# Copyright (C) 2015-2023 The Software Heritage developers
# See the AUTHORS file at the top-level directory of this distribution
# License: GNU General Public License version 3, or any later version
# See top-level LICENSE file for more information
from collections import abc
import functools
import importlib
import inspect
import logging
from typing import (
Any,
Callable,
ClassVar,
Dict,
List,
Optional,
Tuple,
Type,
TypeVar,
Union,
)
import warnings
from deprecated import deprecated
from flask import Flask, Request, Response, abort, request
import requests
import sentry_sdk
from werkzeug.exceptions import HTTPException
from .negotiation import Formatter as FormatterBase
from .negotiation import Negotiator as NegotiatorBase
from .negotiation import negotiate as _negotiate
from .serializers import (
decode_response,
encode_data_client,
exception_to_dict,
json_dumps,
json_loads,
msgpack_dumps,
msgpack_loads,
)
logger = logging.getLogger(__name__)
# support for content negotiation
[docs]
class Negotiator(NegotiatorBase):
[docs]
def best_mimetype(self):
return request.accept_mimetypes.best_match(
self.accept_mimetypes, "application/json"
)
def _abort(self, status_code, err=None):
return abort(status_code, err)
[docs]
def negotiate(formatter_cls, *args, **kwargs):
return _negotiate(Negotiator, formatter_cls, *args, **kwargs)
# base API classes
[docs]
class RemoteException(Exception):
"""raised when remote returned an out-of-band failure notification, e.g., as a
HTTP status code or serialized exception
Attributes:
response: HTTP response corresponding to the failure
"""
def __init__(
self,
payload: Optional[Any] = None,
response: Optional[requests.Response] = None,
):
if payload is not None:
super().__init__(payload)
else:
super().__init__()
self.response = response
def __str__(self):
if (
self.args
and isinstance(self.args[0], dict)
and "type" in self.args[0]
and "args" in self.args[0]
):
return (
f"<RemoteException {self.response.status_code} "
f'{self.args[0]["type"]}: {self.args[0]["args"]}>'
)
else:
return super().__str__()
[docs]
class TransientRemoteException(RemoteException):
"""Subclass of RemoteException representing errors which are expected
to be temporary.
"""
F = TypeVar("F", bound=Callable)
[docs]
def remote_api_endpoint(path: str, method: str = "POST") -> Callable[[F], F]:
def dec(f: F) -> F:
f._endpoint_path = path # type: ignore
f._method = method # type: ignore
return f
return dec
[docs]
class APIError(Exception):
"""API Error"""
def __str__(self):
return "An unexpected error occurred in the backend: {}".format(self.args)
[docs]
class RPCClient(metaclass=MetaRPCClient):
"""Proxy to an internal SWH RPC"""
backend_class = None # type: ClassVar[Optional[type]]
"""For each method of `backend_class` decorated with
:func:`remote_api_endpoint`, a method with the same prototype and
docstring will be added to this class. Calls to this new method will
be translated into HTTP requests to a remote server.
This backend class will never be instantiated, it only serves as
a template."""
api_exception = APIError # type: ClassVar[Type[Exception]]
"""The exception class to raise in case of communication error with
the server."""
reraise_exceptions: ClassVar[List[Type[Exception]]] = []
"""On server errors, if any of the exception classes in this list
has the same name as the error name, then the exception will
be instantiated and raised instead of a generic RemoteException."""
extra_type_encoders: List[Tuple[type, str, Callable]] = []
"""Value of `extra_encoders` passed to `json_dumps` or `msgpack_dumps`
to be able to serialize more object types."""
extra_type_decoders: Dict[str, Callable] = {}
"""Value of `extra_decoders` passed to `json_loads` or `msgpack_loads`
to be able to deserialize more object types."""
def __init__(
self,
url,
api_exception=None,
timeout=None,
chunk_size=4096,
reraise_exceptions=None,
**kwargs,
):
if api_exception:
self.api_exception = api_exception
if reraise_exceptions:
self.reraise_exceptions = reraise_exceptions
base_url = url if url.endswith("/") else url + "/"
self.url = base_url
self.session = requests.Session()
adapter = requests.adapters.HTTPAdapter(
max_retries=kwargs.get("max_retries", 3),
pool_connections=kwargs.get("pool_connections", 20),
pool_maxsize=kwargs.get("pool_maxsize", 100),
)
self.session.mount(self.url, adapter)
self.timeout = timeout
self.chunk_size = chunk_size
def _url(self, endpoint):
return "%s%s" % (self.url, endpoint)
[docs]
def raw_verb(self, verb, endpoint, **opts):
if "chunk_size" in opts:
# if the chunk_size argument has been passed, consider the user
# also wants stream=True, otherwise, what's the point.
opts["stream"] = True
if self.timeout and "timeout" not in opts:
opts["timeout"] = self.timeout
try:
return getattr(self.session, verb)(self._url(endpoint), **opts)
except requests.exceptions.ConnectionError as e:
raise self.api_exception(e)
def _post(self, endpoint, data, **opts):
if isinstance(data, (abc.Iterator, abc.Generator)):
data = (self._encode_data(x) for x in data)
else:
data = self._encode_data(data)
chunk_size = opts.pop("chunk_size", self.chunk_size)
response = self.raw_verb(
"post",
endpoint,
data=data,
headers={
"content-type": "application/x-msgpack",
"accept": "application/x-msgpack",
},
**opts,
)
if opts.get("stream") or response.headers.get("transfer-encoding") == "chunked":
self.raise_for_status(response)
return response.iter_content(chunk_size)
else:
return self._decode_response(response)
def _encode_data(self, data):
return encode_data_client(data, extra_encoders=self.extra_type_encoders)
_post_stream = _post
[docs]
@deprecated(version="2.1.0", reason="Use _post instead")
def post(self, *args, **kwargs):
return self._post(*args, **kwargs)
[docs]
@deprecated(version="2.1.0", reason="Use _post_stream instead")
def post_stream(self, *args, **kwargs):
return self._post_stream(*args, **kwargs)
def _get(self, endpoint, **opts):
chunk_size = opts.pop("chunk_size", self.chunk_size)
response = self.raw_verb(
"get", endpoint, headers={"accept": "application/x-msgpack"}, **opts
)
if opts.get("stream") or response.headers.get("transfer-encoding") == "chunked":
self.raise_for_status(response)
return response.iter_content(chunk_size)
else:
return self._decode_response(response)
def _get_stream(self, endpoint, **opts):
return self._get(endpoint, stream=True, **opts)
[docs]
@deprecated(version="2.1.0", reason="Use _get instead")
def get(self, *args, **kwargs):
return self._get(*args, **kwargs)
[docs]
@deprecated(version="2.1.0", reason="Use _get_stream instead")
def get_stream(self, *args, **kwargs):
return self._get_stream(*args, **kwargs)
[docs]
def raise_for_status(self, response) -> None:
"""check response HTTP status code and raise an exception if it denotes an
error; do nothing otherwise
"""
status_code = response.status_code
status_class = response.status_code // 100
if status_code == 404:
raise RemoteException(payload="404 not found", response=response)
exception = None
if status_class == 4:
exc_data = self._decode_response(response, check_status=False)
if isinstance(exc_data, dict):
for exc_type in self.reraise_exceptions:
if exc_type.__name__ == exc_data["type"]:
exception = exc_type(*exc_data["args"])
break
else:
exception = RemoteException(payload=exc_data, response=response)
else:
# Typically, because the error is from a reverse proxy not aware of this
# RPC protocol, so response's content-type is text/html
exception = APIError(exc_data, response)
elif status_class == 5:
cls: Type[RemoteException]
if status_code in (502, 503):
# This isn't a generic HTTP client and we know the server does
# not support the Retry-After header, so we do not implement
# it here either.
cls = TransientRemoteException
else:
cls = RemoteException
exc_data = self._decode_response(response, check_status=False)
exception = cls(payload=exc_data, response=response)
if exception:
raise exception from None
if status_class != 2:
raise RemoteException(
payload=f"API HTTP error: {status_code} {response.content}",
response=response,
)
def _decode_response(self, response, check_status=True):
if check_status:
self.raise_for_status(response)
return decode_response(response, extra_decoders=self.extra_type_decoders)
def __repr__(self):
return "<{} url={}>".format(self.__class__.__name__, self.url)
[docs]
class BytesRequest(Request):
"""Request with proper escaping of arbitrary byte sequences."""
encoding = "utf-8"
encoding_errors = "surrogateescape"
ENCODERS: Dict[str, Callable[[Any], Union[bytes, str]]] = {
"application/x-msgpack": msgpack_dumps,
"application/json": json_dumps,
}
[docs]
def encode_data_server(
data, content_type="application/x-msgpack", extra_type_encoders=None
):
encoded_data = ENCODERS[content_type](data, extra_encoders=extra_type_encoders)
return Response(
encoded_data,
mimetype=content_type,
)
[docs]
def decode_request(request, extra_decoders=None):
content_type = request.mimetype
data = request.get_data()
if not data:
return {}
if content_type == "application/x-msgpack":
r = msgpack_loads(data, extra_decoders=extra_decoders)
elif content_type == "application/json":
# XXX this .decode() is needed for py35.
# Should not be needed any more with py37
r = json_loads(data.decode("utf-8"), extra_decoders=extra_decoders)
else:
raise ValueError("Wrong content type `%s` for API request" % content_type)
return r
[docs]
def error_handler(
exception: BaseException, encoder=encode_data_server, status_code: int = 500
):
"""Error handler to be registered using flask's error-handling decorator
``app.errorhandler``.
This is used for exceptions that are expected in the normal execution flow of the
RPC-ed API, in which case the status code should be set to a value in the 4xx range,
as well as for exceptions that are unexpected (generally, a bare
:class:`Exception`), and for which the status code should be kept in the 5xx class.
This function only captures exceptions as sentry errors if the status code is in the
5xx range and not 502/503/504, as "expected exceptions" in the 4xx range are more,
likely to be handled on the client side; and 502/503/504 are "transient" exceptions
that should be resolved with client retries.
"""
status_class = status_code // 100
if status_class == 5 and status_code not in (502, 503, 504):
logger.exception(exception)
sentry_sdk.capture_exception(exception)
response = encoder(exception_to_dict(exception))
if isinstance(exception, HTTPException):
response.status_code = exception.code
else:
response.status_code = status_code
return response
[docs]
class RPCServerApp(Flask):
"""For each endpoint of the given `backend_class`, tells app.route to call
a function that decodes the request and sends it to the backend object
provided by the factory.
:param Any backend_class:
The class of the backend, which will be analyzed to look
for API endpoints.
:param Optional[Callable[[], backend_class]] backend_factory:
A function with no argument that returns an instance of
`backend_class`. If unset, defaults to calling `backend_class`
constructor directly.
For each method 'do_x()' of the ``backend_factory``, subclasses may implement
two methods: ``pre_do_x(self, kw)`` and ``post_do_x(self, ret, kw)`` that will
be called respectively before and after ``do_x(**kw)``. ``kw`` is the dict
of request parameters, and ``ret`` is the return value of ``do_x(**kw)``.
"""
request_class = BytesRequest
extra_type_encoders: List[Tuple[type, str, Callable]] = []
"""Value of `extra_encoders` passed to `json_dumps` or `msgpack_dumps`
to be able to serialize more object types."""
extra_type_decoders: Dict[str, Callable] = {}
"""Value of `extra_decoders` passed to `json_loads` or `msgpack_loads`
to be able to deserialize more object types."""
method_decorators: List[Callable[[Callable], Callable]] = []
"""List of decorators to all methods generated from the ``backend_class``."""
exception_status_codes: List[Tuple[Union[Type[BaseException], str], int]] = [
# Default to "Internal Server Error" for most exceptions:
(Exception, 500),
# These errors are noisy, and are better logged on the caller's side after
# it retried a few times:
("psycopg2.errors.OperationalError", 503),
# Subclass of OperationalError; but it is unlikely to be solved after retries
# (short of getting more cache hits) because this is usually caused by the query
# size instead of a transient failure
("psycopg2.errors.QueryCanceled", 500),
# Often a transient error because of connectivity issue with, or restart of,
# the Kafka brokers:
("swh.journal.writer.kafka.KafkaDeliveryError", 503),
]
"""Pairs of ``(exception, status_code)`` where ``exception`` is either an
exception class or a a dotted exception name to be imported (and ignored if import
fails) and ``status_code`` is the HTTP code that should be returned when an instance
of this exception is raised.
If a raised exception is an instance of a subclass of two classes defined here,
the most specific class wins, according Flask's MRO-based resolution."""
def __init__(self, *args, backend_class=None, backend_factory=None, **kwargs):
super().__init__(*args, **kwargs)
self.add_backend_class(backend_class, backend_factory)
self._register_error_handlers()
def _register_error_handlers(self):
for exception, status_code in self.exception_status_codes:
if isinstance(exception, str):
(module_path, class_name) = exception.rsplit(".", 1)
try:
module = importlib.import_module(module_path, package=__package__)
except ImportError as e:
logger.debug("Could not import %s: %r", exception, e)
continue
exception = getattr(module, class_name)
self.register_error_handler(
exception, functools.partial(error_handler, status_code=status_code)
)
[docs]
def add_backend_class(self, backend_class=None, backend_factory=None):
if backend_class is None and backend_factory is not None:
raise ValueError(
"backend_factory should only be provided if backend_class is"
)
if backend_class is not None:
backend_factory = backend_factory or backend_class
for meth_name, meth in backend_class.__dict__.items():
if hasattr(meth, "_endpoint_path"):
self.__add_endpoint(meth_name, meth, backend_factory)
def __add_endpoint(self, meth_name, meth, backend_factory):
from flask import request
@negotiate(MsgpackFormatter, extra_encoders=self.extra_type_encoders)
@negotiate(JSONFormatter, extra_encoders=self.extra_type_encoders)
@functools.wraps(meth) # Copy signature and doc
def f():
# Call the actual code
pre_hook = getattr(self, f"pre_{meth_name}", None)
post_hook = getattr(self, f"post_{meth_name}", None)
obj_meth = getattr(backend_factory(), meth_name)
kw = decode_request(request, extra_decoders=self.extra_type_decoders)
if pre_hook is not None:
pre_hook(kw)
ret = obj_meth(**kw)
if post_hook is not None:
post_hook(ret, kw)
return ret
for decorator in self.method_decorators:
f = decorator(f)
self.route("/" + meth._endpoint_path, methods=["POST"])(f)
[docs]
def setup_psycopg2_errorhandlers(self) -> None:
"""Deprecated method; error handlers are now setup in the constructor."""
warnings.warn(
"setup_psycopg2_errorhandlers has no effect; error handlers are now setup "
"by the constructor.",
DeprecationWarning,
)
