +95,7 @@ func (p *Parser) Init() error {
 			MessageDefinition: p.ProtobufMessageDef,
 			MessageType:       p.ProtobufMessageType,
 			ImportPaths:       p.ProtobufImportPaths,
+			SkipBytes:         p.ProtobufSkipBytes,
 			Log:               p.Log,
 		}
 		if err := pbdoc.Init(); err != nil {

plugins/parsers/xpath/parser_test.go

@@ -1,9 +1,6 @@
 package xpath
 
 import (
-	"bufio"
-	"errors"
-	"fmt"
 	"math"
 	"os"
 	"path/filepath"
@@ -11,6 +8,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/google/go-cmp/cmp"
 	"github.com/influxdata/telegraf"
 	"github.com/influxdata/telegraf/config"
 	"github.com/influxdata/telegraf/plugins/inputs"
@@ -1402,73 +1400,82 @@ func TestMultipleConfigs(t *testing.T) {
 	// Make sure the folder contains data
 	require.NotEmpty(t, folders)
 
+	// Register the wrapper plugin
+	inputs.Add("file", func() telegraf.Input {
+		return &file.File{}
+	})
+
+	// Prepare the influx parser for expectations
+	parser := &influx.Parser{}
+	require.NoError(t, parser.Init())
+
+	// Compare options
+	options := []cmp.Option{
+		testutil.IgnoreTime(),
+		testutil.SortMetrics(),
+	}
+
 	for _, f := range folders {
-		if !f.IsDir() {
+		// Only handle folders
+		if !f.IsDir() || f.Name() == "protos" {
 			continue
 		}
-		t.Run(f.Name(), func(t *testing.T) {
-			configFilename := filepath.Join("testcases", f.Name(), "telegraf.conf")
-			expectedFilename := filepath.Join("testcases", f.Name(), "expected.out")
+		testcasePath := filepath.Join("testcases", f.Name())
+		configFilename := filepath.Join(testcasePath, "telegraf.conf")
+		expectedFilename := filepath.Join(testcasePath, "expected.out")
+		expectedErrorFilename := filepath.Join(testcasePath, "expected.err")
 
-			// Process the telegraf config file for the test
-			buf, err := os.ReadFile(configFilename)
-			if err != nil && errors.Is(err, os.ErrNotExist) {
-				return
+		t.Run(f.Name(), func(t *testing.T) {
+			// Read the expected output if any
+			var expected []telegraf.Metric
+			if _, err := os.Stat(expectedFilename); err == nil {
+				var err error
+				expected, err = testutil.ParseMetricsFromFile(expectedFilename, parser)
+				require.NoError(t, err)
 			}
-			require.NoError(t, err)
-			inputs.Add("file", func() telegraf.Input {
-				return &file.File{}
-			})
+
+			// Read the expected output if any
+			var expectedErrors []string
+			if _, err := os.Stat(expectedErrorFilename); err == nil {
+				var err error
+				expectedErrors, err = testutil.ParseLinesFromFile(expectedErrorFilename)
+				require.NoError(t, err)
+				require.NotEmpty(t, expectedErrors)
+			}
+
+			// Configure the plugin
 			cfg := config.NewConfig()
-			require.NoError(t, cfg.LoadConfigData(buf))
+			require.NoError(t, cfg.LoadConfig(configFilename))
+			require.NotEmpty(t, cfg.Inputs)
 
 			// Gather the metrics from the input file configure
-			acc := testutil.Accumulator{}
+			var acc testutil.Accumulator
+			var errs []error
 			for _, input := range cfg.Inputs {
 				require.NoError(t, input.Init())
-				require.NoError(t, input.Gather(&acc))
+				err := input.Gather(&acc)
+				if err != nil {
+					errs = append(errs, err)
+				}
+			}
+
+			// Check for errors if we expect any
+			if len(expectedErrors) > 0 {
+				require.Len(t, errs, len(expectedErrors))
+				for i, err := range errs {
+					require.ErrorContains(t, err, expectedErrors[i])
+				}
+			} else {
+				require.Empty(t, errs)
 			}
 
 			// Process expected metrics and compare with resulting metrics
-			expected, err := readMetricFile(expectedFilename)
-			require.NoError(t, err)
 			actual := acc.GetTelegrafMetrics()
-			testutil.RequireMetricsEqual(t, expected, actual, testutil.IgnoreTime())
+			testutil.RequireMetricsEqual(t, expected, actual, options...)
 		})
 	}
 }
 
-func readMetricFile(filename string) ([]telegraf.Metric, error) {
-	var metrics []telegraf.Metric
-
-	f, err := os.Open(filename)
-	if err != nil {
-		return metrics, err
-	}
-	defer f.Close()
-
-	parser := &influx.Parser{}
-	if err := parser.Init(); err != nil {
-		return nil, err
-	}
-
-	scanner := bufio.NewScanner(f)
-	for scanner.Scan() {
-		line := scanner.Text()
-		if line != "" {
-			m, err := parser.ParseLine(line)
-			if err != nil {
-				return nil, fmt.Errorf("unable to parse metric in %q failed: %v", line, err)
-			}
-			// The timezone needs to be UTC to match the timestamp test results
-			m.SetTime(m.Time().UTC())
-			metrics = append(metrics, m)
-		}
-	}
-
-	return metrics, nil
-}
-
 func loadTestConfiguration(filename string) (*xpath.Config, []string, error) {
 	buf, err := os.ReadFile(filename)
 	if err != nil {

plugins/parsers/xpath/protocolbuffer_document.go

@@ -1,6 +1,7 @@
 package xpath
 
 import (
+	"encoding/hex"
 	"fmt"
 	"sort"
 	"strings"
@@ -23,6 +24,7 @@ type protobufDocument struct {
 	MessageDefinition string
 	MessageType       string
 	ImportPaths       []string
+	SkipBytes         int64
 	Log               telegraf.Logger
 	msg               *dynamicpb.Message
 }
@@ -94,7 +96,9 @@ func (d *protobufDocument) Parse(buf []byte) (dataNode, error) {
 	msg := d.msg.New()
 
 	// Unmarshal the received buffer
-	if err := proto.Unmarshal(buf, msg.Interface()); err != nil {
+	if err := proto.Unmarshal(buf[d.SkipBytes:], msg.Interface()); err != nil {
+		hexbuf := hex.EncodeToString(buf)
+		d.Log.Debugf("raw data (hex): %q (skip %d bytes)", hexbuf, d.SkipBytes)
 		return nil, err
 	}
 

plugins/parsers/xpath/testcases/protobuf_noskip_bytes_grpc/expected.err

@@ -0,0 +1 @@
+cannot parse invalid wire-format data

plugins/parsers/xpath/testcases/protobuf_noskip_bytes_grpc/message.proto

@@ -0,0 +1,10 @@
+syntax = "proto3";
+
+package native_type;
+
+message Message {
+    string a = 1;
+    double b = 2;
+    int32 c = 3;
+    bool d = 4;
+}

plugins/parsers/xpath/testcases/protobuf_noskip_bytes_grpc/telegraf.conf

@@ -0,0 +1,18 @@
+[[inputs.file]]
+  files = ["./testcases/protobuf_skip_bytes_grpc/test.dat"]
+  data_format = "xpath_protobuf"
+  xpath_native_types = true
+
+  xpath_protobuf_file = "message.proto"
+  xpath_protobuf_type = "native_type.Message"
+  xpath_protobuf_import_paths = [".", "./testcases/protobuf_skip_bytes_grpc"]
+  #xpath_protobuf_skip_bytes = 5
+
+  [[inputs.file.xpath]]
+    metric_name = "'native_types'"
+    [inputs.file.xpath.fields]
+      value_a = "//a"
+      value_b = "//b"
+      value_c = "//c"
+      value_d = "//d"
+

plugins/parsers/xpath/testcases/protobuf_skip_bytes_grpc/expected.out

@@ -0,0 +1 @@
+native_types value_a="a string",value_b=3.1415,value_c=42i,value_d=true

plugins/parsers/xpath/testcases/protobuf_skip_bytes_grpc/message.proto

@@ -0,0 +1,10 @@
+syntax = "proto3";
+
+package native_type;
+
+message Message {
+    string a = 1;
+    double b = 2;
+    int32 c = 3;
+    bool d = 4;
+}

plugins/parsers/xpath/testcases/protobuf_skip_bytes_grpc/telegraf.conf

@@ -0,0 +1,18 @@
+[[inputs.file]]
+  files = ["./testcases/protobuf_skip_bytes_grpc/test.dat"]
+  data_format = "xpath_protobuf"
+  xpath_native_types = true
+
+  xpath_protobuf_file = "message.proto"
+  xpath_protobuf_type = "native_type.Message"
+  xpath_protobuf_import_paths = [".", "./testcases/protobuf_skip_bytes_grpc"]
+  xpath_protobuf_skip_bytes = 5
+
+  [[inputs.file.xpath]]
+    metric_name = "'native_types'"
+    [inputs.file.xpath.fields]
+      value_a = "//a"
+      value_b = "//b"
+      value_c = "//c"
+      value_d = "//d"
+