"""
本模块提供基于Http轮训的后端通用类和函数
.. attention::
PyWebIO 的会话状态保存在进程内，所以不支持多进程部署的后端服务
比如使用 ``uWSGI`` 部署后端服务，并使用 ``--processes n`` 选项设置了多进程；
或者使用 ``nginx`` 等反向代理将流量负载到多个后端副本上。
A note on run backend server with uWSGI：
If you start uWSGI without threads, the Python GIL will not be enabled,
so threads generated by your application will never run.
`uWSGI doc <https://uwsgi-docs.readthedocs.io/en/latest/WSGIquickstart.html#a-note-on-python-threads>`_
"""
import asyncio
import fnmatch
import logging
import threading
from typing import Dict
import time
from .utils import make_applications, render_page
from ..session import CoroutineBasedSession, Session, ThreadBasedSession, register_session_implement_for_target
from ..session.base import get_session_info_from_headers
from ..utils import random_str, LRUDict, isgeneratorfunction, iscoroutinefunction, check_webio_js
class HttpContext:
"""一次Http请求的上下文， 不同的后端框架需要根据框架提供的方法实现本类的方法"""
backend_name = '' # 当前使用的Web框架名
def request_obj(self):
"""返回当前请求对象"""
pass
def request_method(self):
"""返回当前请求的方法，大写"""
pass
def request_headers(self):
"""返回当前请求的header字典"""
pass
def request_url_parameter(self, name, default=None):
"""返回当前请求的URL参数"""
pass
def request_json(self) -> dict:
"""返回当前请求的json反序列化后的内容，若请求数据不为json格式，返回None"""
pass
def set_header(self, name, value):
"""为当前响应设置header"""
pass
def set_status(self, status):
"""为当前响应设置http status"""
pass
def set_content(self, content, json_type=False):
"""设置响应的内容。方法应该仅被调用一次
:param str/bytes/json-able content:
:param bool json_type: content是否要序列化成json格式，并将 content-type 设置为application/json
"""
pass
def get_response(self):
"""获取当前的响应对象，用于在视图函数中返回"""
pass
def get_client_ip(self):
"""获取用户的ip"""
pass
logger = logging.getLogger(__name__)
_event_loop = None
# todo: use lock to avoid thread race condition
[文档]class HttpHandler:
"""基于HTTP的后端Handler实现
.. note::
对 HttpHandler._webio_sessions 的访问不需要加锁, See：
https://stackoverflow.com/questions/1312331/using-a-global-dictionary-with-threads-in-python
"""
# type: Dict[str, Session]
_webio_sessions = {} # WebIOSessionID -> WebIOSession()
_webio_expire = LRUDict() # WebIOSessionID -> last active timestamp。按照最后活跃时间递增排列
_webio_expire_lock = threading.Lock()
_last_check_session_expire_ts = 0 # 上次检查session有效期的时间戳
WAIT_MS_ON_POST = 100 # 在处理完POST请求时，等待WAIT_MS_ON_POST毫秒再读取返回数据。Task的command可以立即返回
DEFAULT_SESSION_EXPIRE_SECONDS = 60 # 默认会话过期时间
DEFAULT_SESSIONS_CLEANUP_INTERVAL = 20 # 默认清理过期会话间隔（秒）
@classmethod
def _remove_expired_sessions(cls, session_expire_seconds):
"""清除当前会话列表中的过期会话"""
logger.debug("removing expired sessions")
while cls._webio_expire:
sid, active_ts = cls._webio_expire.popitem(last=False) # 弹出最不活跃的session info
if time.time() - active_ts < session_expire_seconds:
# 当前session未过期
cls._webio_expire[sid] = active_ts
cls._webio_expire.move_to_end(sid, last=False)
break
# 清理session
logger.debug("session %s expired" % sid)
session = cls._webio_sessions.get(sid)
if session:
session.close()
del cls._webio_sessions[sid]
@classmethod
def _remove_webio_session(cls, sid):
cls._webio_sessions.pop(sid, None)
cls._webio_expire.pop(sid, None)
def _process_cors(self, context: HttpContext):
"""处理跨域请求：检查请求来源并根据可访问性设置headers"""
origin = context.request_headers().get('Origin', '')
if self.check_origin(origin):
context.set_header('Access-Control-Allow-Origin', origin)
context.set_header('Access-Control-Allow-Methods', 'GET, POST')
context.set_header('Access-Control-Allow-Headers', 'content-type, webio-session-id')
context.set_header('Access-Control-Expose-Headers', 'webio-session-id')
context.set_header('Access-Control-Max-Age', str(1440 * 60))
def interval_cleaning(self):
# clean up at intervals
cls = type(self)
need_clean = False
with cls._webio_expire_lock:
if time.time() - cls._last_check_session_expire_ts > self.session_cleanup_interval:
cls._last_check_session_expire_ts = time.time()
need_clean = True
if need_clean:
cls._remove_expired_sessions(self.session_expire_seconds)
[文档] def handle_request(self, context: HttpContext):
"""处理请求"""
cls = type(self)
if _event_loop:
asyncio.set_event_loop(_event_loop)
request_headers = context.request_headers()
# CORS process start ############################
if context.request_method() == 'OPTIONS': # preflight request for CORS
self._process_cors(context)
context.set_status(204)
return context.get_response()
if request_headers.get('Origin'): # set headers for CORS request
self._process_cors(context)
# CORS process end ############################
if context.request_url_parameter('test'): # 测试接口，当会话使用基于http的backend时，返回 ok
context.set_content('ok')
return context.get_response()
# 对首页HTML的请求
if 'webio-session-id' not in request_headers:
app_name = context.request_url_parameter('app', 'index')
app = self.applications.get(app_name) or self.applications['index']
html = render_page(app, protocol='http', cdn=self.cdn)
context.set_content(html)
return context.get_response()
webio_session_id = None
# 初始请求，创建新 Session
if not request_headers['webio-session-id'] or request_headers['webio-session-id'] == 'NEW':
if context.request_method() == 'POST': # 不能在POST请求中创建Session，防止CSRF攻击
context.set_status(403)
return context.get_response()
webio_session_id = random_str(24)
context.set_header('webio-session-id', webio_session_id)
session_info = get_session_info_from_headers(context.request_headers())
session_info['user_ip'] = context.get_client_ip()
session_info['request'] = context.request_obj()
session_info['backend'] = context.backend_name
app_name = context.request_url_parameter('app', 'index')
application = self.applications.get(app_name) or self.applications['index']
if iscoroutinefunction(application) or isgeneratorfunction(application):
session_cls = CoroutineBasedSession
else:
session_cls = ThreadBasedSession
webio_session = session_cls(application, session_info=session_info)
cls._webio_sessions[webio_session_id] = webio_session
time.sleep(cls.WAIT_MS_ON_POST / 1000.0) # 等待session输出完毕
elif request_headers['webio-session-id'] not in cls._webio_sessions: # WebIOSession deleted
context.set_content([dict(command='close_session')], json_type=True)
return context.get_response()
else:
webio_session_id = request_headers['webio-session-id']
webio_session = cls._webio_sessions[webio_session_id]
if context.request_method() == 'POST': # client push event
if context.request_json() is not None:
webio_session.send_client_event(context.request_json())
time.sleep(cls.WAIT_MS_ON_POST / 1000.0) # 等待session输出完毕
elif context.request_method() == 'GET': # client pull messages
pass
cls._webio_expire[webio_session_id] = time.time()
self.interval_cleaning()
context.set_content(webio_session.get_task_commands(), json_type=True)
if webio_session.closed():
self._remove_webio_session(webio_session_id)
return context.get_response()
def __init__(self, applications, cdn,
session_expire_seconds=None,
session_cleanup_interval=None,
allowed_origins=None, check_origin=None):
"""获取用于与后端实现进行整合的view函数，基于http请求与前端进行通讯
:param list/dict/callable applications: PyWebIO应用. 可以是任务函数或者任务函数的字典或列表。
:param bool/str cdn: 是否从CDN加载前端静态资源. 支持传入URL来自定义CDN地址。
:param int session_expire_seconds: 会话不活跃过期时间。
:param int session_cleanup_interval: 会话清理间隔。
:param list allowed_origins: 除当前域名外，服务器还允许的请求的来源列表。
来源包含协议和域名和端口部分，允许使用 Unix shell 风格的匹配模式:
- ``*`` 为通配符
- ``?`` 匹配单个字符
- ``[seq]`` 匹配seq内的字符
- ``[!seq]`` 匹配不在seq内的字符
比如 ``https://*.example.com`` 、 ``*://*.example.com``
:param callable check_origin: 请求来源检查函数。接收请求来源(包含协议和域名和端口部分)字符串，
返回 ``True/False`` 。若设置了 ``check_origin`` ， ``allowed_origins`` 参数将被忽略
"""
check_webio_js()
cls = type(self)
self.cdn = cdn
self.applications = make_applications(applications)
self.check_origin = check_origin
self.session_expire_seconds = session_expire_seconds or cls.DEFAULT_SESSION_EXPIRE_SECONDS
self.session_cleanup_interval = session_cleanup_interval or cls.DEFAULT_SESSIONS_CLEANUP_INTERVAL
for target in self.applications.values():
register_session_implement_for_target(target)
if check_origin is None:
self.check_origin = lambda origin: any(
fnmatch.fnmatch(origin, patten)
for patten in allowed_origins or []
)
[文档]def run_event_loop(debug=False):
"""运行事件循环
基于协程的会话在启动基于线程的http服务器之前需要启动一个单独的线程来运行事件循环。
:param debug: Set the debug mode of the event loop.
See also: https://docs.python.org/3/library/asyncio-dev.html#asyncio-debug-mode
"""
global _event_loop
CoroutineBasedSession.event_loop_thread_id = threading.current_thread().ident
_event_loop = asyncio.new_event_loop()
_event_loop.set_debug(debug)
asyncio.set_event_loop(_event_loop)
_event_loop.run_forever()