OTEL-919: Add support for nested log attributes

This PR adds support for nested log attributes.

Fixes: open-telemetry/opentelemetry-collector-contrib#26382

.chloggen/mackjmr_add-support-for-nested-log-attributes.yaml

@@ -0,0 +1,16 @@
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component (e.g. pkg/quantile)
+component: pkg/otlp/logs
+
+# A brief description of the change. Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add support for nested log attributes.
+
+# The PR related to this change
+issues: [207]
+
+# (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:

pkg/otlp/logs/logs_translator.go

@@ -114,7 +114,10 @@ func Transform(lr plog.LogRecord, res pcommon.Resource, logger *zap.Logger) data
 			tagStr := strings.Join(tags, ",")
 			l.Ddtags = datadog.PtrString(tagStr)
 		default:
-			l.AdditionalProperties[k] = v.AsString()
+			m := flattenAttribute(k, v, 1)
+			for k, v := range m {
+				l.AdditionalProperties[k] = v
+			}
 		}
 		return true
 	})
@@ -172,6 +175,26 @@ func Transform(lr plog.LogRecord, res pcommon.Resource, logger *zap.Logger) data
 	return l
 }
 
+func flattenAttribute(key string, val pcommon.Value, depth int) map[string]string {
+	result := make(map[string]string)
+
+	if val.Type() != pcommon.ValueTypeMap || depth == 10 {
+		result[key] = val.AsString()
+		return result
+	}
+
+	val.Map().Range(func(k string, v pcommon.Value) bool {
+		newKey := key + "." + k
+		nestedResult := flattenAttribute(newKey, v, depth+1)
+		for nk, nv := range nestedResult {
+			result[nk] = nv
+		}
+		return true
+	})
+
+	return result
+}
+
 func extractHostNameAndServiceName(resourceAttrs pcommon.Map, logAttrs pcommon.Map) (host string, service string) {
 	if src, ok := attributes.SourceFromAttrs(resourceAttrs); ok && src.Kind == source.HostnameKind {
 		host = src.Identifier

pkg/otlp/logs/logs_translator_test.go

@@ -410,6 +410,84 @@ func TestTransform(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "Nestings",
+			args: args{
+				lr: func() plog.LogRecord {
+					l := plog.NewLogRecord()
+					sl := l.Attributes().PutEmptyMap("root")
+					sl.FromRaw(map[string]any{
+						"nest1": map[string]any{
+							"nest2": "val",
+						},
+						"nest12": map[string]any{
+							"nest22": map[string]any{
+								"nest3": "val2",
+							},
+						},
+					})
+					return l
+				}(),
+				res: func() pcommon.Resource {
+					r := pcommon.NewResource()
+					return r
+				}(),
+			},
+			want: datadogV2.HTTPLogItem{
+				Ddtags:  datadog.PtrString(""),
+				Message: *datadog.PtrString(""),
+				AdditionalProperties: map[string]string{
+					"root.nest1.nest2":         "val",
+					"root.nest12.nest22.nest3": "val2",
+					"status":                   "",
+				},
+			},
+		},
+		{
+			name: "Too many nestings",
+			args: args{
+				lr: func() plog.LogRecord {
+					l := plog.NewLogRecord()
+					sl := l.Attributes().PutEmptyMap("nest1")
+					sl.FromRaw(map[string]any{
+						"nest2": map[string]any{
+							"nest3": map[string]any{
+								"nest4": map[string]any{
+									"nest5": map[string]any{
+										"nest6": map[string]any{
+											"nest7": map[string]any{
+												"nest8": map[string]any{
+													"nest9": map[string]any{
+														"nest10": map[string]any{
+															"nest11": map[string]any{
+																"nest12": "ok",
+															},
+														},
+													},
+												},
+											},
+										},
+									},
+								},
+							},
+						},
+					})
+					return l
+				}(),
+				res: func() pcommon.Resource {
+					r := pcommon.NewResource()
+					return r
+				}(),
+			},
+			want: datadogV2.HTTPLogItem{
+				Ddtags:  datadog.PtrString(""),
+				Message: *datadog.PtrString(""),
+				AdditionalProperties: map[string]string{
+					"nest1.nest2.nest3.nest4.nest5.nest6.nest7.nest8.nest9.nest10": "{\"nest11\":{\"nest12\":\"ok\"}}",
+					"status": "",
+				},
+			},
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {