[GCP encoding] Use JSON struct for all common fields and improve performance (#41467)

#### Description

This PR uses a JSON struct now instead of `map[string]any`, as we know
what to expect from a GCP log entry. This causes significant performance
improvement:

```
goos: linux
goarch: amd64
pkg: github.com/open-telemetry/opentelemetry-collector-contrib/extension/encoding/googlecloudlogentryencodingextension
cpu: 11th Gen Intel(R) Core(TM) i7-11800H @ 2.30GHz
        │   old.txt    │               new.txt               │
        │    sec/op    │   sec/op     vs base                │
Test-16   19.907µ ± 3%   6.583µ ± 4%  -66.93% (p=0.000 n=10)

        │    old.txt    │               new.txt                │
        │     B/op      │     B/op      vs base                │
Test-16   13.310Ki ± 0%   5.326Ki ± 0%  -59.98% (p=0.000 n=10)

        │   old.txt   │              new.txt               │
        │  allocs/op  │ allocs/op   vs base                │
Test-16   340.00 ± 0%   90.00 ± 0%  -73.53% (p=0.000 n=10)
```

The main goal of using a JSON struct is so that we can use semantic
conventions, like mentioned in issue
#41087.

There are also two breaking changes, since the code implemented before
was not working correctly for these cases:
- Logs also have now observedTimeUnixNano and flags
- If there is an error handling the log, just return the error and empty
logs for ALL cases. Before this behavior was inconsistent: either the
error was ignored
([here](https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/5943f5a933843e6f81bed28a05e2f33d8c1fc485/extension/encoding/googlecloudlogentryencodingextension/extension.go#L86)),
or it would stop the logs from being received
([here](https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/5943f5a933843e6f81bed28a05e2f33d8c1fc485/extension/encoding/googlecloudlogentryencodingextension/extension.go#L94))

<!-- Issue number (e.g. #1234) or full URL to issue, if applicable. -->
#### Link to tracking issue
Relates to
#41087 (comment).

<!--Describe what testing was performed and which tests were added.-->
#### Testing

Unit tests fixed.

<!--Describe the documentation added.-->
#### Documentation

N/A.

Author: constanca-m

.chloggen/gcp-add-common-fields.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: breaking
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: googlecloudlogentry_encoding
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add 'observedTimestamp' and 'flags' field to resulting log, and throw error if log failed to parse.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [41467]
+
+# (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: []

extension/encoding/googlecloudlogentryencodingextension/benchmark_test.go

@@ -0,0 +1,32 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package googlecloudlogentryencodingextension
+
+import (
+	"bytes"
+	"os"
+	"testing"
+
+	gojson "github.com/goccy/go-json"
+	"github.com/stretchr/testify/require"
+)
+
+func BenchmarkTest(b *testing.B) {
+	name := "testdata/real_log.json"
+	data, err := os.ReadFile(name)
+	require.NoError(b, err)
+
+	var dest bytes.Buffer
+	err = gojson.Compact(&dest, data)
+	require.NoError(b, err)
+
+	ex := &ext{}
+
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		_, err := ex.UnmarshalLogs(dest.Bytes())
+		require.NoError(b, err)
+	}
+}

extension/encoding/googlecloudlogentryencodingextension/extension.go

@@ -5,8 +5,9 @@ package googlecloudlogentryencodingextension // import "github.com/open-telemetr
 
 import (
 	"context"
-	stdjson "encoding/json"
+	"fmt"
 
+	gojson "github.com/goccy/go-json"
 	"go.opentelemetry.io/collector/component"
 	"go.opentelemetry.io/collector/pdata/plog"
 
@@ -16,31 +17,14 @@ import (
 var _ encoding.LogsUnmarshalerExtension = (*ext)(nil)
 
 type ext struct {
-	Config     Config
-	extractFns map[string]extractFn
+	config Config
 }
 
 func newExtension(cfg *Config) *ext {
-	return &ext{Config: *cfg}
+	return &ext{config: *cfg}
 }
 
-func (ex *ext) Start(_ context.Context, _ component.Host) error {
-	ex.extractFns = map[string]extractFn{
-		"protoPayload":     handleProtoPayload,
-		"receiveTimestamp": handleReceiveTimestamp,
-		"timestamp":        handleTimestamp,
-		"insertId":         handleInsertID,
-		"logName":          handleLogName,
-		"textPayload":      handleTextPayload,
-		"jsonPayload":      handleJSONPayload,
-		"severity":         handleSeverity,
-		"trace":            handleTrace,
-		"spanId":           handleSpanID,
-		"traceSampled":     handleTraceSampled,
-		"labels":           handleLabels,
-		"httpRequest":      handleHTTPRequest,
-		"resource":         handleResource,
-	}
+func (*ext) Start(_ context.Context, _ component.Host) error {
 	return nil
 }
 
@@ -57,40 +41,26 @@ func (ex *ext) UnmarshalLogs(buf []byte) (plog.Logs, error) {
 	return logs, nil
 }
 
-// TranslateLogEntry translates a JSON-encoded LogEntry message into a pair of
-// pcommon.Resource and plog.LogRecord, trying to keep as close as possible to
-// the semantic conventions.
+// TranslateLogEntry translates a JSON-encoded LogEntry message into plog.Logs,
+// trying to keep as close as possible to the GCP original names.
 //
 // For maximum fidelity, the decoding is done according to the protobuf message
 // schema; this ensures that a numeric value in the input is correctly
 // translated to either an integer or a double in the output. It falls back to
 // plain JSON decoding if payload type is not available in the proto registry.
 func (ex *ext) translateLogEntry(data []byte) (plog.Logs, error) {
-	var src map[string]stdjson.RawMessage
-	err := json.Unmarshal(data, &src)
-	if err != nil {
-		return plog.Logs{}, err
+	var log logEntry
+	if err := gojson.Unmarshal(data, &log); err != nil {
+		return plog.Logs{}, fmt.Errorf("failed to unmarshal log entry: %w", err)
 	}
 
 	logs := plog.NewLogs()
-	rl := logs.ResourceLogs().AppendEmpty()
-	res := rl.Resource()
-	lr := rl.ScopeLogs().AppendEmpty().LogRecords().AppendEmpty()
+	resourceLogs := logs.ResourceLogs().AppendEmpty()
+	resource := resourceLogs.Resource()
+	logRecord := resourceLogs.ScopeLogs().AppendEmpty().LogRecords().AppendEmpty()
 
-	resAttrs := res.Attributes()
-	attrs := lr.Attributes()
-
-	for key, value := range src {
-		fn := ex.extractFns[key]
-		if fn != nil {
-			kverr := fn(resAttrs, lr, attrs, key, value, ex.Config)
-			if kverr == nil {
-				delete(src, key)
-			}
-		}
+	if err := handleLogEntryFields(resource.Attributes(), logRecord, log, ex.config); err != nil {
+		return plog.Logs{}, fmt.Errorf("failed to handle log entry: %w", err)
 	}
-
-	// All other fields -> Attributes["gcp.*"]
-	err = translateInto(attrs, getLogEntryDescriptor(), src, preserveDst, prefixKeys("gcp."), snakeifyKeys)
-	return logs, err
+	return logs, nil
 }

extension/encoding/googlecloudlogentryencodingextension/extension_test.go

@@ -56,9 +56,7 @@ func TestUnmarshalLogs(t *testing.T) {
 				data := readFile(t, "testdata/real_log.json")
 				return bytes.Replace(data, []byte(`"spanId":"3e3a5741b18f0710"`), []byte(`"spanId":"13210305202245662348"`), 1)
 			}(),
-			wantFile: "testdata/invalid_span_expected.yaml",
-			setFlag:  true,
-			cfg:      *createDefaultConfig().(*Config),
+			expectsErr: "failed to handle log entry",
 		},
 	}
 

extension/encoding/googlecloudlogentryencodingextension/go.mod

@@ -3,9 +3,8 @@ module github.com/open-telemetry/opentelemetry-collector-contrib/extension/encod
 go 1.23.0
 
 require (
-	cloud.google.com/go/logging v1.13.0
+	github.com/goccy/go-json v0.10.5
 	github.com/iancoleman/strcase v0.3.0
-	github.com/json-iterator/go v1.1.12
 	github.com/open-telemetry/opentelemetry-collector-contrib/extension/encoding v0.131.0
 	github.com/open-telemetry/opentelemetry-collector-contrib/pkg/golden v0.131.0
 	github.com/open-telemetry/opentelemetry-collector-contrib/pkg/pdatatest v0.131.0
@@ -19,13 +18,11 @@ require (
 	go.opentelemetry.io/collector/pdata v1.37.0
 	go.uber.org/goleak v1.3.0
 	google.golang.org/genproto v0.0.0-20250715232539-7130f93afb79
-	google.golang.org/genproto/googleapis/api v0.0.0-20250715232539-7130f93afb79
 	google.golang.org/protobuf v1.36.6
 )
 
 require (
 	cloud.google.com/go/iam v1.5.2 // indirect
-	cloud.google.com/go/longrunning v0.6.7 // indirect
 	github.com/cespare/xxhash/v2 v2.3.0 // indirect
 	github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc // indirect
 	github.com/go-logr/logr v1.4.3 // indirect
@@ -35,6 +32,7 @@ require (
 	github.com/gogo/protobuf v1.3.2 // indirect
 	github.com/google/uuid v1.6.0 // indirect
 	github.com/hashicorp/go-version v1.7.0 // indirect
+	github.com/json-iterator/go v1.1.12 // indirect
 	github.com/knadh/koanf/maps v0.1.2 // indirect
 	github.com/knadh/koanf/providers/confmap v1.0.0 // indirect
 	github.com/knadh/koanf/v2 v2.2.2 // indirect
@@ -61,6 +59,7 @@ require (
 	golang.org/x/net v0.41.0 // indirect
 	golang.org/x/sys v0.33.0 // indirect
 	golang.org/x/text v0.26.0 // indirect
+	google.golang.org/genproto/googleapis/api v0.0.0-20250715232539-7130f93afb79 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20250707201910-8d1bb00bc6a7 // indirect
 	google.golang.org/grpc v1.74.2 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect