feat: add opentelemetry utility functions and unit tests (#2570)

* add opentelemetry utility functions and unit tests

* review comments

* add label validation

tests/unit/test_telemetry.py

@@ -0,0 +1,112 @@
+import pytest
+import threading
+from langflow.services.telemetry.opentelemetry import OpenTelemetry
+from concurrent.futures import ThreadPoolExecutor, as_completed
+
+
+fixed_labels = {"flow_id": "this_flow_id", "service": "this", "user": "that"}
+
+
+@pytest.fixture
+def opentelemetry_instance():
+    return OpenTelemetry()
+
+
+def test_init(opentelemetry_instance):
+    assert isinstance(opentelemetry_instance, OpenTelemetry)
+    assert len(opentelemetry_instance._metrics) > 1
+    assert len(opentelemetry_instance._metrics) == len(opentelemetry_instance._metrics_registry) == 2
+    assert "file_uploads" in opentelemetry_instance._metrics
+
+
+def test_gauge(opentelemetry_instance):
+    opentelemetry_instance.update_gauge("file_uploads", 1024, fixed_labels)
+
+
+def test_gauge_with_counter_method(opentelemetry_instance):
+    with pytest.raises(ValueError, match="Metric 'file_uploads' is not a counter"):
+        opentelemetry_instance.increment_counter(metric_name="file_uploads", value=1, labels=fixed_labels)
+
+
+def test_gauge_with_historgram_method(opentelemetry_instance):
+    with pytest.raises(ValueError, match="Metric 'file_uploads' is not a histogram"):
+        opentelemetry_instance.observe_histogram("file_uploads", 1, fixed_labels)
+
+
+def test_gauge_with_up_down_counter_method(opentelemetry_instance):
+    with pytest.raises(ValueError, match="Metric 'file_uploads' is not an up down counter"):
+        opentelemetry_instance.up_down_counter("file_uploads", 1, labels=fixed_labels)
+
+
+def test_increment_counter(opentelemetry_instance):
+    opentelemetry_instance.increment_counter(metric_name="num_files_uploaded", value=5, labels=fixed_labels)
+
+
+def test_increment_counter_empty_label(opentelemetry_instance):
+    with pytest.raises(ValueError, match="Labels must be provided for the metric"):
+        opentelemetry_instance.increment_counter(metric_name="num_files_uploaded", value=5, labels={})
+
+
+def test_increment_counter_missing_mandatory_label(opentelemetry_instance):
+    with pytest.raises(ValueError, match="Missing required labels: {'flow_id'}"):
+        opentelemetry_instance.increment_counter(metric_name="num_files_uploaded", value=5, labels={"service": "one"})
+
+
+def test_increment_counter_unregisted_metric(opentelemetry_instance):
+    with pytest.raises(ValueError, match="Metric 'num_files_uploaded_1' is not registered"):
+        opentelemetry_instance.increment_counter(metric_name="num_files_uploaded_1", value=5, labels=fixed_labels)
+
+
+def test_opentelementry_singleton(opentelemetry_instance):
+    opentelemetry_instance_2 = OpenTelemetry()
+    assert opentelemetry_instance is opentelemetry_instance_2
+
+    opentelemetry_instance_3 = OpenTelemetry(prometheus_enabled=False)
+    assert opentelemetry_instance is opentelemetry_instance_3
+    assert opentelemetry_instance.prometheus_enabled == opentelemetry_instance_3.prometheus_enabled
+
+
+def test_missing_labels(opentelemetry_instance):
+    with pytest.raises(ValueError, match="Labels must be provided for the metric"):
+        opentelemetry_instance.increment_counter(metric_name="num_files_uploaded", labels=None, value=1.0)
+    with pytest.raises(ValueError, match="Labels must be provided for the metric"):
+        opentelemetry_instance.up_down_counter("num_files_uploaded", 1, None)
+    with pytest.raises(ValueError, match="Labels must be provided for the metric"):
+        opentelemetry_instance.update_gauge(metric_name="num_files_uploaded", value=1.0, labels=dict())
+    with pytest.raises(ValueError, match="Labels must be provided for the metric"):
+        opentelemetry_instance.observe_histogram("num_files_uploaded", 1, dict())
+
+
+def test_multithreaded_singleton():
+    def create_instance():
+        return OpenTelemetry()
+
+    # Create instances in multiple threads
+    with ThreadPoolExecutor(max_workers=10) as executor:
+        futures = [executor.submit(create_instance) for _ in range(100)]
+        instances = [future.result() for future in as_completed(futures)]
+
+    # Check that all instances are the same
+    first_instance = instances[0]
+    for instance in instances[1:]:
+        assert instance is first_instance
+
+
+def test_multithreaded_singleton_race_condition():
+    # This test simulates a potential race condition
+    start_event = threading.Event()
+
+    def create_instance():
+        start_event.wait()  # Wait for all threads to be ready
+        return OpenTelemetry()
+
+    # Create instances in multiple threads, all starting at the same time
+    with ThreadPoolExecutor(max_workers=100) as executor:
+        futures = [executor.submit(create_instance) for _ in range(100)]
+        start_event.set()  # Start all threads simultaneously
+        instances = [future.result() for future in as_completed(futures)]
+
+    # Check that all instances are the same
+    first_instance = instances[0]
+    for instance in instances[1:]:
+        assert instance is first_instance