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iostream.py
A utility class to write to and read from a non-blocking socket.
IOStream 对 socket 进行包装，采用注册回调方式实现非阻塞。通过接口注册各个事件回调
_read_callback
_write_callback
_close_callback
_connect_callback
ioloop 中 socket 事件发生后，调用 IOStream._handle_events 方法，对事件进行分发。对应的事件处理过程中，如果满足注册的回调条件，则调用回调函数 回调函数在 IOStream._handle_events 中被调用
contents
iostream.py
contents
example
head
IOStream.__init__
IOStream.connect
IOStream.read_until
IOStream.read_bytes
IOStream.write
IOStream.close
IOStream._handle_events
IOStream._run_callback
IOStream._run_callback
IOStream._read_from_socket
IOStream._read_to_buffer
IOStream._read_from_buffer
IOStream._handle_connect
IOStream._handle_write
IOStream._consume
IOStream._add_io_state
IOStream._read_buffer_size
copyright
example
一个简单的 IOStream 客户端示例 由此可见，IOStream 是一个异步回调链
创建 socket
创建 IOStream 对象
连接到主机，传入连接成功后回调函数 send_request
socket 输出数据请求页面，读取 head, 传入读取 head 成功后回调函数 on_headers
继续读取 body, 传入读取 body 成功后回调函数 on_body
关闭 stream，关闭 ioloop
from tornado import ioloop
from tornado import iostream
import socket
def send_request():
stream.write(“GET / HTTP/1.0\r\nHost: baidu.com\r\n\r\n”)
stream.read_until(“\r\n\r\n”, on_headers)
def on_headers(data):
headers = {}
for line in data.split(“\r\n”):
parts = line.split(“:”)
if len(parts) == 2:
headers[parts[0].strip()] = parts[1].strip()
stream.read_bytes(int(headers[“Content-Length”]), on_body)
def on_body(data):
print data
stream.close()
ioloop.IOLoop.instance().stop()
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM, 0)
stream = iostream.IOStream(s)
stream.connect((“baidu.com”, 80), send_request)
ioloop.IOLoop.instance().start()
# html>
# <meta http-equiv=”refresh” content=”0; url=http://www.baidu.com/”>
# </html>
head
from __future__ import with_statement
import collections
import errno
import logging
import socket
import sys
from tornado import ioloop
from tornado import stack_context
try:
import ssl # Python 2.6+
except ImportError:
ssl = None
IOStream.__init__
包装 socket 类 关键语句 self.io_loop.add_handler(self.socket.fileno(), self._handle_events, self._state) 将自身的_handle_events 加入到全局 ioloop poll 事件回调 此时只注册了 ERROR 类型事件
_read_buffer: 读缓冲
class IOStream(object):
def __init__(self, socket, io_loop=None, max_buffer_size=104857600,
read_chunk_size=4096):
self.socket = socket
self.socket.setblocking(False)
self.io_loop = io_loop or ioloop.IOLoop.instance()
self.max_buffer_size = max_buffer_size
self.read_chunk_size = read_chunk_size
self._read_buffer = collections.deque()
self._write_buffer = collections.deque()
self._write_buffer_frozen = False
self._read_delimiter = None
self._read_bytes = None
self._read_callback = None
self._write_callback = None
self._close_callback = None
self._connect_callback = None
self._connecting = False
self._state = self.io_loop.ERROR
with stack_context.NullContext():
self.io_loop.add_handler(
self.socket.fileno(), self._handle_events, self._state)
IOStream.connect
连接 socket 到远程地址，非阻塞模式
连接 socket
注册连接完成回调
poll 增加 socket 写事件
def connect(self, address, callback=None):
“””Connects the socket to a remote address without blocking.
May only be called if the socket passed to the constructor was
not previously connected. The address parameter is in the
same format as for socket.connect, i.e. a (host, port) tuple.
If callback is specified, it will be called when the
connection is completed.
Note that it is safe to call IOStream.write while the
connection is pending, in which case the data will be written
as soon as the connection is ready. Calling IOStream read
methods before the socket is connected works on some platforms
but is non-portable.
“””
self._connecting = True
try:
self.socket.connect(address)
except socket.error, e:
# In non-blocking mode connect() always raises an exception
if e.args[0] not in (errno.EINPROGRESS, errno.EWOULDBLOCK):
raise
self._connect_callback = stack_context.wrap(callback)
self._add_io_state(self.io_loop.WRITE)
IOStream.read_until
注册读完成回调
尝试从缓冲中读
从 socket 中读到缓冲区
重复 2,3, 没有数据则退出
将 socket 读事件加入 poll
如果缓存中数据满足条件，则直接执行 callback 并返回，否则，保存 callback 函数下次 read 事件发生时，_handle_events 处理读事件时，再进行检测及调用
def read_until(self, delimiter, callback):
“””Call callback when we read the given delimiter.”””
assert not self._read_callback, “Already reading”
self._read_delimiter = delimiter
self._read_callback = stack_context.wrap(callback)
while True:
# See if we’ve already got the data from a previous read
if self._read_from_buffer():
return
self._check_closed()
if self._read_to_buffer() == 0:
break
self._add_io_state(self.io_loop.READ)
IOStream.read_bytes
参考 read_until，读限定字节
def read_bytes(self, num_bytes, callback):
“””Call callback when we read the given number of bytes.”””
assert not self._read_callback, “Already reading”
if num_bytes == 0:
callback(“”)
return
self._read_bytes = num_bytes
self._read_callback = stack_context.wrap(callback)
while True:
if self._read_from_buffer():
return
self._check_closed()
if self._read_to_buffer() == 0:
break
self._add_io_state(self.io_loop.READ)
IOStream.write
def write(self, data, callback=None):
“””Write the given data to this stream.
If callback is given, we call it when all of the buffered write
data has been successfully written to the stream. If there was
previously buffered write data and an old write callback, that
callback is simply overwritten with this new callback.
“””
self._check_closed()
self._write_buffer.append(data)
self._add_io_state(self.io_loop.WRITE)
self._write_callback = stack_context.wrap(callback)
def set_close_callback(self, callback):
“””Call the given callback when the stream is closed.”””
self._close_callback = stack_context.wrap(callback)
IOStream.close
从 ioloop 移除 socket 事件
关闭 socket
调用关闭回调
def close(self):
“””Close this stream.”””
if self.socket is not None:
self.io_loop.remove_handler(self.socket.fileno())
self.socket.close()
self.socket = None
if self._close_callback:
self._run_callback(self._close_callback)
def reading(self):
“””Returns true if we are currently reading from the stream.”””
return self._read_callback is not None
def writing(self):
“””Returns true if we are currently writing to the stream.”””
return bool(self._write_buffer)
def closed(self):
return self.socket is None
IOStream._handle_events
核心回调 任何类型的 socket 事件触发 ioloop 回调_handle_events，然后在_handle_events 再进行分发 值得注意的是，IOStream 不处理连接请求的 read 事件 注意 作为服务端，默认代理的是已经建立连接的 socket
# HTTPServer.\_handle_events
# connection 为已经 accept 的连接
stream = iostream.IOStream(connection, io_loop=self.io_loop)
作为客户端，需要手动调用 IOStream.connect，连接成功后，成功回调在 write 事件中处理
这个实现比较别扭
def _handle_events(self, fd, events):
if not self.socket:
logging.warning(“Got events for closed stream %d”, fd)
return
try:
# 处理读事件，调用已注册回调
if events & self.io_loop.READ:
self._handle_read()
if not self.socket:
return
# 处理写事件，如果是刚建立连接，调用连接建立回调
if events & self.io_loop.WRITE:
if self._connecting:
self._handle_connect()
self._handle_write()
if not self.socket:
return
# 错误事件，关闭 socket
if events & self.io_loop.ERROR:
self.close()
return
state = self.io_loop.ERROR
if self.reading():
state |= self.io_loop.READ
if self.writing():
state |= self.io_loop.WRITE
if state != self._state:
self._state = state
self.io_loop.update_handler(self.socket.fileno(), self._state)
except:
logging.error(“Uncaught exception, closing connection.”,
exc_info=True)
self.close()
raise
IOStream._run_callback
执行回调
def _run_callback(self, callback, *args, **kwargs):
try:
# Use a NullContext to ensure that all StackContexts are run
# inside our blanket exception handler rather than outside.
with stack_context.NullContext():
callback(*args, **kwargs)
except:
logging.error(“Uncaught exception, closing connection.”,
exc_info=True)
# Close the socket on an uncaught exception from a user callback
# (It would eventually get closed when the socket object is
# gc’d, but we don’t want to rely on gc happening before we
# run out of file descriptors)
self.close()
# Re-raise the exception so that IOLoop.handle_callback_exception
# can see it and log the error
raise
IOStream._run_callback
读回调
从 socket 读取数据到缓存
无数据,socket 关闭
检测是否满足 read_until read_bytes
满足则执行对应回调
def _handle_read(self):
while True:
try:
# Read from the socket until we get EWOULDBLOCK or equivalent.
# SSL sockets do some internal buffering, and if the data is
# sitting in the SSL object’s buffer select() and friends
# can’t see it; the only way to find out if it’s there is to
# try to read it.
result = self._read_to_buffer()
except Exception:
self.close()
return
if result == 0:
break
else:
if self._read_from_buffer():
return
IOStream._read_from_socket
从 socket 读取数据
def _read_from_socket(self):
“””Attempts to read from the socket.
Returns the data read or None if there is nothing to read.
May be overridden in subclasses.
“””
try:
chunk = self.socket.recv(self.read_chunk_size)
except socket.error, e:
if e.args[0] in (errno.EWOULDBLOCK, errno.EAGAIN):
return None
else:
raise
if not chunk:
self.close()
return None
return chunk
IOStream._read_to_buffer
从 socket 读取数据存入缓存
def _read_to_buffer(self):
“””Reads from the socket and appends the result to the read buffer.
Returns the number of bytes read. Returns 0 if there is nothing
to read (i.e. the read returns EWOULDBLOCK or equivalent). On
error closes the socket and raises an exception.
“””
try:
chunk = self._read_from_socket()
except socket.error, e:
# ssl.SSLError is a subclass of socket.error
logging.warning(“Read error on %d: %s”,
self.socket.fileno(), e)
self.close()
raise
if chunk is None:
return 0
self._read_buffer.append(chunk)
if self._read_buffer_size() >= self.max_buffer_size:
logging.error(“Reached maximum read buffer size”)
self.close()
raise IOError(“Reached maximum read buffer size”)
return len(chunk)
IOStream._read_from_buffer
从缓冲中过滤数据 检测是否满足结束条件 (read_until/read_bytes)，满足则调用之前注册的回调 采用的是查询方式
def _read_from_buffer(self):
“””Attempts to complete the currently-pending read from the buffer.
Returns True if the read was completed.
“””
if self._read_bytes:
if self._read_buffer_size() >= self._read_bytes:
num_bytes = self._read_bytes
callback = self._read_callback
self._read_callback = None
self._read_bytes = None
self._run_callback(callback, self._consume(num_bytes))
return True
elif self._read_delimiter:
_merge_prefix(self._read_buffer, sys.maxint)
loc = self._read_buffer[0].find(self._read_delimiter)
if loc != -1:
callback = self._read_callback
delimiter_len = len(self._read_delimiter)
self._read_callback = None
self._read_delimiter = None
self._run_callback(callback,
self._consume(loc + delimiter_len))
return True
return False
IOStream._handle_connect
调用连接建立回调，并清除连接中标志
def _handle_connect(self):
if self._connect_callback is not None:
callback = self._connect_callback
self._connect_callback = None
self._run_callback(callback)
self._connecting = False
IOStream._handle_write
写事件
从缓冲区获取限定范围内数据
调用 socket.send 输出数据
如果数据发送我且已注册回调，调用发送完成回调
def _handle_write(self):
while self._write_buffer:
try:
if not self._write_buffer_frozen:
# On windows, socket.send blows up if given a
# write buffer that’s too large, instead of just
# returning the number of bytes it was able to
# process. Therefore we must not call socket.send
# with more than 128KB at a time.
_merge_prefix(self._write_buffer, 128 * 1024)
num_bytes = self.socket.send(self._write_buffer[0])
self._write_buffer_frozen = False
_merge_prefix(self._write_buffer, num_bytes)
self._write_buffer.popleft()
except socket.error, e:
if e.args[0] in (errno.EWOULDBLOCK, errno.EAGAIN):
# With OpenSSL, after send returns EWOULDBLOCK,
# the very same string object must be used on the
# next call to send. Therefore we suppress
# merging the write buffer after an EWOULDBLOCK.
# A cleaner solution would be to set
# SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER, but this is
# not yet accessible from python
# (http://bugs.python.org/issue8240)
self._write_buffer_frozen = True
break
else:
logging.warning(“Write error on %d: %s”,
self.socket.fileno(), e)
self.close()
return
if not self._write_buffer and self._write_callback:
callback = self._write_callback
self._write_callback = None
self._run_callback(callback)
IOStream._consume
从读缓存消费 loc 长度的数据
def _consume(self, loc):
_merge_prefix(self._read_buffer, loc)
return self._read_buffer.popleft()
def _check_closed(self):
if not self.socket:
raise IOError(“Stream is closed”)
IOStream._add_io_state
增加 socket 事件状态
def _add_io_state(self, state):
if self.socket is None:
# connection has been closed, so there can be no future events
return
if not self._state & state:
self._state = self._state | state
self.io_loop.update_handler(self.socket.fileno(), self._state)
IOStream._read_buffer_size
获取读缓存中已有数据长度
def _read_buffer_size(self):
return sum(len(chunk) for chunk in self._read_buffer)
class SSLIOStream(IOStream):
“””A utility class to write to and read from a non-blocking socket.
If the socket passed to the constructor is already connected,
it should be wrapped with
ssl.wrap_socket(sock, do_handshake_on_connect=False, **kwargs)
before constructing the SSLIOStream. Unconnected sockets will be
wrapped when IOStream.connect is finished.
“””
def __init__(self, *args, **kwargs):
“””Creates an SSLIOStream.
If a dictionary is provided as keyword argument ssl_options,
it will be used as additional keyword arguments to ssl.wrap_socket.
“””
self._ssl_options = kwargs.pop(‘ssl_options’, {})
super(SSLIOStream, self).__init__(*args, **kwargs)
self._ssl_accepting = True
self._handshake_reading = False
self._handshake_writing = False
def reading(self):
return self._handshake_reading or super(SSLIOStream, self).reading()
def writing(self):
return self._handshake_writing or super(SSLIOStream, self).writing()
def _do_ssl_handshake(self):
# Based on code from test_ssl.py in the python stdlib
try:
self._handshake_reading = False
self._handshake_writing = False
self.socket.do_handshake()
except ssl.SSLError, err:
if err.args[0] == ssl.SSL_ERROR_WANT_READ:
self._handshake_reading = True
return
elif err.args[0] == ssl.SSL_ERROR_WANT_WRITE:
self._handshake_writing = True
return
elif err.args[0] in (ssl.SSL_ERROR_EOF,
ssl.SSL_ERROR_ZERO_RETURN):
return self.close()
elif err.args[0] == ssl.SSL_ERROR_SSL:
logging.warning(“SSL Error on %d: %s”, self.socket.fileno(), err)
return self.close()
raise
except socket.error, err:
if err.args[0] == errno.ECONNABORTED:
return self.close()
else:
self._ssl_accepting = False
super(SSLIOStream, self)._handle_connect()
def _handle_read(self):
if self._ssl_accepting:
self._do_ssl_handshake()
return
super(SSLIOStream, self)._handle_read()
def _handle_write(self):
if self._ssl_accepting:
self._do_ssl_handshake()
return
super(SSLIOStream, self)._handle_write()
def _handle_connect(self):
self.socket = ssl.wrap_socket(self.socket,
do_handshake_on_connect=False,
**self._ssl_options)
# Don’t call the superclass’s _handle_connect (which is responsible
# for telling the application that the connection is complete)
# until we’ve completed the SSL handshake (so certificates are
# available, etc).
def _read_from_socket(self):
try:
# SSLSocket objects have both a read() and recv() method,
# while regular sockets only have recv().
# The recv() method blocks (at least in python 2.6) if it is
# called when there is nothing to read, so we have to use
# read() instead.
chunk = self.socket.read(self.read_chunk_size)
except ssl.SSLError, e:
# SSLError is a subclass of socket.error, so this except
# block must come first.
if e.args[0] == ssl.SSL_ERROR_WANT_READ:
return None
else:
raise
except socket.error, e:
if e.args[0] in (errno.EWOULDBLOCK, errno.EAGAIN):
return None
else:
raise
if not chunk:
self.close()
return None
return chunk
def _merge_prefix(deque, size):
“””Replace the first entries in a deque of strings with a single
string of up to size bytes.
>>> d = collections.deque([‘abc’, ‘de’, ‘fghi’, ‘j’])
>>> _merge_prefix(d, 5); print d
deque([‘abcde’, ‘fghi’, ‘j’])
Strings will be split as necessary to reach the desired size.
>>> _merge_prefix(d, 7); print d
deque([‘abcdefg’, ‘hi’, ‘j’])
>>> _merge_prefix(d, 3); print d
deque([‘abc’, ‘defg’, ‘hi’, ‘j’])
>>> _merge_prefix(d, 100); print d
deque([‘abcdefghij’])
“””
prefix = []
remaining = size
while deque and remaining > 0:
chunk = deque.popleft()
if len(chunk) > remaining:
deque.appendleft(chunk[remaining:])
chunk = chunk[:remaining]
prefix.append(chunk)
remaining -= len(chunk)
deque.appendleft(”.join(prefix))
def doctests():
import doctest
return doctest.DocTestSuite()
copyright
author：bigfish copyright: 许可协议 知识共享署名 - 非商业性使用 4.0 国际许可协议
