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/ connection.py
"""AMQP Connections"""
# Copyright (C) 2007-2008 Barry Pederson <bp@barryp.org>
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301
from __future__ import absolute_import
import logging
import socket
from array import array
try:
from ssl import SSLError
except ImportError:
class SSLError(Exception): # noqa
pass
from . import __version__
from .abstract_channel import AbstractChannel
from .channel import Channel
from .exceptions import (
AMQPNotImplementedError, ChannelError, ResourceError,
ConnectionForced, ConnectionError, error_for_code,
RecoverableConnectionError, RecoverableChannelError,
)
from .five import items, range, values, monotonic
from .method_framing import MethodReader, MethodWriter
from .serialization import AMQPWriter
from .transport import create_transport
HAS_MSG_PEEK = hasattr(socket, 'MSG_PEEK')
START_DEBUG_FMT = """
Start from server, version: %d.%d, properties: %s, mechanisms: %s, locales: %s
""".strip()
__all__ = ['Connection']
#
# Client property info that gets sent to the server on connection startup
#
LIBRARY_PROPERTIES = {
'product': 'py-amqp',
'product_version': __version__,
'capabilities': {},
}
AMQP_LOGGER = logging.getLogger('amqp')
class Connection(AbstractChannel):
"""The connection class provides methods for a client to establish a
network connection to a server, and for both peers to operate the
connection thereafter.
GRAMMAR::
connection = open-connection *use-connection close-connection
open-connection = C:protocol-header
S:START C:START-OK
*challenge
S:TUNE C:TUNE-OK
C:OPEN S:OPEN-OK
challenge = S:SECURE C:SECURE-OK
use-connection = *channel
close-connection = C:CLOSE S:CLOSE-OK
/ S:CLOSE C:CLOSE-OK
"""
Channel = Channel
#: Final heartbeat interval value (in float seconds) after negotiation
heartbeat = None
#: Original heartbeat interval value proposed by client.
client_heartbeat = None
#: Original heartbeat interval proposed by server.
server_heartbeat = None
#: Time of last heartbeat sent (in monotonic time, if available).
last_heartbeat_sent = 0
#: Time of last heartbeat received (in monotonic time, if available).
last_heartbeat_received = 0
#: Number of bytes sent to socket at the last heartbeat check.
prev_sent = None
#: Number of bytes received from socket at the last heartbeat check.
prev_recv = None
def __init__(self, host='localhost', userid='guest', password='guest',
login_method='AMQPLAIN', login_response=None,
virtual_host='/', locale='en_US', client_properties=None,
ssl=False, connect_timeout=None, channel_max=None,
frame_max=None, heartbeat=0, on_blocked=None,
on_unblocked=None, confirm_publish=False, **kwargs):
"""Create a connection to the specified host, which should be
a 'host[:port]', such as 'localhost', or '1.2.3.4:5672'
(defaults to 'localhost', if a port is not specified then
5672 is used)
If login_response is not specified, one is built up for you from
userid and password if they are present.
The 'ssl' parameter may be simply True/False, or for Python >= 2.6
a dictionary of options to pass to ssl.wrap_socket() such as
requiring certain certificates.
"""
channel_max = channel_max or 65535
frame_max = frame_max or 131072
if (login_response is None) \
and (userid is not None) \
and (password is not None):
login_response = AMQPWriter()
login_response.write_table({'LOGIN': userid, 'PASSWORD': password})
# Skip the length at the beginning
login_response = login_response.getvalue()[4:]
d = dict(LIBRARY_PROPERTIES, **client_properties or {})
self._method_override = {(60, 50): self._dispatch_basic_return}
self.channels = {}
# The connection object itself is treated as channel 0
super(Connection, self).__init__(self, 0)
self.transport = None
# Properties set in the Tune method
self.channel_max = channel_max
self.frame_max = frame_max
self.client_heartbeat = heartbeat
self.confirm_publish = confirm_publish
# Callbacks
self.on_blocked = on_blocked
self.on_unblocked = on_unblocked
self._avail_channel_ids = array('H', range(self.channel_max, 0, -1))
# Properties set in the Start method
self.version_major = 0
self.version_minor = 0
self.server_properties = {}
self.mechanisms = []
self.locales = []
# Let the transport.py module setup the actual
# socket connection to the broker.
#
self.transport = self.Transport(host, connect_timeout, ssl)
self.method_reader = MethodReader(self.transport)
self.method_writer = MethodWriter(self.transport, self.frame_max)
self.wait(allowed_methods=[
(10, 10), # start
])
self._x_start_ok(d, login_method, login_response, locale)
self._wait_tune_ok = True
while self._wait_tune_ok:
self.wait(allowed_methods=[
(10, 20), # secure
(10, 30), # tune
])
return self._x_open(virtual_host)
def Transport(self, host, connect_timeout, ssl=False):
return create_transport(host, connect_timeout, ssl)
@property
def connected(self):
return self.transport and self.transport.connected
def _do_close(self):
try:
self.transport.close()
temp_list = [x for x in values(self.channels) if x is not self]
for ch in temp_list:
ch._do_close()
except socket.error:
pass # connection already closed on the other end
finally:
self.transport = self.connection = self.channels = None
def _get_free_channel_id(self):
try:
return self._avail_channel_ids.pop()
except IndexError:
raise ResourceError(
'No free channel ids, current={0}, channel_max={1}'.format(
len(self.channels), self.channel_max), (20, 10))
def _claim_channel_id(self, channel_id):
try:
return self._avail_channel_ids.remove(channel_id)
except ValueError:
raise ConnectionError(
'Channel %r already open' % (channel_id, ))
def _wait_method(self, channel_id, allowed_methods, timeout=None):
"""Wait for a method from the server destined for
a particular channel."""
#
# Check the channel's deferred methods
#
method_queue = self.channels[channel_id].method_queue
for queued_method in method_queue:
method_sig = queued_method[0]
if (allowed_methods is None) \
or (method_sig in allowed_methods) \
or (method_sig == (20, 40)):
method_queue.remove(queued_method)
return queued_method
#
# Nothing queued, need to wait for a method from the peer
#
read_timeout = self.read_timeout
wait = self.wait
while 1:
channel, method_sig, args, content = read_timeout(timeout)
if channel == channel_id and (
allowed_methods is None or
method_sig in allowed_methods or
method_sig == (20, 40)):
return method_sig, args, content
#
# Certain methods like basic_return should be dispatched
# immediately rather than being queued, even if they're not
# one of the 'allowed_methods' we're looking for.
#
if channel and method_sig in self.Channel._IMMEDIATE_METHODS:
self.channels[channel].dispatch_method(
method_sig, args, content,
)
continue
#
# Not the channel and/or method we were looking for. Queue
# this method for later
#
self.channels[channel].method_queue.append(
(method_sig, args, content),
)
#
# If we just queued up a method for channel 0 (the Connection
# itself) it's probably a close method in reaction to some
# error, so deal with it right away.
#
if not channel:
wait()
def channel(self, channel_id=None):
"""Fetch a Channel object identified by the numeric channel_id, or
create that object if it doesn't already exist."""
try:
return self.channels[channel_id]
except KeyError:
return self.Channel(self, channel_id)
def is_alive(self):
if HAS_MSG_PEEK:
sock = self.sock
prev = sock.gettimeout()
sock.settimeout(0.0001)
try:
sock.recv(1, socket.MSG_PEEK)
except socket.timeout:
pass
except socket.error:
return False
finally:
sock.settimeout(prev)
return True
def drain_events(self, timeout=None):
"""Wait for an event on a channel."""
chanmap = self.channels
chanid, method_sig, args, content = self._wait_multiple(
chanmap, None, timeout=timeout,
)
channel = chanmap[chanid]
if (content and
channel.auto_decode and
hasattr(content, 'content_encoding')):
try:
content.body = content.body.decode(content.content_encoding)
except Exception:
pass
amqp_method = (self._method_override.get(method_sig) or
channel._METHOD_MAP.get(method_sig, None))
if amqp_method is None:
raise AMQPNotImplementedError(
'Unknown AMQP method {0!r}'.format(method_sig))
if content is None:
return amqp_method(channel, args)
else:
return amqp_method(channel, args, content)
def read_timeout(self, timeout=None):
if timeout is None:
return self.method_reader.read_method()
sock = self.sock
prev = sock.gettimeout()
if prev != timeout:
sock.settimeout(timeout)
try:
try:
return self.method_reader.read_method()
except SSLError as exc:
# http://bugs.python.org/issue10272
if 'timed out' in str(exc):
raise socket.timeout()
# Non-blocking SSL sockets can throw SSLError
if 'The operation did not complete' in str(exc):
raise socket.timeout()
raise
finally:
if prev != timeout:
sock.settimeout(prev)
def _wait_multiple(self, channels, allowed_methods, timeout=None):
for channel_id, channel in items(channels):
method_queue = channel.method_queue
for queued_method in method_queue:
method_sig = queued_method[0]
if (allowed_methods is None or
method_sig in allowed_methods or
method_sig == (20, 40)):
method_queue.remove(queued_method)
method_sig, args, content = queued_method
return channel_id, method_sig, args, content
# Nothing queued, need to wait for a method from the peer
read_timeout = self.read_timeout
wait = self.wait
while 1:
channel, method_sig, args, content = read_timeout(timeout)
if channel in channels and (
allowed_methods is None or
method_sig in allowed_methods or
method_sig == (20, 40)):
return channel, method_sig, args, content
# Not the channel and/or method we were looking for. Queue
# this method for later
channels[channel].method_queue.append((method_sig, args, content))
#
# If we just queued up a method for channel 0 (the Connection
# itself) it's probably a close method in reaction to some
# error, so deal with it right away.
#
if channel == 0:
wait()
def _dispatch_basic_return(self, channel, args, msg):
reply_code = args.read_short()
reply_text = args.read_shortstr()
exchange = args.read_shortstr()
routing_key = args.read_shortstr()
exc = error_for_code(reply_code, reply_text, (50, 60), ChannelError)
handlers = channel.events.get('basic_return')
if not handlers:
raise exc
for callback in handlers:
callback(exc, exchange, routing_key, msg)
def close(self, reply_code=0, reply_text='', method_sig=(0, 0)):
"""Request a connection close
This method indicates that the sender wants to close the
connection. This may be due to internal conditions (e.g. a
forced shut-down) or due to an error handling a specific
method, i.e. an exception. When a close is due to an
exception, the sender provides the class and method id of the
method which caused the exception.
RULE:
After sending this method any received method except the
Close-OK method MUST be discarded.
RULE:
The peer sending this method MAY use a counter or timeout
to detect failure of the other peer to respond correctly
with the Close-OK method.
RULE:
When a server receives the Close method from a client it
MUST delete all server-side resources associated with the
client's context. A client CANNOT reconnect to a context
after sending or receiving a Close method.
PARAMETERS:
reply_code: short
The reply code. The AMQ reply codes are defined in AMQ
RFC 011.
reply_text: shortstr
The localised reply text. This text can be logged as an
aid to resolving issues.
class_id: short
failing method class
When the close is provoked by a method exception, this
is the class of the method.
method_id: short
failing method ID
When the close is provoked by a method exception, this
is the ID of the method.
"""
if self.transport is None:
# already closed
return
args = AMQPWriter()
args.write_short(reply_code)
args.write_shortstr(reply_text)
args.write_short(method_sig[0]) # class_id
args.write_short(method_sig[1]) # method_id
self._send_method((10, 50), args)
return self.wait(allowed_methods=[
(10, 50), # Connection.close
(10, 51), # Connection.close_ok
])
def _close(self, args):
"""Request a connection close
This method indicates that the sender wants to close the
connection. This may be due to internal conditions (e.g. a
forced shut-down) or due to an error handling a specific
method, i.e. an exception. When a close is due to an
exception, the sender provides the class and method id of the
method which caused the exception.
RULE:
After sending this method any received method except the
Close-OK method MUST be discarded.
RULE:
The peer sending this method MAY use a counter or timeout
to detect failure of the other peer to respond correctly
with the Close-OK method.
RULE:
When a server receives the Close method from a client it
MUST delete all server-side resources associated with the
client's context. A client CANNOT reconnect to a context
after sending or receiving a Close method.
PARAMETERS:
reply_code: short
The reply code. The AMQ reply codes are defined in AMQ
RFC 011.
reply_text: shortstr
The localised reply text. This text can be logged as an
aid to resolving issues.
class_id: short
failing method class
When the close is provoked by a method exception, this
is the class of the method.
method_id: short
failing method ID
When the close is provoked by a method exception, this
is the ID of the method.
"""
reply_code = args.read_short()
reply_text = args.read_shortstr()
class_id = args.read_short()
method_id = args.read_short()
self._x_close_ok()
raise error_for_code(reply_code, reply_text,
(class_id, method_id), ConnectionError)
def _blocked(self, args):
"""RabbitMQ Extension."""
reason = args.read_shortstr()
if self.on_blocked:
return self.on_blocked(reason)
def _unblocked(self, *args):
if self.on_unblocked:
return self.on_unblocked()
def _x_close_ok(self):
"""Confirm a connection close
This method confirms a Connection.Close method and tells the
recipient that it is safe to release resources for the
connection and close the socket.
RULE:
A peer that detects a socket closure without having
received a Close-Ok handshake method SHOULD log the error.
"""
self._send_method((10, 51))
self._do_close()
def _close_ok(self, args):
"""Confirm a connection close
This method confirms a Connection.Close method and tells the
recipient that it is safe to release resources for the
connection and close the socket.
RULE:
A peer that detects a socket closure without having
received a Close-Ok handshake method SHOULD log the error.
"""
self._do_close()
def _x_open(self, virtual_host, capabilities=''):
"""Open connection to virtual host
This method opens a connection to a virtual host, which is a
collection of resources, and acts to separate multiple
application domains within a server.
RULE:
The client MUST open the context before doing any work on
the connection.
PARAMETERS:
virtual_host: shortstr
virtual host name
The name of the virtual host to work with.
RULE:
If the server supports multiple virtual hosts, it
MUST enforce a full separation of exchanges,
queues, and all associated entities per virtual
host. An application, connected to a specific
virtual host, MUST NOT be able to access resources
of another virtual host.
RULE:
The server SHOULD verify that the client has
permission to access the specified virtual host.
RULE:
The server MAY configure arbitrary limits per
virtual host, such as the number of each type of
entity that may be used, per connection and/or in
total.
capabilities: shortstr
required capabilities
The client may specify a number of capability names,
delimited by spaces. The server can use this string
to how to process the client's connection request.
"""
args = AMQPWriter()
args.write_shortstr(virtual_host)
args.write_shortstr(capabilities)
args.write_bit(False)
self._send_method((10, 40), args)
return self.wait(allowed_methods=[
(10, 41), # Connection.open_ok
])
def _open_ok(self, args):
"""Signal that the connection is ready
This method signals to the client that the connection is ready
for use.
PARAMETERS:
known_hosts: shortstr (deprecated)
"""
AMQP_LOGGER.debug('Open OK!')
def _secure(self, args):
"""Security mechanism challenge
The SASL protocol works by exchanging challenges and responses
until both peers have received sufficient information to
authenticate each other. This method challenges the client to
provide more information.
PARAMETERS:
challenge: longstr
security challenge data
Challenge information, a block of opaque binary data
passed to the security mechanism.
"""
challenge = args.read_longstr() # noqa
def _x_secure_ok(self, response):
"""Security mechanism response
This method attempts to authenticate, passing a block of SASL
data for the security mechanism at the server side.
PARAMETERS:
response: longstr
security response data
A block of opaque data passed to the security
mechanism. The contents of this data are defined by
the SASL security mechanism.
"""
args = AMQPWriter()
args.write_longstr(response)
self._send_method((10, 21), args)
def _start(self, args):
"""Start connection negotiation
This method starts the connection negotiation process by
telling the client the protocol version that the server
proposes, along with a list of security mechanisms which the
client can use for authentication.
RULE:
If the client cannot handle the protocol version suggested
by the server it MUST close the socket connection.
RULE:
The server MUST provide a protocol version that is lower
than or equal to that requested by the client in the
protocol header. If the server cannot support the
specified protocol it MUST NOT send this method, but MUST
close the socket connection.
PARAMETERS:
version_major: octet
protocol major version
The protocol major version that the server agrees to
use, which cannot be higher than the client's major
version.
version_minor: octet
protocol major version
The protocol minor version that the server agrees to
use, which cannot be higher than the client's minor
version.
server_properties: table
server properties
mechanisms: longstr
available security mechanisms
A list of the security mechanisms that the server
supports, delimited by spaces. Currently ASL supports
these mechanisms: PLAIN.
locales: longstr
available message locales
A list of the message locales that the server
supports, delimited by spaces. The locale defines the
language in which the server will send reply texts.
RULE:
All servers MUST support at least the en_US
locale.
"""
self.version_major = args.read_octet()
self.version_minor = args.read_octet()
self.server_properties = args.read_table()
self.mechanisms = args.read_longstr().split(' ')
self.locales = args.read_longstr().split(' ')
AMQP_LOGGER.debug(
START_DEBUG_FMT,
self.version_major, self.version_minor,
self.server_properties, self.mechanisms, self.locales,
)
def _x_start_ok(self, client_properties, mechanism, response, locale):
"""Select security mechanism and locale
This method selects a SASL security mechanism. ASL uses SASL
(RFC2222) to negotiate authentication and encryption.
PARAMETERS:
client_properties: table
client properties
mechanism: shortstr
selected security mechanism
A single security mechanisms selected by the client,
which must be one of those specified by the server.
RULE:
The client SHOULD authenticate using the highest-
level security profile it can handle from the list
provided by the server.
RULE:
The mechanism field MUST contain one of the
security mechanisms proposed by the server in the
Start method. If it doesn't, the server MUST close
the socket.
response: longstr
security response data
A block of opaque data passed to the security
mechanism. The contents of this data are defined by
the SASL security mechanism. For the PLAIN security
mechanism this is defined as a field table holding two
fields, LOGIN and PASSWORD.
locale: shortstr
selected message locale
A single message local selected by the client, which
must be one of those specified by the server.
"""
if self.server_capabilities.get('consumer_cancel_notify'):
if 'capabilities' not in client_properties:
client_properties['capabilities'] = {}
client_properties['capabilities']['consumer_cancel_notify'] = True
if self.server_capabilities.get('connection.blocked'):
if 'capabilities' not in client_properties:
client_properties['capabilities'] = {}
client_properties['capabilities']['connection.blocked'] = True
args = AMQPWriter()
args.write_table(client_properties)
args.write_shortstr(mechanism)
args.write_longstr(response)
args.write_shortstr(locale)
self._send_method((10, 11), args)
def _tune(self, args):
"""Propose connection tuning parameters
This method proposes a set of connection configuration values
to the client. The client can accept and/or adjust these.
PARAMETERS:
channel_max: short
proposed maximum channels
The maximum total number of channels that the server
allows per connection. Zero means that the server does
not impose a fixed limit, but the number of allowed
channels may be limited by available server resources.
frame_max: long
proposed maximum frame size
The largest frame size that the server proposes for
the connection. The client can negotiate a lower
value. Zero means that the server does not impose any
specific limit but may reject very large frames if it
cannot allocate resources for them.
RULE:
Until the frame-max has been negotiated, both
peers MUST accept frames of up to 4096 octets
large. The minimum non-zero value for the frame-
max field is 4096.
heartbeat: short
desired heartbeat delay
The delay, in seconds, of the connection heartbeat
that the server wants. Zero means the server does not
want a heartbeat.
"""
client_heartbeat = self.client_heartbeat or 0
self.channel_max = args.read_short() or self.channel_max
self.frame_max = args.read_long() or self.frame_max
self.method_writer.frame_max = self.frame_max
self.server_heartbeat = args.read_short() or 0
# negotiate the heartbeat interval to the smaller of the
# specified values
if self.server_heartbeat == 0 or client_heartbeat == 0:
self.heartbeat = max(self.server_heartbeat, client_heartbeat)
else:
self.heartbeat = min(self.server_heartbeat, client_heartbeat)
# Ignore server heartbeat if client_heartbeat is disabled
if not self.client_heartbeat:
self.heartbeat = 0
self._x_tune_ok(self.channel_max, self.frame_max, self.heartbeat)
def send_heartbeat(self):
self.transport.write_frame(8, 0, bytes())
def heartbeat_tick(self, rate=2):
"""Send heartbeat packets, if necessary, and fail if none have been
received recently. This should be called frequently, on the order of
once per second.
:keyword rate: Ignored
"""
if not self.heartbeat:
return
# treat actual data exchange in either direction as a heartbeat
sent_now = self.method_writer.bytes_sent
recv_now = self.method_reader.bytes_recv
if self.prev_sent is None or self.prev_sent != sent_now:
self.last_heartbeat_sent = monotonic()
if self.prev_recv is None or self.prev_recv != recv_now:
self.last_heartbeat_received = monotonic()
self.prev_sent, self.prev_recv = sent_now, recv_now
# send a heartbeat if it's time to do so
if monotonic() > self.last_heartbeat_sent + self.heartbeat:
self.send_heartbeat()
self.last_heartbeat_sent = monotonic()
# if we've missed two intervals' heartbeats, fail; this gives the
# server enough time to send heartbeats a little late
if (self.last_heartbeat_received and
self.last_heartbeat_received + 2 *
self.heartbeat < monotonic()):
raise ConnectionForced('Too many heartbeats missed')
def _x_tune_ok(self, channel_max, frame_max, heartbeat):
"""Negotiate connection tuning parameters
This method sends the client's connection tuning parameters to
the server. Certain fields are negotiated, others provide
capability information.
PARAMETERS:
channel_max: short
negotiated maximum channels
The maximum total number of channels that the client
will use per connection. May not be higher than the
value specified by the server.
RULE:
The server MAY ignore the channel-max value or MAY
use it for tuning its resource allocation.
frame_max: long
negotiated maximum frame size
The largest frame size that the client and server will
use for the connection. Zero means that the client
does not impose any specific limit but may reject very
large frames if it cannot allocate resources for them.
Note that the frame-max limit applies principally to
content frames, where large contents can be broken
into frames of arbitrary size.
RULE:
Until the frame-max has been negotiated, both
peers must accept frames of up to 4096 octets
large. The minimum non-zero value for the frame-
max field is 4096.
heartbeat: short
desired heartbeat delay
The delay, in seconds, of the connection heartbeat
that the client wants. Zero means the client does not
want a heartbeat.
"""
args = AMQPWriter()
args.write_short(channel_max)
args.write_long(frame_max)
args.write_short(heartbeat or 0)
self._send_method((10, 31), args)
self._wait_tune_ok = False
@property
def sock(self):
return self.transport.sock
@property
def server_capabilities(self):
return self.server_properties.get('capabilities') or {}
_METHOD_MAP = {
(10, 10): _start,
(10, 20): _secure,
(10, 30): _tune,
(10, 41): _open_ok,
(10, 50): _close,
(10, 51): _close_ok,
(10, 60): _blocked,
(10, 61): _unblocked,
}
_IMMEDIATE_METHODS = []
connection_errors = (
ConnectionError,
socket.error,
IOError,
OSError,
)
channel_errors = (ChannelError, )
recoverable_connection_errors = (
RecoverableConnectionError,
socket.error,
IOError,
OSError,
)
recoverable_channel_errors = (
RecoverableChannelError,
)