Support export OTel metrics to be EMF in starndard output

aws-opentelemetry-distro/src/amazon/opentelemetry/distro/aws_opentelemetry_configurator.py

@@ -122,7 +122,14 @@ class OtlpLogHeaderSetting(NamedTuple):
     log_group: Optional[str]
     log_stream: Optional[str]
     namespace: Optional[str]
-    is_valid: bool
+
+    def is_valid(self) -> bool:
+        """Check if the log header setting is valid by ensuring both log_group and log_stream are present."""
+        return self.log_group is not None and self.log_stream is not None
+
+
+# Singleton cache for OtlpLogHeaderSetting
+_otlp_log_header_setting_cache: Optional[OtlpLogHeaderSetting] = None
 
 
 class AwsOpenTelemetryConfigurator(_OTelSDKConfigurator):
@@ -440,7 +447,7 @@ def _customize_logs_exporter(log_exporter: LogExporter) -> LogExporter:
 
         if isinstance(log_exporter, OTLPLogExporter):
 
-            if _validate_and_fetch_logs_header().is_valid:
+            if _fetch_logs_header().is_valid():
                 endpoint, region = _extract_endpoint_and_region_from_otlp_endpoint(logs_endpoint)
                 # Setting default compression mode to Gzip as this is the behavior in upstream's
                 # collector otlp http exporter:
@@ -627,18 +634,23 @@ def _extract_endpoint_and_region_from_otlp_endpoint(endpoint: str):
     return endpoint, region
 
 
-def _validate_and_fetch_logs_header() -> OtlpLogHeaderSetting:
-    """Checks if x-aws-log-group and x-aws-log-stream are present in the headers in order to send logs to
-    AWS OTLP Logs endpoint."""
+def _fetch_logs_header() -> OtlpLogHeaderSetting:
+    """Returns the OTLP log header setting as a singleton instance."""
+    global _otlp_log_header_setting_cache  # pylint: disable=global-statement
+
+    if _otlp_log_header_setting_cache is not None:
+        return _otlp_log_header_setting_cache
 
     logs_headers = os.environ.get(OTEL_EXPORTER_OTLP_LOGS_HEADERS)
 
     if not logs_headers:
-        _logger.warning(
-            "Improper configuration: Please configure the environment variable OTEL_EXPORTER_OTLP_LOGS_HEADERS "
-            "to include x-aws-log-group and x-aws-log-stream"
-        )
-        return OtlpLogHeaderSetting(None, None, None, False)
+        if not _is_lambda_environment():
+            _logger.warning(
+                "Improper configuration: Please configure the environment variable OTEL_EXPORTER_OTLP_LOGS_HEADERS "
+                "to include x-aws-log-group and x-aws-log-stream"
+            )
+        _otlp_log_header_setting_cache = OtlpLogHeaderSetting(None, None, None)
+        return _otlp_log_header_setting_cache
 
     log_group = None
     log_stream = None
@@ -656,9 +668,14 @@ def _validate_and_fetch_logs_header() -> OtlpLogHeaderSetting:
             elif key == AWS_EMF_METRICS_NAMESPACE and value:
                 namespace = value
 
-    is_valid = log_group is not None and log_stream is not None
+    _otlp_log_header_setting_cache = OtlpLogHeaderSetting(log_group, log_stream, namespace)
+    return _otlp_log_header_setting_cache
+
 
-    return OtlpLogHeaderSetting(log_group, log_stream, namespace, is_valid)
+def _clear_logs_header_cache():
+    """Clear the singleton cache for OtlpLogHeaderSetting. Used primarily for testing."""
+    global _otlp_log_header_setting_cache  # pylint: disable=global-statement
+    _otlp_log_header_setting_cache = None
 
 
 def _get_metric_export_interval():
@@ -773,8 +790,25 @@ def _check_emf_exporter_enabled() -> bool:
 
 
 def _create_emf_exporter():
-    """Create and configure the CloudWatch EMF exporter."""
+    """
+    Create the appropriate EMF exporter based on the environment and configuration.
+
+    Returns:
+        ConsoleEmfExporter for Lambda without log headers log group and stream
+        AwsCloudWatchEmfExporter for other cases (when conditions are met)
+        None if CloudWatch exporter cannot be created
+    """
     try:
+        log_header_setting = _fetch_logs_header()
+
+        # Lambda without valid logs http headers - use Console EMF exporter
+        if _is_lambda_environment() and not log_header_setting.is_valid():
+            # pylint: disable=import-outside-toplevel
+            from amazon.opentelemetry.distro.exporter.aws.metrics.console_emf_exporter import ConsoleEmfExporter
+
+            return ConsoleEmfExporter(namespace=log_header_setting.namespace)
+
+        # For non-Lambda environment or Lambda with valid headers - use CloudWatch EMF exporter
         session = get_aws_session()
         # Check if botocore is available before importing the EMF exporter
         if not session:
@@ -786,9 +820,7 @@ def _create_emf_exporter():
             AwsCloudWatchEmfExporter,
         )
 
-        log_header_setting = _validate_and_fetch_logs_header()
-
-        if not log_header_setting.is_valid:
+        if not log_header_setting.is_valid():
             return None
 
         return AwsCloudWatchEmfExporter(