feat(metrics): add runtime validations for the metric name (#7026)

* Added runtime validation for the metric name

* Updated the tests to test the EMFMetricProvider

---------

Co-authored-by: Swopnil Dangol <sdangol@amazon.co.uk>

Author: sdangol

aws_lambda_powertools/metrics/base.py

@@ -25,7 +25,13 @@
 )
 from aws_lambda_powertools.metrics.functions import convert_timestamp_to_emf_format, validate_emf_timestamp
 from aws_lambda_powertools.metrics.provider import cold_start
-from aws_lambda_powertools.metrics.provider.cloudwatch_emf.constants import MAX_DIMENSIONS, MAX_METRICS
+from aws_lambda_powertools.metrics.provider.cloudwatch_emf.constants import (
+    MAX_DIMENSIONS,
+    MAX_METRIC_NAME_LENGTH,
+    MAX_METRICS,
+    MIN_METRIC_NAME_LENGTH,
+)
+from aws_lambda_powertools.metrics.provider.cloudwatch_emf.exceptions import MetricNameError
 from aws_lambda_powertools.metrics.provider.cloudwatch_emf.metric_properties import MetricResolution, MetricUnit
 from aws_lambda_powertools.metrics.provider.cold_start import (
     reset_cold_start_flag,  # noqa: F401  # backwards compatibility
@@ -129,11 +135,18 @@ def add_metric(
 
         Raises
         ------
+        MetricNameError
+            When metric name does not fall under Cloudwatch constraints
         MetricUnitError
             When metric unit is not supported by CloudWatch
         MetricResolutionError
             When metric resolution is not supported by CloudWatch
         """
+        name = name.strip()
+        if len(name) < MIN_METRIC_NAME_LENGTH or len(name) > MAX_METRIC_NAME_LENGTH:
+            raise MetricNameError(
+                f"The metric name should be between {MIN_METRIC_NAME_LENGTH} and {MAX_METRIC_NAME_LENGTH} characters",
+            )
         if not isinstance(value, numbers.Number):
             raise MetricValueError(f"{value} is not a valid number")
 

aws_lambda_powertools/metrics/provider/cloudwatch_emf/cloudwatch.py

@@ -20,7 +20,13 @@
     validate_emf_timestamp,
 )
 from aws_lambda_powertools.metrics.provider.base import BaseProvider
-from aws_lambda_powertools.metrics.provider.cloudwatch_emf.constants import MAX_DIMENSIONS, MAX_METRICS
+from aws_lambda_powertools.metrics.provider.cloudwatch_emf.constants import (
+    MAX_DIMENSIONS,
+    MAX_METRIC_NAME_LENGTH,
+    MAX_METRICS,
+    MIN_METRIC_NAME_LENGTH,
+)
+from aws_lambda_powertools.metrics.provider.cloudwatch_emf.exceptions import MetricNameError
 from aws_lambda_powertools.metrics.provider.cloudwatch_emf.metric_properties import MetricResolution, MetricUnit
 from aws_lambda_powertools.shared import constants
 from aws_lambda_powertools.shared.functions import resolve_env_var_choice
@@ -137,6 +143,11 @@ def add_metric(
             When metric resolution is not supported by CloudWatch
         """
 
+        name = name.strip()
+        if len(name) < MIN_METRIC_NAME_LENGTH or len(name) > MAX_METRIC_NAME_LENGTH:
+            raise MetricNameError(
+                f"The metric name should be between {MIN_METRIC_NAME_LENGTH} and {MAX_METRIC_NAME_LENGTH} characters",
+            )
         if not isinstance(value, numbers.Number):
             raise MetricValueError(f"{value} is not a valid number")
 

aws_lambda_powertools/metrics/provider/cloudwatch_emf/constants.py

@@ -1,2 +1,4 @@
 MAX_DIMENSIONS = 29
 MAX_METRICS = 100
+MIN_METRIC_NAME_LENGTH = 1
+MAX_METRIC_NAME_LENGTH = 255

aws_lambda_powertools/metrics/provider/cloudwatch_emf/exceptions.py

@@ -1,3 +1,9 @@
+class MetricNameError(Exception):
+    """When metric name does not fall under Cloudwatch constraints"""
+
+    pass
+
+
 class MetricUnitError(Exception):
     """When metric unit is not supported by CloudWatch"""
 

tests/functional/metrics/required_dependencies/test_metrics_cloudwatch_emf.py

@@ -24,7 +24,10 @@
 )
 from aws_lambda_powertools.metrics.provider.cloudwatch_emf.constants import (
     MAX_DIMENSIONS,
+    MAX_METRIC_NAME_LENGTH,
+    MIN_METRIC_NAME_LENGTH,
 )
+from aws_lambda_powertools.metrics.provider.cloudwatch_emf.exceptions import MetricNameError
 
 if TYPE_CHECKING:
     from aws_lambda_powertools.metrics.provider.cloudwatch_emf.types import (
@@ -443,6 +446,38 @@ def test_schema_validation_no_namespace(metric, dimension):
             my_metric.add_dimension(**dimension)
 
 
+def test_schema_validation_empty_metric_name(metric, dimension, namespace):
+    # GIVEN we pass an empty metric name
+    my_metrics = AmazonCloudWatchEMFProvider(namespace=namespace)
+    metric["name"] = ""
+
+    # WHEN we attempt to add a metric
+    # THEN it should fail validation and raise MetricNameError
+    with pytest.raises(
+        MetricNameError,
+        match=f"The metric name should be between {MIN_METRIC_NAME_LENGTH} and {MAX_METRIC_NAME_LENGTH} characters",
+    ):
+        my_metrics.add_metric(**metric)
+
+
+def test_schema_validation_long_metric_name(metric, dimension, namespace):
+    # GIVEN we pass a metric name outside the maximum length constraint
+    my_metrics = AmazonCloudWatchEMFProvider(namespace=namespace)
+    metric[
+        "name"
+    ] = """Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Aenean commodo ligula eget dolor. Aenean massa.
+        Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Donec quam felis,
+        ultricies nec, pellentesque eu, pretium quis,."""
+
+    # WHEN we attempt to serialize a valid EMF object
+    # THEN it should fail validation and raise SchemaValidationError
+    with pytest.raises(
+        MetricNameError,
+        match=f"The metric name should be between {MIN_METRIC_NAME_LENGTH} and {MAX_METRIC_NAME_LENGTH} characters",
+    ):
+        my_metrics.add_metric(**metric)
+
+
 def test_schema_validation_incorrect_metric_value(metric, dimension, namespace):
     # GIVEN we pass an incorrect metric value (non-numeric)
     metric["value"] = "some_value"