feat: log retriever endpoint (#2601)

* log retriever endpoint

* disabled by default

* realtime log stream via http/2 SSE

* read and write lock

* unit test

tests/unit/test_logger.py

@@ -0,0 +1,102 @@
+import pytest
+import os
+import json
+from collections import OrderedDict
+from unittest.mock import patch
+from langflow.utils.logger import SizedLogBuffer  # Replace 'your_module' with the actual module name
+
+
+@pytest.fixture
+def sized_log_buffer():
+    return SizedLogBuffer()
+
+
+def test_init_default():
+    buffer = SizedLogBuffer()
+    assert buffer.max == 0
+    assert buffer._max_readers == 20
+    assert isinstance(buffer.buffer, OrderedDict)
+
+
+def test_init_with_env_variable():
+    with patch.dict(os.environ, {"LANGFLOW_LOG_RETRIEVER_BUFFER_SIZE": "100"}):
+        buffer = SizedLogBuffer()
+        assert buffer.max == 100
+
+
+def test_write(sized_log_buffer):
+    message = json.dumps({"text": "Test log", "record": {"time": {"timestamp": 1625097600}}})
+    sized_log_buffer.max = 1  # Set max size to 1 for testing
+    sized_log_buffer.write(message)
+    assert len(sized_log_buffer.buffer) == 1
+    assert 1625097600 in sized_log_buffer.buffer
+    assert sized_log_buffer.buffer[1625097600] == "Test log"
+
+
+def test_write_overflow(sized_log_buffer):
+    sized_log_buffer.max = 2
+    messages = [json.dumps({"text": f"Log {i}", "record": {"time": {"timestamp": 1625097600 + i}}}) for i in range(3)]
+    for message in messages:
+        sized_log_buffer.write(message)
+
+    assert len(sized_log_buffer.buffer) == 2
+    assert 1625097601 in sized_log_buffer.buffer
+    assert 1625097602 in sized_log_buffer.buffer
+
+
+def test_len(sized_log_buffer):
+    sized_log_buffer.max = 3
+    messages = [json.dumps({"text": f"Log {i}", "record": {"time": {"timestamp": 1625097600 + i}}}) for i in range(3)]
+    for message in messages:
+        sized_log_buffer.write(message)
+
+    assert len(sized_log_buffer) == 3
+
+
+def test_get_after_timestamp(sized_log_buffer):
+    sized_log_buffer.max = 5
+    messages = [json.dumps({"text": f"Log {i}", "record": {"time": {"timestamp": 1625097600 + i}}}) for i in range(5)]
+    for message in messages:
+        sized_log_buffer.write(message)
+
+    result = sized_log_buffer.get_after_timestamp(1625097602, lines=2)
+    assert len(result) == 2
+    assert 1625097603 in result
+    assert 1625097602 in result
+
+
+def test_get_before_timestamp(sized_log_buffer):
+    sized_log_buffer.max = 5
+    messages = [json.dumps({"text": f"Log {i}", "record": {"time": {"timestamp": 1625097600 + i}}}) for i in range(5)]
+    for message in messages:
+        sized_log_buffer.write(message)
+
+    result = sized_log_buffer.get_before_timestamp(1625097603, lines=2)
+    assert len(result) == 2
+    assert 1625097601 in result
+    assert 1625097602 in result
+
+
+def test_get_last_n(sized_log_buffer):
+    sized_log_buffer.max = 5
+    messages = [json.dumps({"text": f"Log {i}", "record": {"time": {"timestamp": 1625097600 + i}}}) for i in range(5)]
+    for message in messages:
+        sized_log_buffer.write(message)
+
+    result = sized_log_buffer.get_last_n(3)
+    assert len(result) == 3
+    assert 1625097602 in result
+    assert 1625097603 in result
+    assert 1625097604 in result
+
+
+def test_enabled(sized_log_buffer):
+    assert not sized_log_buffer.enabled()
+    sized_log_buffer.max = 1
+    assert sized_log_buffer.enabled()
+
+
+def test_max_size(sized_log_buffer):
+    assert sized_log_buffer.max_size() == 0
+    sized_log_buffer.max = 100
+    assert sized_log_buffer.max_size() == 100