fastmcp/tests/server/middleware/test_logging.py
2025-08-26 23:54:34 -05:00

689 lines
24 KiB
Python

"""Tests for logging middleware."""
import datetime
import json
import logging
from typing import Any, Literal, TypeVar
from unittest.mock import AsyncMock, MagicMock
import mcp
import pytest
from inline_snapshot import snapshot
from pydantic import AnyUrl
from fastmcp.resources.template import ResourceTemplate
from fastmcp.server.middleware.logging import (
LoggingMiddleware,
StructuredLoggingMiddleware,
)
from fastmcp.server.middleware.middleware import CallNext, MiddlewareContext
from fastmcp.server.server import FastMCP
FIXED_DATE = datetime.datetime(2023, 1, 1, tzinfo=datetime.timezone.utc)
T = TypeVar("T")
def new_mock_context(
message: T,
method: str | None = None,
source: Literal["server", "client"] | None = None,
type: Literal["request", "notification"] | None = None,
) -> MiddlewareContext[T]:
"""Create a new mock middleware context."""
context = MagicMock(spec=MiddlewareContext[T])
context.method = method or "test_method"
context.source = source or "client"
context.type = type or "request"
context.message = message
context.timestamp = FIXED_DATE
return context
@pytest.fixture
def mock_context():
"""Create a mock middleware context."""
return new_mock_context(
message=mcp.types.CallToolRequest(
method="tools/call",
params=mcp.types.CallToolRequestParams(
name="test_method",
arguments={"param": "value"},
),
)
)
@pytest.fixture
def mock_call_next():
"""Create a mock call_next function."""
return AsyncMock(return_value="test_result")
class TestLoggingMiddleware:
"""Test logging middleware functionality."""
def test_init_default(self):
"""Test default initialization."""
middleware = LoggingMiddleware()
assert middleware.logger.name == "fastmcp.requests"
assert middleware.log_level == logging.INFO
assert middleware.include_payloads is False
assert middleware.max_payload_length == 1000
def test_init_custom(self):
"""Test custom initialization."""
logger = logging.getLogger("custom")
middleware = LoggingMiddleware(
logger=logger,
log_level=logging.DEBUG,
include_payloads=True,
max_payload_length=500,
)
assert middleware.logger is logger
assert middleware.log_level == logging.DEBUG
assert middleware.include_payloads is True
assert middleware.max_payload_length == 500
def test_format_message_without_payloads(
self, mock_context: MiddlewareContext[Any]
):
"""Test message formatting without payloads."""
middleware = LoggingMiddleware()
formatted = middleware._format_message(mock_context)
assert "source=client" in formatted
assert "type=request" in formatted
assert "method=test_method" in formatted
assert "payload=" not in formatted
def test_format_message_with_payloads(self, mock_context: MiddlewareContext[Any]):
"""Test message formatting with payloads."""
middleware = LoggingMiddleware(include_payloads=True)
formatted = middleware._format_message(mock_context)
assert formatted == snapshot(
'source=client type=request method=test_method payload={"method":"tools/call","params":{"_meta":null,"name":"test_method","arguments":{"param":"value"}}}'
)
def test_format_message_long_payload(self, mock_context: MiddlewareContext[Any]):
"""Test message formatting with long payload truncation."""
middleware = LoggingMiddleware(include_payloads=True, max_payload_length=10)
formatted = middleware._format_message(mock_context)
assert "payload=" in formatted
assert "..." in formatted
async def test_on_message_success(
self,
mock_context: MiddlewareContext[Any],
mock_call_next: CallNext[Any, Any],
caplog: pytest.LogCaptureFixture,
):
"""Test logging successful messages."""
middleware = LoggingMiddleware()
with caplog.at_level(logging.INFO):
result = await middleware.on_message(mock_context, mock_call_next)
assert result == "test_result"
assert mock_call_next.called
assert "Processing message:" in caplog.text
assert "Completed message: test_method" in caplog.text
async def test_on_message_failure(
self, mock_context: MiddlewareContext[Any], caplog: pytest.LogCaptureFixture
):
"""Test logging failed messages."""
middleware = LoggingMiddleware()
mock_call_next = AsyncMock(side_effect=ValueError("test error"))
with caplog.at_level(logging.INFO):
with pytest.raises(ValueError):
await middleware.on_message(mock_context, mock_call_next)
assert "Processing message:" in caplog.text
assert "Failed message: test_method - test error" in caplog.text
class TestStructuredLoggingMiddleware:
"""Test structured logging middleware functionality."""
def test_init_default(self):
"""Test default initialization."""
middleware = StructuredLoggingMiddleware()
assert middleware.logger.name == "fastmcp.structured"
assert middleware.log_level == logging.INFO
assert middleware.include_payloads is False
def test_create_log_entry_basic(self, mock_context: MiddlewareContext[Any]):
"""Test creating basic log entry."""
middleware = StructuredLoggingMiddleware()
entry = middleware._create_log_entry(mock_context, "test_event")
assert entry == snapshot(
{
"event": "test_event",
"timestamp": "2023-01-01T00:00:00+00:00",
"source": "client",
"type": "request",
"method": "test_method",
}
)
def test_create_log_entry_with_payload(self, mock_context: MiddlewareContext[Any]):
"""Test creating log entry with payload."""
middleware = StructuredLoggingMiddleware(include_payloads=True)
entry = middleware._create_log_entry(mock_context, "test_event")
assert entry == snapshot(
{
"event": "test_event",
"timestamp": "2023-01-01T00:00:00+00:00",
"source": "client",
"type": "request",
"method": "test_method",
"payload": '{"method":"tools/call","params":{"_meta":null,"name":"test_method","arguments":{"param":"value"}}}',
}
)
def test_create_log_entry_with_extra_fields(
self, mock_context: MiddlewareContext[Any]
):
"""Test creating log entry with extra fields."""
middleware = StructuredLoggingMiddleware()
entry = middleware._create_log_entry(
mock_context, "test_event", extra_field="extra_value"
)
assert entry["extra_field"] == "extra_value"
async def test_on_message_success(
self,
mock_context: MiddlewareContext[Any],
mock_call_next: CallNext[Any, Any],
caplog: pytest.LogCaptureFixture,
):
"""Test structured logging of successful messages."""
middleware = StructuredLoggingMiddleware()
with caplog.at_level(logging.INFO):
result = await middleware.on_message(mock_context, mock_call_next)
assert result == "test_result"
# Check that we have structured JSON logs
log_lines = [record.message for record in caplog.records]
assert len(log_lines) == 2 # start and success entries
assert json.loads(log_lines[0]) == snapshot(
{
"event": "request_start",
"timestamp": "2023-01-01T00:00:00+00:00",
"source": "client",
"type": "request",
"method": "test_method",
}
)
assert json.loads(log_lines[1]) == snapshot(
{
"event": "request_success",
"timestamp": "2023-01-01T00:00:00+00:00",
"source": "client",
"type": "request",
"method": "test_method",
"result_type": "str",
}
)
async def test_on_message_failure(
self, mock_context: MiddlewareContext[Any], caplog: pytest.LogCaptureFixture
):
"""Test structured logging of failed messages."""
middleware = StructuredLoggingMiddleware()
mock_call_next = AsyncMock(side_effect=ValueError("test error"))
with caplog.at_level(logging.INFO):
with pytest.raises(ValueError):
await middleware.on_message(mock_context, mock_call_next)
# Check that we have structured JSON logs
log_lines = [record.message for record in caplog.records]
assert len(log_lines) == 2 # start and error entries
start_entry = json.loads(log_lines[0])
assert start_entry["event"] == "request_start"
assert json.loads(log_lines[1]) == snapshot(
{
"event": "request_error",
"timestamp": "2023-01-01T00:00:00+00:00",
"source": "client",
"type": "request",
"method": "test_method",
"error_type": "ValueError",
"error_message": "test error",
}
)
async def test_on_message_with_pydantic_types_in_payload(
self,
mock_call_next: CallNext[Any, Any],
caplog: pytest.LogCaptureFixture,
):
"""Ensure Pydantic AnyUrl in payload serializes correctly when include_payloads=True."""
mock_context = new_mock_context(
message=mcp.types.ReadResourceRequest(
method="resources/read",
params=mcp.types.ReadResourceRequestParams(
uri=AnyUrl("test://example/1"),
),
)
)
middleware = StructuredLoggingMiddleware(include_payloads=True)
with caplog.at_level(logging.INFO):
result = await middleware.on_message(mock_context, mock_call_next)
assert result == "test_result"
log_lines = [record.message for record in caplog.records]
assert len(log_lines) == 2
assert json.loads(log_lines[0]) == snapshot(
{
"event": "request_start",
"timestamp": "2023-01-01T00:00:00+00:00",
"source": "client",
"type": "request",
"method": "test_method",
"payload": '{"method":"resources/read","params":{"_meta":null,"uri":"test://example/1"}}',
}
)
assert json.loads(log_lines[1]) == snapshot(
{
"event": "request_success",
"timestamp": "2023-01-01T00:00:00+00:00",
"source": "client",
"type": "request",
"method": "test_method",
"result_type": "str",
"payload": '{"method":"resources/read","params":{"_meta":null,"uri":"test://example/1"}}',
}
)
async def test_on_message_with_resource_template_in_payload(
self,
mock_call_next: CallNext[Any, Any],
caplog: pytest.LogCaptureFixture,
):
"""Ensure ResourceTemplate in payload serializes via pydantic conversion without errors."""
mock_context = new_mock_context(
message=ResourceTemplate(
name="tmpl",
uri_template="tmpl://{id}",
parameters={"id": {"type": "string"}},
)
)
middleware = StructuredLoggingMiddleware(include_payloads=True)
with caplog.at_level(logging.INFO):
result = await middleware.on_message(mock_context, mock_call_next)
assert result == "test_result"
log_lines = [record.message for record in caplog.records]
assert len(log_lines) == 2
assert json.loads(log_lines[0]) == snapshot(
{
"event": "request_start",
"timestamp": "2023-01-01T00:00:00+00:00",
"source": "client",
"type": "request",
"method": "test_method",
"payload": '{"name":"tmpl","title":null,"description":null,"tags":[],"meta":null,"enabled":true,"uri_template":"tmpl://{id}","mime_type":"text/plain","parameters":{"id":{"type":"string"}},"annotations":null}',
}
)
async def test_on_message_with_nonserializable_payload_falls_back_to_str(
self, mock_call_next: CallNext[Any, Any], caplog: pytest.LogCaptureFixture
):
"""Ensure non-JSONable objects fall back to string serialization in payload."""
class NonSerializable:
def __str__(self) -> str:
return "NON_SERIALIZABLE"
mock_context = new_mock_context(
message=mcp.types.CallToolRequest(
method="tools/call",
params=mcp.types.CallToolRequestParams(
name="test_method",
arguments={"obj": NonSerializable()},
),
)
)
middleware = StructuredLoggingMiddleware(include_payloads=True)
with caplog.at_level(logging.INFO):
result = await middleware.on_message(mock_context, mock_call_next)
assert result == "test_result"
log_lines = [record.message for record in caplog.records]
assert len(log_lines) >= 2
assert json.loads(log_lines[0]) == snapshot(
{
"event": "request_start",
"timestamp": "2023-01-01T00:00:00+00:00",
"source": "client",
"type": "request",
"method": "test_method",
"payload": '{"method":"tools/call","params":{"_meta":null,"name":"test_method","arguments":{"obj":"NON_SERIALIZABLE"}}}',
}
)
async def test_on_message_with_custom_serializer_applied(
self, mock_call_next: CallNext[Any, Any], caplog: pytest.LogCaptureFixture
):
"""Ensure a custom serializer is used for non-JSONable payloads."""
# Provide a serializer that replaces entire payload with a fixed string
def custom_serializer(_: Any) -> str:
return "CUSTOM_PAYLOAD"
mock_context = new_mock_context(
message=mcp.types.CallToolRequest(
method="tools/call",
params=mcp.types.CallToolRequestParams(
name="test_method",
arguments={"obj": "OBJECT"},
),
)
)
middleware = StructuredLoggingMiddleware(
include_payloads=True, payload_serializer=custom_serializer
)
with caplog.at_level(logging.INFO):
result = await middleware.on_message(mock_context, mock_call_next)
assert result == "test_result"
log_lines = [record.message for record in caplog.records]
assert len(log_lines) >= 2
assert json.loads(log_lines[0]) == snapshot(
{
"event": "request_start",
"timestamp": "2023-01-01T00:00:00+00:00",
"source": "client",
"type": "request",
"method": "test_method",
"payload": "CUSTOM_PAYLOAD",
}
)
@pytest.fixture
def logging_server():
"""Create a FastMCP server specifically for logging middleware tests."""
from fastmcp import FastMCP
mcp = FastMCP("LoggingTestServer")
@mcp.tool
def simple_operation(data: str) -> str:
"""A simple operation for testing logging."""
return f"Processed: {data}"
@mcp.tool
def complex_operation(items: list[str], mode: str = "default") -> dict:
"""A complex operation with structured data."""
return {"processed_items": len(items), "mode": mode, "result": "success"}
@mcp.tool
def operation_with_error(should_fail: bool = False) -> str:
"""An operation that can be made to fail."""
if should_fail:
raise ValueError("Operation failed intentionally")
return "Operation completed successfully"
@mcp.resource("log://test")
def test_resource() -> str:
"""A test resource for logging."""
return "Test resource content"
@mcp.prompt
def test_prompt() -> str:
"""A test prompt for logging."""
return "Test prompt content"
return mcp
class TestLoggingMiddlewareIntegration:
"""Integration tests for logging middleware with real FastMCP server."""
async def test_logging_middleware_logs_successful_operations(
self, logging_server: FastMCP, caplog: pytest.LogCaptureFixture
):
"""Test that logging middleware captures successful operations."""
from fastmcp.client import Client
logging_server.add_middleware(LoggingMiddleware(methods=["tools/call"]))
with caplog.at_level(logging.INFO):
async with Client(logging_server) as client:
await client.call_tool("simple_operation", {"data": "test_data"})
await client.call_tool(
"complex_operation", {"items": ["a", "b", "c"], "mode": "batch"}
)
log_text = caplog.text
# Should have processing and completion logs for both operations
assert "Processing message:" in log_text
assert "Completed message: tools/call" in log_text
# Should have captured both tool calls
processing_count = log_text.count("Processing message:")
completion_count = log_text.count("Completed message:")
assert processing_count == 2
assert completion_count == 2
async def test_logging_middleware_logs_failures(
self, logging_server: FastMCP, caplog: pytest.LogCaptureFixture
):
"""Test that logging middleware captures failed operations."""
from fastmcp.client import Client
logging_server.add_middleware(LoggingMiddleware(methods=["tools/call"]))
with caplog.at_level(logging.INFO):
async with Client(logging_server) as client:
# This should fail and be logged
with pytest.raises(Exception):
await client.call_tool(
"operation_with_error", {"should_fail": True}
)
log_text = caplog.text
# Should have processing and failure logs
assert "Processing message:" in log_text
assert "Failed message: tools/call" in log_text
async def test_logging_middleware_with_payloads(
self, logging_server: FastMCP, caplog: pytest.LogCaptureFixture
):
"""Test logging middleware when configured to include payloads."""
from fastmcp.client import Client
logging_server.add_middleware(
LoggingMiddleware(
include_payloads=True, max_payload_length=500, methods=["tools/call"]
)
)
with caplog.at_level(logging.INFO):
async with Client(logging_server) as client:
await client.call_tool("simple_operation", {"data": "payload_test"})
log_text = caplog.text
# Should include payload information
assert "Processing message:" in log_text
assert "payload=" in log_text
async def test_structured_logging_middleware_produces_json(
self, logging_server: FastMCP, caplog: pytest.LogCaptureFixture
):
"""Test that structured logging middleware produces parseable JSON logs."""
import json
from fastmcp.client import Client
logging_server.add_middleware(
StructuredLoggingMiddleware(include_payloads=True, methods=["tools/call"])
)
with caplog.at_level(logging.INFO):
async with Client(logging_server) as client:
await client.call_tool("simple_operation", {"data": "json_test"})
# Extract JSON log entries
log_lines = [
record.message
for record in caplog.records
if record.name == "fastmcp.structured"
]
assert len(log_lines) >= 2 # Should have start and success entries
# Each log line should be valid JSON
for line in log_lines:
log_entry = json.loads(line)
assert "event" in log_entry
assert "timestamp" in log_entry
assert "source" in log_entry
assert "type" in log_entry
assert "method" in log_entry
async def test_structured_logging_middleware_handles_errors(
self, logging_server: FastMCP, caplog: pytest.LogCaptureFixture
):
"""Test structured logging of errors with JSON format."""
import json
from fastmcp.client import Client
logging_server.add_middleware(
StructuredLoggingMiddleware(methods=["tools/call"])
)
with caplog.at_level(logging.INFO):
async with Client(logging_server) as client:
with pytest.raises(Exception):
await client.call_tool(
"operation_with_error", {"should_fail": True}
)
# Extract JSON log entries
log_lines = [
record.message
for record in caplog.records
if record.name == "fastmcp.structured"
]
# Should have start and error entries
assert len(log_lines) >= 2
# Find the error entry
error_entries = []
for line in log_lines:
log_entry = json.loads(line)
if log_entry.get("event") == "request_error":
error_entries.append(log_entry)
assert len(error_entries) == 1
error_entry = error_entries[0]
assert "error_type" in error_entry
assert "error_message" in error_entry
async def test_logging_middleware_with_different_operations(
self, logging_server: FastMCP, caplog: pytest.LogCaptureFixture
):
"""Test logging middleware with various MCP operations."""
from fastmcp.client import Client
logging_server.add_middleware(
LoggingMiddleware(
methods=[
"tools/call",
"resources/list",
"prompts/get",
"resources/read",
]
)
)
with caplog.at_level(logging.INFO):
async with Client(logging_server) as client:
# Test different operation types
await client.call_tool("simple_operation", {"data": "test"})
await client.read_resource("log://test")
await client.get_prompt("test_prompt")
await client.list_resources()
log_text = caplog.text
# Should have logs for all different operation types
# Note: Different operations may have different method names
processing_count = log_text.count("Processing message:")
completion_count = log_text.count("Completed message:")
# Should have processed all 4 operations
assert processing_count == 4
assert completion_count == 4
async def test_logging_middleware_custom_configuration(
self, logging_server: FastMCP
):
"""Test logging middleware with custom logger configuration."""
import io
import logging
from fastmcp.client import Client
# Create custom logger
log_buffer = io.StringIO()
handler = logging.StreamHandler(log_buffer)
custom_logger = logging.getLogger("custom_logging_test")
custom_logger.addHandler(handler)
custom_logger.setLevel(logging.DEBUG)
logging_server.add_middleware(
LoggingMiddleware(
logger=custom_logger,
log_level=logging.DEBUG,
include_payloads=True,
methods=["tools/call"],
)
)
async with Client(logging_server) as client:
await client.call_tool("simple_operation", {"data": "custom_test"})
# Check that our custom logger captured the logs
log_output = log_buffer.getvalue()
assert "Processing message:" in log_output
assert "payload=" in log_output