class documentation

class HTTPChannel(basic.LineReceiver, policies.TimeoutMixin): (source)

Known subclasses: twisted.web.proxy.Proxy, twisted.web.proxy.ReverseProxy

Implements interfaces: twisted.internet.interfaces.IConsumer, twisted.internet.interfaces.IPushProducer, twisted.internet.interfaces.ITransport

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A receiver for HTTP requests.

The HTTPChannel provides interfaces.ITransport and interfaces.IConsumer to the Request objects it creates. It also implements interfaces.IPushProducer to self.transport, allowing the transport to pause it.

Method __init__ Undocumented
Method allContentReceived Undocumented
Method allHeadersReceived Undocumented
Method checkPersistence Check if the channel should close or not.
Method connectionLost Called when the connection is shut down.
Method connectionMade Called when a connection is made.
Method dataReceived Data was received from the network. Process it.
Method forceAbortClient No summary
Method getHost Get the local address of this connection.
Method getPeer Get the remote address of this connection.
Method headerReceived Do pre-processing (for content-length) and store this header away. Enforce the per-request header limit.
Method isSecure Return True if this channel is using a secure transport.
Method lineReceived Called for each line from request until the end of headers when it enters binary mode.
Method loseConnection Closes the connection. Will write any data that is pending to be sent on the network, but if this response has not yet been written to the network will not write anything.
Method pauseProducing Pause producing data.
Method rawDataReceived Override this for when raw data is received.
Method registerProducer Register to receive data from a producer.
Method requestDone Called by first request in queue when it is done.
Method resumeProducing Resume producing data.
Method stopProducing Stop producing data.
Method timeoutConnection Called when the connection times out.
Method unregisterProducer Stop consuming data from a producer, without disconnecting.
Method write Called by Request objects to write response data.
Method writeHeaders Called by Request objects to write a complete set of HTTP headers to a transport.
Method writeSequence Write a list of strings to the HTTP response.
Instance Variable abortTimeout The number of seconds to wait after we attempt to shut the transport down cleanly to give up and forcibly terminate it. This is only used when we time a connection out, to prevent errors causing the FD to get leaked. If this is None, we will wait forever.
Instance Variable length Undocumented
Instance Variable MAX_LENGTH Maximum length for initial request line and each line from the header.
Instance Variable maxHeaders Maximum number of headers allowed per request.
Instance Variable persistent Undocumented
Instance Variable requests Undocumented
Instance Variable totalHeadersSize Maximum bytes for request line plus all headers from the request.
Method _finishRequestBody Undocumented
Method _maybeChooseTransferDecoder If the provided header is content-length or transfer-encoding, choose the appropriate decoder if any.
Method _respondToBadRequestAndDisconnect This is a quick and dirty way of responding to bad requests.
Method _send100Continue Sends a 100 Continue response, used to signal to clients that further processing will be performed.
Class Variable __content Undocumented
Class Variable _log Undocumented
Instance Variable __first_line Undocumented
Instance Variable __header Undocumented
Instance Variable _abortingCall The twisted.internet.base.DelayedCall that will be used to forcibly close the transport if it doesn't close cleanly.
Instance Variable _command Undocumented
Instance Variable _dataBuffer Any data that has been received from the connection while processing an outstanding request.
Instance Variable _handlingRequest Whether a request is currently being processed.
Instance Variable _networkProducer Either the transport, if it provides interfaces.IPushProducer, or a null implementation of interfaces.IPushProducer. Used to attempt to prevent the transport from producing excess data when we're responding to a request.
Instance Variable _optimisticEagerReadSize When a resource takes a long time to answer a request (via twisted.web.server.NOT_DONE_YET, hopefully one day by a Deferred), we would like to be able to let that resource know about the underlying transport disappearing as promptly as possible, via Request.notifyFinish, and therefore via self.requests[...].connectionLost() on this HTTPChannel.
Instance Variable _path Undocumented
Instance Variable _receivedHeaderCount Undocumented
Instance Variable _receivedHeaderSize Bytes received so far for the header.
Instance Variable _requestProducer If the Request object or anything it calls registers itself as an interfaces.IProducer, it will be stored here. This is used to create a producing pipeline: pause/resume producing methods will be propagated from the transport, through the HTTPChannel instance, to the c{_requestProducer}.
Instance Variable _requestProducerStreaming A boolean that tracks whether the producer on the Request side of this channel has registered itself as a interfaces.IPushProducer or an interfaces.IPullProducer.
Instance Variable _savedTimeOut Undocumented
Instance Variable _transferDecoder None or a decoder instance if the request body uses the chunked Transfer-Encoding.
Instance Variable _version Undocumented
Instance Variable _waitingForTransport A boolean that tracks whether the transport has asked us to stop producing. This is used to keep track of what we're waiting for: if the transport has asked us to stop producing then we don't want to unpause the transport until it asks us to produce again.

Inherited from LineReceiver:

Method clearLineBuffer Clear buffered data.
Method lineLengthExceeded Called when the maximum line length has been reached. Override if it needs to be dealt with in some special way.
Method sendLine Sends a line to the other end of the connection.
Method setLineMode Sets the line-mode of this receiver.
Method setRawMode Sets the raw mode of this receiver. Further data received will be sent to rawDataReceived rather than lineReceived.
Class Variable delimiter The line-ending delimiter to use. By default this is b'\r\n'.
Instance Variable line_mode Undocumented
Instance Variable _buffer Undocumented
Instance Variable _busyReceiving Undocumented

Inherited from Protocol (via LineReceiver):

Method logPrefix Return a prefix matching the class name, to identify log messages related to this protocol instance.
Class Variable factory Undocumented

Inherited from BaseProtocol (via LineReceiver, Protocol):

Method makeConnection Make a connection to a transport and a server.
Instance Variable connected Undocumented
Instance Variable transport Undocumented

Inherited from _PauseableMixin (via LineReceiver):

Instance Variable paused Undocumented

Inherited from TimeoutMixin:

Method callLater Wrapper around reactor.callLater for test purpose.
Method resetTimeout Reset the timeout count down.
Method setTimeout Change the timeout period
Instance Variable timeOut The number of seconds after which to timeout the connection.
Method __timedOut Undocumented
Instance Variable __timeoutCall Undocumented
def __init__(self): (source)

Undocumented

def allContentReceived(self): (source)

Undocumented

def allHeadersReceived(self): (source)

Undocumented

def checkPersistence(self, request, version): (source)
Check if the channel should close or not.
Parameters
requestThe request most recently received over this channel against which checks will be made to determine if this connection can remain open after a matching response is returned.
version:bytesThe version of the request.
Returns
boolA flag which, if True, indicates that this connection may remain open to receive another request; if False, the connection must be closed in order to indicate the completion of the response to request.
def connectionLost(self, reason): (source)

Called when the connection is shut down.

Clear any circular references here, and any external references to this Protocol. The connection has been closed.

Parameters
reason:twisted.python.failure.FailureUndocumented
def connectionMade(self): (source)

Called when a connection is made.

This may be considered the initializer of the protocol, because it is called when the connection is completed. For clients, this is called once the connection to the server has been established; for servers, this is called after an accept() call stops blocking and a socket has been received. If you need to send any greeting or initial message, do it here.

def dataReceived(self, data): (source)
Data was received from the network. Process it.
def forceAbortClient(self): (source)
Called if abortTimeout seconds have passed since the timeout fired, and the connection still hasn't gone away. This can really only happen on extremely bad connections or when clients are maliciously attempting to keep connections open.
def getHost(self): (source)
Get the local address of this connection.
Returns
An IAddress provider.
def getPeer(self): (source)
Get the remote address of this connection.
Returns
An IAddress provider.
def headerReceived(self, line): (source)
Do pre-processing (for content-length) and store this header away. Enforce the per-request header limit.
Parameters
line:bytesA line from the header section of a request, excluding the line delimiter.
Returns
boolA flag indicating whether the header was valid.
def isSecure(self): (source)

Return True if this channel is using a secure transport.

Normally this method returns True if this instance is using a transport that implements interfaces.ISSLTransport.

Returns
boolTrue if this request is secure
def lineReceived(self, line): (source)
Called for each line from request until the end of headers when it enters binary mode.
def loseConnection(self): (source)
Closes the connection. Will write any data that is pending to be sent on the network, but if this response has not yet been written to the network will not write anything.
Returns
None
def pauseProducing(self): (source)

Pause producing data.

This will be called by the transport when the send buffers have been filled up. We want to simultaneously pause the producing Request object and also pause our transport.

The logic behind pausing the transport is specifically to avoid issues like https://twistedmatrix.com/trac/ticket/8868. In this case, our inability to send does not prevent us handling more requests, which means we increasingly queue up more responses in our send buffer without end. The easiest way to handle this is to ensure that if we are unable to send our responses, we will not read further data from the connection until the client pulls some data out. This is a bit of a blunt instrument, but it's ok.

Note that this potentially interacts with timeout handling in a positive way. Once the transport is paused the client may run into a timeout which will cause us to tear the connection down. That's a good thing!

def rawDataReceived(self, data): (source)
Override this for when raw data is received.
def registerProducer(self, producer, streaming): (source)

Register to receive data from a producer.

This sets self to be a consumer for a producer. When this object runs out of data (as when a send(2) call on a socket succeeds in moving the last data from a userspace buffer into a kernelspace buffer), it will ask the producer to resumeProducing().

For IPullProducer providers, resumeProducing will be called once each time data is required.

For IPushProducer providers, pauseProducing will be called whenever the write buffer fills up and resumeProducing will only be called when it empties.

Parameters
producer:IProducer providerThe IProducer that will be producing data.
streaming:boolTrue if producer provides IPushProducer, False if producer provides IPullProducer.
Returns
None
Raises
RuntimeErrorIf a producer is already registered.
def requestDone(self, request): (source)
Called by first request in queue when it is done.
def resumeProducing(self): (source)

Resume producing data.

This will be called by the transport when the send buffer has dropped enough to actually send more data. When this happens we can unpause any outstanding Request producers we have, and also unpause our transport.

def stopProducing(self): (source)

Stop producing data.

The HTTPChannel doesn't *actually* implement this, beacuse the assumption is that it will only be called just before loseConnection is called. There's nothing sensible we can do other than call loseConnection anyway.

def timeoutConnection(self): (source)

Called when the connection times out.

Override to define behavior other than dropping the connection.

def unregisterProducer(self): (source)
Stop consuming data from a producer, without disconnecting.
Returns
None
def write(self, data): (source)
Called by Request objects to write response data.
Parameters
data:bytesThe data chunk to write to the stream.
Returns
None
def writeHeaders(self, version, code, reason, headers): (source)
Called by Request objects to write a complete set of HTTP headers to a transport.
Parameters
version:bytesThe HTTP version in use.
code:bytesThe HTTP status code to write.
reason:bytesThe HTTP reason phrase to write.
headers:twisted.web.http_headers.HeadersThe headers to write to the transport.
def writeSequence(self, iovec): (source)
Write a list of strings to the HTTP response.
Parameters
iovec:list of bytesA list of byte strings to write to the stream.
Returns
None
abortTimeout: int = (source)
The number of seconds to wait after we attempt to shut the transport down cleanly to give up and forcibly terminate it. This is only used when we time a connection out, to prevent errors causing the FD to get leaked. If this is None, we will wait forever.
length: int = (source)

Undocumented

MAX_LENGTH = (source)
Maximum length for initial request line and each line from the header.
maxHeaders: int = (source)
Maximum number of headers allowed per request.
persistent = (source)

Undocumented

requests: list = (source)

Undocumented

totalHeadersSize: int = (source)
Maximum bytes for request line plus all headers from the request.
def _finishRequestBody(self, data): (source)

Undocumented

def _maybeChooseTransferDecoder(self, header, data): (source)

If the provided header is content-length or transfer-encoding, choose the appropriate decoder if any.

Returns True if the request can proceed and False if not.

def _respondToBadRequestAndDisconnect(self): (source)

This is a quick and dirty way of responding to bad requests.

As described by HTTP standard we should be patient and accept the whole request from the client before sending a polite bad request response, even in the case when clients send tons of data.

def _send100Continue(self): (source)
Sends a 100 Continue response, used to signal to clients that further processing will be performed.
__content = (source)

Undocumented

_log = (source)

Undocumented

__first_line: int = (source)

Undocumented

__header = (source)

Undocumented

The twisted.internet.base.DelayedCall that will be used to forcibly close the transport if it doesn't close cleanly.
_command = (source)

Undocumented

_dataBuffer: list of bytes = (source)
Any data that has been received from the connection while processing an outstanding request.
_handlingRequest: bool = (source)
Whether a request is currently being processed.
Either the transport, if it provides interfaces.IPushProducer, or a null implementation of interfaces.IPushProducer. Used to attempt to prevent the transport from producing excess data when we're responding to a request.
_optimisticEagerReadSize: int = (source)

When a resource takes a long time to answer a request (via twisted.web.server.NOT_DONE_YET, hopefully one day by a Deferred), we would like to be able to let that resource know about the underlying transport disappearing as promptly as possible, via Request.notifyFinish, and therefore via self.requests[...].connectionLost() on this HTTPChannel.

However, in order to simplify application logic, we implement head-of-line blocking, and do not relay pipelined requests to the application until the previous request has been answered. This means that said application cannot dispose of any entity-body that comes in from those subsequent requests, which may be arbitrarily large, and it may need to be buffered in memory.

To implement this tradeoff between prompt notification when possible (in the most frequent case of non-pipelined requests) and correct behavior when not (say, if a client sends a very long-running GET request followed by a PUT request with a very large body) we will continue reading pipelined requests into self._dataBuffer up to a given limit.

_optimisticEagerReadSize is the number of bytes we will accept from the client and buffer before pausing the transport.

This behavior has been in place since Twisted 17.9.0 .

_path = (source)

Undocumented

_receivedHeaderCount: int = (source)

Undocumented

_receivedHeaderSize: int = (source)
Bytes received so far for the header.

If the Request object or anything it calls registers itself as an interfaces.IProducer, it will be stored here. This is used to create a producing pipeline: pause/resume producing methods will be propagated from the transport, through the HTTPChannel instance, to the c{_requestProducer}.

The reason we proxy through the producing methods rather than the old behaviour (where we literally just set the Request object as the producer on the transport) is because we want to be able to exert backpressure on the client to prevent it from sending in arbitrarily many requests without ever reading responses. Essentially, if the client never reads our responses we will eventually stop reading its requests.

_requestProducerStreaming: bool or None = (source)
A boolean that tracks whether the producer on the Request side of this channel has registered itself as a interfaces.IPushProducer or an interfaces.IPullProducer.
_savedTimeOut = (source)

Undocumented

None or a decoder instance if the request body uses the chunked Transfer-Encoding.
_version = (source)

Undocumented

_waitingForTransport: bool = (source)
A boolean that tracks whether the transport has asked us to stop producing. This is used to keep track of what we're waiting for: if the transport has asked us to stop producing then we don't want to unpause the transport until it asks us to produce again.