Twisted Example Client: Post RequestsΒΆ
This example is a basic HTTP/2 client written for the Twisted asynchronous networking framework.
This client is fairly simple: it makes a hard-coded POST request to nghttp2.org/httpbin/post and prints out the response data, sending a file that is provided on the command line or the script itself. Its purpose is to demonstrate how to write a HTTP/2 client implementation that handles flow control.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 | # -*- coding: utf-8 -*- """ post_request.py ~~~~~~~~~~~~~~~ A short example that demonstrates a client that makes POST requests to certain websites. This example is intended to demonstrate how to handle uploading request bodies. In this instance, a file will be uploaded. In order to handle arbitrary files, this example also demonstrates how to obey HTTP/2 flow control rules. Takes one command-line argument: a path to a file in the filesystem to upload. If none is present, uploads this file. """ from __future__ import print_function import mimetypes import os import sys from twisted.internet import reactor, defer from twisted.internet.endpoints import connectProtocol, SSL4ClientEndpoint from twisted.internet.protocol import Protocol from twisted.internet.ssl import optionsForClientTLS from h2.connection import H2Connection from h2.events import ( ResponseReceived, DataReceived, StreamEnded, StreamReset, WindowUpdated, SettingsAcknowledged, ) AUTHORITY = u'nghttp2.org' PATH = '/httpbin/post' class H2Protocol(Protocol): def __init__(self, file_path): self.conn = H2Connection() self.known_proto = None self.request_made = False self.request_complete = False self.file_path = file_path self.flow_control_deferred = None self.fileobj = None self.file_size = None def connectionMade(self): """ Called by Twisted when the TCP connection is established. We can start sending some data now: we should open with the connection preamble. """ self.conn.initiate_connection() self.transport.write(self.conn.data_to_send()) def dataReceived(self, data): """ Called by Twisted when data is received on the connection. We need to check a few things here. Firstly, we want to validate that we actually negotiated HTTP/2: if we didn't, we shouldn't proceed! Then, we want to pass the data to the protocol stack and check what events occurred. """ if not self.known_proto: self.known_proto = self.transport.negotiatedProtocol assert self.known_proto == b'h2' events = self.conn.receive_data(data) for event in events: if isinstance(event, ResponseReceived): self.handleResponse(event.headers) elif isinstance(event, DataReceived): self.handleData(event.data) elif isinstance(event, StreamEnded): self.endStream() elif isinstance(event, SettingsAcknowledged): self.settingsAcked(event) elif isinstance(event, StreamReset): reactor.stop() raise RuntimeError("Stream reset: %d" % event.error_code) elif isinstance(event, WindowUpdated): self.windowUpdated(event) data = self.conn.data_to_send() if data: self.transport.write(data) def settingsAcked(self, event): """ Called when the remote party ACKs our settings. We send a SETTINGS frame as part of the preamble, so if we want to be very polite we can wait until the ACK for that frame comes before we start sending our request. """ if not self.request_made: self.sendRequest() def handleResponse(self, response_headers): """ Handle the response by printing the response headers. """ for name, value in response_headers: print("%s: %s" % (name.decode('utf-8'), value.decode('utf-8'))) print("") def handleData(self, data): """ We handle data that's received by just printing it. """ print(data, end='') def endStream(self): """ We call this when the stream is cleanly ended by the remote peer. That means that the response is complete. Because this code only makes a single HTTP/2 request, once we receive the complete response we can safely tear the connection down and stop the reactor. We do that as cleanly as possible. """ self.request_complete = True self.conn.close_connection() self.transport.write(self.conn.data_to_send()) self.transport.loseConnection() def windowUpdated(self, event): """ We call this when the flow control window for the connection or the stream has been widened. If there's a flow control deferred present (that is, if we're blocked behind the flow control), we fire it. Otherwise, we do nothing. """ if self.flow_control_deferred is None: return # Make sure we remove the flow control deferred to avoid firing it # more than once. flow_control_deferred = self.flow_control_deferred self.flow_control_deferred = None flow_control_deferred.callback(None) def connectionLost(self, reason=None): """ Called by Twisted when the connection is gone. Regardless of whether it was clean or not, we want to stop the reactor. """ if self.fileobj is not None: self.fileobj.close() if reactor.running: reactor.stop() def sendRequest(self): """ Send the POST request. A POST request is made up of one headers frame, and then 0+ data frames. This method begins by sending the headers, and then starts a series of calls to send data. """ # First, we need to work out how large the file is. self.file_size = os.stat(self.file_path).st_size # Next, we want to guess a content-type and content-encoding. content_type, content_encoding = mimetypes.guess_type(self.file_path) # Now we can build a header block. request_headers = [ (':method', 'POST'), (':authority', AUTHORITY), (':scheme', 'https'), (':path', PATH), ('content-length', str(self.file_size)), ] if content_type is not None: request_headers.append(('content-type', content_type)) if content_encoding is not None: request_headers.append(('content-encoding', content_encoding)) self.conn.send_headers(1, request_headers) self.request_made = True # We can now open the file. self.fileobj = open(self.file_path, 'rb') # We now need to send all the relevant data. We do this by checking # what the acceptable amount of data is to send, and sending it. If we # find ourselves blocked behind flow control, we then place a deferred # and wait until that deferred fires. self.sendFileData() def sendFileData(self): """ Send some file data on the connection. """ # Firstly, check what the flow control window is for stream 1. window_size = self.conn.local_flow_control_window(stream_id=1) # Next, check what the maximum frame size is. max_frame_size = self.conn.max_outbound_frame_size # We will send no more than the window size or the remaining file size # of data in this call, whichever is smaller. bytes_to_send = min(window_size, self.file_size) # We now need to send a number of data frames. while bytes_to_send > 0: chunk_size = min(bytes_to_send, max_frame_size) data_chunk = self.fileobj.read(chunk_size) self.conn.send_data(stream_id=1, data=data_chunk) bytes_to_send -= chunk_size self.file_size -= chunk_size # We've prepared a whole chunk of data to send. If the file is fully # sent, we also want to end the stream: we're done here. if self.file_size == 0: self.conn.end_stream(stream_id=1) else: # We've still got data left to send but the window is closed. Save # a Deferred that will call us when the window gets opened. self.flow_control_deferred = defer.Deferred() self.flow_control_deferred.addCallback(self.sendFileData) self.transport.write(self.conn.data_to_send()) try: filename = sys.argv[1] except IndexError: filename = __file__ options = optionsForClientTLS( hostname=AUTHORITY, acceptableProtocols=[b'h2'], ) connectProtocol( SSL4ClientEndpoint(reactor, AUTHORITY, 443, options), H2Protocol(filename) ) reactor.run() |