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378 lines (318 loc) · 13 KB
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"""
Minimal async JSON-RPC 2.0 client for stdio transport
This uses threading to handle blocking IO in an async-friendly way.
Much simpler and more reliable than pure asyncio subprocess.
"""
import asyncio
import inspect
import json
import threading
import uuid
from collections.abc import Awaitable
from typing import Any, Callable, Optional, Union
class JsonRpcError(Exception):
"""JSON-RPC error response"""
def __init__(self, code: int, message: str, data: Any = None):
self.code = code
self.message = message
self.data = data
super().__init__(f"JSON-RPC Error {code}: {message}")
class ProcessExitedError(Exception):
"""Error raised when the CLI process exits unexpectedly"""
pass
RequestHandler = Callable[[dict], Union[dict, Awaitable[dict]]]
class JsonRpcClient:
"""
Minimal async JSON-RPC 2.0 client for stdio transport
Uses threads for blocking IO but provides async interface.
"""
def __init__(self, process):
"""
Create client from subprocess.Popen with stdin/stdout pipes
Args:
process: subprocess.Popen with stdin=PIPE, stdout=PIPE
"""
self.process = process
self.pending_requests: dict[str, asyncio.Future] = {}
self.notification_handler: Optional[Callable[[str, dict], None]] = None
self.request_handlers: dict[str, RequestHandler] = {}
self._running = False
self._read_thread: Optional[threading.Thread] = None
self._stderr_thread: Optional[threading.Thread] = None
self._loop: Optional[asyncio.AbstractEventLoop] = None
self._write_lock = threading.Lock()
self._pending_lock = threading.Lock()
self._process_exit_error: Optional[str] = None
self._stderr_output: list[str] = []
self._stderr_lock = threading.Lock()
def start(self, loop: Optional[asyncio.AbstractEventLoop] = None):
"""Start listening for messages in background thread"""
if not self._running:
self._running = True
# Always use the provided loop or get the running loop
self._loop = loop or asyncio.get_running_loop()
self._read_thread = threading.Thread(target=self._read_loop, daemon=True)
self._read_thread.start()
# Start stderr reader thread if process has stderr
if hasattr(self.process, "stderr") and self.process.stderr:
self._stderr_thread = threading.Thread(target=self._stderr_loop, daemon=True)
self._stderr_thread.start()
def _stderr_loop(self):
"""Read stderr in background to capture error messages"""
try:
while self._running:
if not self.process.stderr:
break
line = self.process.stderr.readline()
if not line:
break
with self._stderr_lock:
self._stderr_output.append(
line.decode("utf-8") if isinstance(line, bytes) else line
)
except Exception:
pass # Ignore errors reading stderr
def get_stderr_output(self) -> str:
"""Get captured stderr output"""
with self._stderr_lock:
return "".join(self._stderr_output).strip()
async def stop(self):
"""Stop listening and clean up"""
self._running = False
if self._read_thread:
self._read_thread.join(timeout=1.0)
if self._stderr_thread:
self._stderr_thread.join(timeout=1.0)
async def request(
self, method: str, params: Optional[dict] = None, timeout: float = 30.0
) -> Any:
"""
Send a JSON-RPC request and wait for response
Args:
method: Method name
params: Optional parameters
timeout: Request timeout in seconds (default 30s)
Returns:
The result from the response
Raises:
JsonRpcError: If server returns an error
asyncio.TimeoutError: If request times out
"""
request_id = str(uuid.uuid4())
# Use the stored loop to ensure consistency with the reader thread
if not self._loop:
raise RuntimeError("Client not started. Call start() first.")
future = self._loop.create_future()
with self._pending_lock:
self.pending_requests[request_id] = future
message = {
"jsonrpc": "2.0",
"id": request_id,
"method": method,
"params": params or {},
}
await self._send_message(message)
try:
return await asyncio.wait_for(future, timeout=timeout)
finally:
with self._pending_lock:
self.pending_requests.pop(request_id, None)
async def notify(self, method: str, params: Optional[dict] = None):
"""
Send a JSON-RPC notification (no response expected)
Args:
method: Method name
params: Optional parameters
"""
message = {
"jsonrpc": "2.0",
"method": method,
"params": params or {},
}
await self._send_message(message)
def set_notification_handler(self, handler: Callable[[str, dict], None]):
"""Set handler for incoming notifications from server"""
self.notification_handler = handler
def set_request_handler(self, method: str, handler: RequestHandler):
if handler is None:
self.request_handlers.pop(method, None)
else:
self.request_handlers[method] = handler
async def _send_message(self, message: dict):
"""Send a JSON-RPC message with Content-Length header"""
loop = self._loop or asyncio.get_event_loop()
def write():
content = json.dumps(message, separators=(",", ":"))
content_bytes = content.encode("utf-8")
header = f"Content-Length: {len(content_bytes)}\r\n\r\n"
with self._write_lock:
self.process.stdin.write(header.encode("utf-8"))
self.process.stdin.write(content_bytes)
self.process.stdin.flush()
# Run in thread pool to avoid blocking
await loop.run_in_executor(None, write)
def _read_loop(self):
"""Read messages from the stream (runs in thread)"""
try:
while self._running:
message = self._read_message()
if message:
self._handle_message(message)
else:
# No message means stream closed - process likely exited
break
except EOFError:
# Stream closed - check if process exited
pass
except Exception as e:
if self._running:
# Store error for pending requests
self._process_exit_error = str(e)
# Process exited or read failed - fail all pending requests
if self._running:
self._fail_pending_requests()
def _fail_pending_requests(self):
"""Fail all pending requests when process exits"""
# Build error message with stderr output
stderr_output = self.get_stderr_output()
return_code = None
if hasattr(self.process, "poll"):
return_code = self.process.poll()
if stderr_output:
error_msg = f"CLI process exited with code {return_code}\nstderr: {stderr_output}"
elif return_code is not None:
error_msg = f"CLI process exited with code {return_code}"
else:
error_msg = "CLI process exited unexpectedly"
# Fail all pending requests
with self._pending_lock:
for request_id, future in list(self.pending_requests.items()):
if not future.done():
exc = ProcessExitedError(error_msg)
loop = future.get_loop()
loop.call_soon_threadsafe(future.set_exception, exc)
def _read_exact(self, num_bytes: int) -> bytes:
"""
Read exactly num_bytes, handling partial/short reads from pipes.
Args:
num_bytes: Number of bytes to read
Returns:
Bytes read from stream
Raises:
EOFError: If stream ends before reading all bytes
"""
chunks = []
remaining = num_bytes
while remaining > 0:
chunk = self.process.stdout.read(remaining)
if not chunk:
raise EOFError("Unexpected end of stream while reading JSON-RPC message")
chunks.append(chunk)
remaining -= len(chunk)
return b"".join(chunks)
def _read_message(self) -> Optional[dict]:
"""
Read a single JSON-RPC message with Content-Length header (blocking)
Returns:
Parsed JSON message or None if connection closed
"""
# Read header line
header_line = self.process.stdout.readline()
if not header_line:
return None
# Parse Content-Length
header = header_line.decode("utf-8").strip()
if not header.startswith("Content-Length:"):
return None
content_length = int(header.split(":")[1].strip())
# Read empty line
self.process.stdout.readline()
# Read exact content using loop to handle short reads
content_bytes = self._read_exact(content_length)
content = content_bytes.decode("utf-8")
return json.loads(content)
def _handle_message(self, message: dict):
"""Handle an incoming message (response or notification)"""
# Check if it's a response to our request
if "id" in message:
with self._pending_lock:
future = self.pending_requests.get(message["id"])
if future is not None:
loop = future.get_loop()
if "error" in message:
error = message["error"]
exc = JsonRpcError(
error.get("code", -1),
error.get("message", "Unknown error"),
error.get("data"),
)
loop.call_soon_threadsafe(future.set_exception, exc)
elif "result" in message:
loop.call_soon_threadsafe(future.set_result, message["result"])
else:
exc = ValueError("Invalid JSON-RPC response")
loop.call_soon_threadsafe(future.set_exception, exc)
return
# Check if it's a notification from server
if "method" in message and "id" not in message:
if self.notification_handler and self._loop:
method = message["method"]
params = message.get("params", {})
# Schedule notification handler on the event loop for thread safety
self._loop.call_soon_threadsafe(self.notification_handler, method, params)
return
# Otherwise handle as incoming request (tool.call, etc.)
if "method" in message and "id" in message:
self._handle_request(message)
def _handle_request(self, message: dict):
handler = self.request_handlers.get(message["method"])
if not handler:
if self._loop:
asyncio.run_coroutine_threadsafe(
self._send_error_response(
message["id"], -32601, f"Method not found: {message['method']}", None
),
self._loop,
)
return
if not self._loop:
return
asyncio.run_coroutine_threadsafe(
self._dispatch_request(message, handler),
self._loop,
)
async def _dispatch_request(self, message: dict, handler: RequestHandler):
try:
params = message.get("params", {})
outcome = handler(params)
if inspect.isawaitable(outcome):
outcome = await outcome
if outcome is None:
outcome = {}
if not isinstance(outcome, dict):
raise ValueError("Request handler must return a dict")
await self._send_response(message["id"], outcome)
except JsonRpcError as exc:
await self._send_error_response(message["id"], exc.code, exc.message, exc.data)
except Exception as exc: # pylint: disable=broad-except
await self._send_error_response(message["id"], -32603, str(exc), None)
async def _send_response(self, request_id: str, result: dict):
response = {
"jsonrpc": "2.0",
"id": request_id,
"result": result,
}
await self._send_message(response)
async def _send_error_response(
self, request_id: str, code: int, message: str, data: Optional[dict]
):
response = {
"jsonrpc": "2.0",
"id": request_id,
"error": {
"code": code,
"message": message,
"data": data,
},
}
await self._send_message(response)
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