Logs: set ObservedTimestamp field (#3565)

* Logs: set ObservedTimestamp field

* Update CHANGELOG.md

---------

CHANGELOG.md

@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+- Logs: set `observed_timestamp` field
+  ([#3565](https://github.com/open-telemetry/opentelemetry-python/pull/3565))
 - Add missing Resource SchemaURL in OTLP exporters
   ([#3652](https://github.com/open-telemetry/opentelemetry-python/pull/3652))
 - Fix loglevel warning text

opentelemetry-sdk/src/opentelemetry/sdk/_logs/_internal/__init__.py

@@ -477,6 +477,7 @@ def _get_attributes(record: logging.LogRecord) -> Attributes:
 
     def _translate(self, record: logging.LogRecord) -> LogRecord:
         timestamp = int(record.created * 1e9)
+        observered_timestamp = time_ns()
         span_context = get_current_span().get_span_context()
         attributes = self._get_attributes(record)
         # This comment is taken from GanyedeNil's PR #3343, I have redacted it
@@ -530,6 +531,7 @@ def _translate(self, record: logging.LogRecord) -> LogRecord:
 
         return LogRecord(
             timestamp=timestamp,
+            observed_timestamp=observered_timestamp,
             trace_id=span_context.trace_id,
             span_id=span_context.span_id,
             trace_flags=span_context.trace_flags,

opentelemetry-sdk/tests/logs/test_handler.py

@@ -98,6 +98,20 @@ def test_log_record_no_span_context(self):
             log_record.trace_flags, INVALID_SPAN_CONTEXT.trace_flags
         )
 
+    def test_log_record_observed_timestamp(self):
+        emitter_provider_mock = Mock(spec=LoggerProvider)
+        emitter_mock = APIGetLogger(
+            __name__, logger_provider=emitter_provider_mock
+        )
+        logger = get_logger(logger_provider=emitter_provider_mock)
+        # Assert emit gets called for warning message
+        with self.assertLogs(level=logging.WARNING):
+            logger.warning("Warning message")
+        args, _ = emitter_mock.emit.call_args_list[0]
+        log_record = args[0]
+
+        self.assertIsNotNone(log_record.observed_timestamp)
+
     def test_log_record_user_attributes(self):
         """Attributes can be injected into logs by adding them to the LogRecord"""
         emitter_provider_mock = Mock(spec=LoggerProvider)