[SVLS-4422] Support for metrics with timestamps when the Extension is present (DataDog#480)

use API to send metrics with timestamps when extension is present

Author: DylanLovesCoffee

datadog_lambda/api.py

@@ -1,7 +1,6 @@
 import os
 import logging
 import base64
-from datadog_lambda.extension import should_use_extension
 
 logger = logging.getLogger(__name__)
 KMS_ENCRYPTION_CONTEXT_KEY = "LambdaFunctionName"
@@ -48,13 +47,10 @@ def decrypt_kms_api_key(kms_client, ciphertext):
 
 
 def init_api():
-    if (
-        not should_use_extension
-        and not os.environ.get("DD_FLUSH_TO_LOG", "").lower() == "true"
-    ):
+    if not os.environ.get("DD_FLUSH_TO_LOG", "").lower() == "true":
         # Make sure that this package would always be lazy-loaded/outside from the critical path
         # since underlying packages are quite heavy to load
-        # and useless when the extension is present
+        # and useless with the extension unless sending metrics with timestamps
         from datadog import api
 
         if not api._api_key:

datadog_lambda/metric.py

@@ -10,13 +10,13 @@
 
 from datadog_lambda.extension import should_use_extension
 from datadog_lambda.tags import get_enhanced_metrics_tags, dd_lambda_layer_tag
-from datadog_lambda.api import init_api
 
 logger = logging.getLogger(__name__)
 
 lambda_stats = None
+extension_thread_stats = None
 
-init_api()
+flush_in_thread = os.environ.get("DD_FLUSH_IN_THREAD", "").lower() == "true"
 
 if should_use_extension:
     from datadog_lambda.statsd_writer import StatsDWriter
@@ -28,8 +28,9 @@
     # end of invocation. To make metrics submitted from a long-running Lambda
     # function available sooner, consider using the Datadog Lambda extension.
     from datadog_lambda.thread_stats_writer import ThreadStatsWriter
+    from datadog_lambda.api import init_api
 
-    flush_in_thread = os.environ.get("DD_FLUSH_IN_THREAD", "").lower() == "true"
+    init_api()
     lambda_stats = ThreadStatsWriter(flush_in_thread)
 
 enhanced_metrics_enabled = (
@@ -57,6 +58,22 @@ def lambda_metric(metric_name, value, timestamp=None, tags=None, force_async=Fal
     tags = [] if tags is None else list(tags)
     tags.append(dd_lambda_layer_tag)
 
+    if should_use_extension and timestamp is not None:
+        # The extension does not support timestamps for distributions so we create a
+        # a thread stats writer to submit metrics with timestamps to the API
+        global extension_thread_stats
+        if extension_thread_stats is None:
+            from datadog_lambda.thread_stats_writer import ThreadStatsWriter
+            from datadog_lambda.api import init_api
+
+            init_api()
+            extension_thread_stats = ThreadStatsWriter(flush_in_thread)
+
+        extension_thread_stats.distribution(
+            metric_name, value, tags=tags, timestamp=timestamp
+        )
+        return
+
     if should_use_extension:
         logger.debug(
             "Sending metric %s value %s to Datadog via extension", metric_name, value
@@ -94,6 +111,9 @@ def write_metric_point_to_stdout(metric_name, value, timestamp=None, tags=[]):
 def flush_stats():
     lambda_stats.flush()
 
+    if extension_thread_stats is not None:
+        extension_thread_stats.flush()
+
 
 def submit_enhanced_metric(metric_name, lambda_context):
     """Submits the enhanced metric with the given name

tests/test_metric.py

@@ -43,6 +43,18 @@ def test_lambda_metric_flush_to_log_with_extension(self):
         )
         del os.environ["DD_FLUSH_TO_LOG"]
 
+    @patch("datadog_lambda.metric.should_use_extension", True)
+    def test_lambda_metric_timestamp_with_extension(self):
+        patcher = patch("datadog_lambda.metric.extension_thread_stats")
+        self.mock_metric_extension_thread_stats = patcher.start()
+        self.addCleanup(patcher.stop)
+
+        lambda_metric("test_timestamp", 1, 123)
+        self.mock_metric_lambda_stats.distribution.assert_not_called()
+        self.mock_metric_extension_thread_stats.distribution.assert_called_with(
+            "test_timestamp", 1, timestamp=123, tags=[dd_lambda_layer_tag]
+        )
+
     def test_lambda_metric_flush_to_log(self):
         os.environ["DD_FLUSH_TO_LOG"] = "True"