source file: /System/Library/Frameworks/Python.framework/Versions/2.3/lib/python2.3/SocketServer.py
file stats: 173 lines, 71 executed: 41.0% covered
1. """Generic socket server classes. 2. 3. This module tries to capture the various aspects of defining a server: 4. 5. For socket-based servers: 6. 7. - address family: 8. - AF_INET{,6}: IP (Internet Protocol) sockets (default) 9. - AF_UNIX: Unix domain sockets 10. - others, e.g. AF_DECNET are conceivable (see <socket.h> 11. - socket type: 12. - SOCK_STREAM (reliable stream, e.g. TCP) 13. - SOCK_DGRAM (datagrams, e.g. UDP) 14. 15. For request-based servers (including socket-based): 16. 17. - client address verification before further looking at the request 18. (This is actually a hook for any processing that needs to look 19. at the request before anything else, e.g. logging) 20. - how to handle multiple requests: 21. - synchronous (one request is handled at a time) 22. - forking (each request is handled by a new process) 23. - threading (each request is handled by a new thread) 24. 25. The classes in this module favor the server type that is simplest to 26. write: a synchronous TCP/IP server. This is bad class design, but 27. save some typing. (There's also the issue that a deep class hierarchy 28. slows down method lookups.) 29. 30. There are five classes in an inheritance diagram, four of which represent 31. synchronous servers of four types: 32. 33. +------------+ 34. | BaseServer | 35. +------------+ 36. | 37. v 38. +-----------+ +------------------+ 39. | TCPServer |------->| UnixStreamServer | 40. +-----------+ +------------------+ 41. | 42. v 43. +-----------+ +--------------------+ 44. | UDPServer |------->| UnixDatagramServer | 45. +-----------+ +--------------------+ 46. 47. Note that UnixDatagramServer derives from UDPServer, not from 48. UnixStreamServer -- the only difference between an IP and a Unix 49. stream server is the address family, which is simply repeated in both 50. unix server classes. 51. 52. Forking and threading versions of each type of server can be created 53. using the ForkingServer and ThreadingServer mix-in classes. For 54. instance, a threading UDP server class is created as follows: 55. 56. class ThreadingUDPServer(ThreadingMixIn, UDPServer): pass 57. 58. The Mix-in class must come first, since it overrides a method defined 59. in UDPServer! Setting the various member variables also changes 60. the behavior of the underlying server mechanism. 61. 62. To implement a service, you must derive a class from 63. BaseRequestHandler and redefine its handle() method. You can then run 64. various versions of the service by combining one of the server classes 65. with your request handler class. 66. 67. The request handler class must be different for datagram or stream 68. services. This can be hidden by using the mix-in request handler 69. classes StreamRequestHandler or DatagramRequestHandler. 70. 71. Of course, you still have to use your head! 72. 73. For instance, it makes no sense to use a forking server if the service 74. contains state in memory that can be modified by requests (since the 75. modifications in the child process would never reach the initial state 76. kept in the parent process and passed to each child). In this case, 77. you can use a threading server, but you will probably have to use 78. locks to avoid two requests that come in nearly simultaneous to apply 79. conflicting changes to the server state. 80. 81. On the other hand, if you are building e.g. an HTTP server, where all 82. data is stored externally (e.g. in the file system), a synchronous 83. class will essentially render the service "deaf" while one request is 84. being handled -- which may be for a very long time if a client is slow 85. to reqd all the data it has requested. Here a threading or forking 86. server is appropriate. 87. 88. In some cases, it may be appropriate to process part of a request 89. synchronously, but to finish processing in a forked child depending on 90. the request data. This can be implemented by using a synchronous 91. server and doing an explicit fork in the request handler class 92. handle() method. 93. 94. Another approach to handling multiple simultaneous requests in an 95. environment that supports neither threads nor fork (or where these are 96. too expensive or inappropriate for the service) is to maintain an 97. explicit table of partially finished requests and to use select() to 98. decide which request to work on next (or whether to handle a new 99. incoming request). This is particularly important for stream services 100. where each client can potentially be connected for a long time (if 101. threads or subprocesses cannot be used). 102. 103. Future work: 104. - Standard classes for Sun RPC (which uses either UDP or TCP) 105. - Standard mix-in classes to implement various authentication 106. and encryption schemes 107. - Standard framework for select-based multiplexing 108. 109. XXX Open problems: 110. - What to do with out-of-band data? 111. 112. BaseServer: 113. - split generic "request" functionality out into BaseServer class. 114. Copyright (C) 2000 Luke Kenneth Casson Leighton <lkcl@samba.org> 115. 116. example: read entries from a SQL database (requires overriding 117. get_request() to return a table entry from the database). 118. entry is processed by a RequestHandlerClass. 119. 120. """ 121. 122. # Author of the BaseServer patch: Luke Kenneth Casson Leighton 123. 124. # XXX Warning! 125. # There is a test suite for this module, but it cannot be run by the 126. # standard regression test. 127. # To run it manually, run Lib/test/test_socketserver.py. 128. 129. __version__ = "0.4" 130. 131. 132. import socket 133. import sys 134. import os 135. 136. __all__ = ["TCPServer","UDPServer","ForkingUDPServer","ForkingTCPServer", 137. "ThreadingUDPServer","ThreadingTCPServer","BaseRequestHandler", 138. "StreamRequestHandler","DatagramRequestHandler", 139. "ThreadingMixIn", "ForkingMixIn"] 140. if hasattr(socket, "AF_UNIX"): 141. __all__.extend(["UnixStreamServer","UnixDatagramServer", 142. "ThreadingUnixStreamServer", 143. "ThreadingUnixDatagramServer"]) 144. 145. class BaseServer: 146. 147. """Base class for server classes. 148. 149. Methods for the caller: 150. 151. - __init__(server_address, RequestHandlerClass) 152. - serve_forever() 153. - handle_request() # if you do not use serve_forever() 154. - fileno() -> int # for select() 155. 156. Methods that may be overridden: 157. 158. - server_bind() 159. - server_activate() 160. - get_request() -> request, client_address 161. - verify_request(request, client_address) 162. - server_close() 163. - process_request(request, client_address) 164. - close_request(request) 165. - handle_error() 166. 167. Methods for derived classes: 168. 169. - finish_request(request, client_address) 170. 171. Class variables that may be overridden by derived classes or 172. instances: 173. 174. - address_family 175. - socket_type 176. - allow_reuse_address 177. 178. Instance variables: 179. 180. - RequestHandlerClass 181. - socket 182. 183. """ 184. 185. def __init__(self, server_address, RequestHandlerClass): 186. """Constructor. May be extended, do not override.""" 187. self.server_address = server_address 188. self.RequestHandlerClass = RequestHandlerClass 189. 190. def server_activate(self): 191. """Called by constructor to activate the server. 192. 193. May be overridden. 194. 195. """ 196. pass 197. 198. def serve_forever(self): 199. """Handle one request at a time until doomsday.""" 200. while 1: 201. self.handle_request() 202. 203. # The distinction between handling, getting, processing and 204. # finishing a request is fairly arbitrary. Remember: 205. # 206. # - handle_request() is the top-level call. It calls 207. # get_request(), verify_request() and process_request() 208. # - get_request() is different for stream or datagram sockets 209. # - process_request() is the place that may fork a new process 210. # or create a new thread to finish the request 211. # - finish_request() instantiates the request handler class; 212. # this constructor will handle the request all by itself 213. 214. def handle_request(self): 215. """Handle one request, possibly blocking.""" 216. try: 217. request, client_address = self.get_request() 218. except socket.error: 219. return 220. if self.verify_request(request, client_address): 221. try: 222. self.process_request(request, client_address) 223. except: 224. self.handle_error(request, client_address) 225. self.close_request(request) 226. 227. def verify_request(self, request, client_address): 228. """Verify the request. May be overridden. 229. 230. Return True if we should proceed with this request. 231. 232. """ 233. return True 234. 235. def process_request(self, request, client_address): 236. """Call finish_request. 237. 238. Overridden by ForkingMixIn and ThreadingMixIn. 239. 240. """ 241. self.finish_request(request, client_address) 242. self.close_request(request) 243. 244. def server_close(self): 245. """Called to clean-up the server. 246. 247. May be overridden. 248. 249. """ 250. pass 251. 252. def finish_request(self, request, client_address): 253. """Finish one request by instantiating RequestHandlerClass.""" 254. self.RequestHandlerClass(request, client_address, self) 255. 256. def close_request(self, request): 257. """Called to clean up an individual request.""" 258. pass 259. 260. def handle_error(self, request, client_address): 261. """Handle an error gracefully. May be overridden. 262. 263. The default is to print a traceback and continue. 264. 265. """ 266. print '-'*40 267. print 'Exception happened during processing of request from', 268. print client_address 269. import traceback 270. traceback.print_exc() # XXX But this goes to stderr! 271. print '-'*40 272. 273. 274. class TCPServer(BaseServer): 275. 276. """Base class for various socket-based server classes. 277. 278. Defaults to synchronous IP stream (i.e., TCP). 279. 280. Methods for the caller: 281. 282. - __init__(server_address, RequestHandlerClass) 283. - serve_forever() 284. - handle_request() # if you don't use serve_forever() 285. - fileno() -> int # for select() 286. 287. Methods that may be overridden: 288. 289. - server_bind() 290. - server_activate() 291. - get_request() -> request, client_address 292. - verify_request(request, client_address) 293. - process_request(request, client_address) 294. - close_request(request) 295. - handle_error() 296. 297. Methods for derived classes: 298. 299. - finish_request(request, client_address) 300. 301. Class variables that may be overridden by derived classes or 302. instances: 303. 304. - address_family 305. - socket_type 306. - request_queue_size (only for stream sockets) 307. - allow_reuse_address 308. 309. Instance variables: 310. 311. - server_address 312. - RequestHandlerClass 313. - socket 314. 315. """ 316. 317. address_family = socket.AF_INET 318. 319. socket_type = socket.SOCK_STREAM 320. 321. request_queue_size = 5 322. 323. allow_reuse_address = False 324. 325. def __init__(self, server_address, RequestHandlerClass): 326. """Constructor. May be extended, do not override.""" 327. BaseServer.__init__(self, server_address, RequestHandlerClass) 328. self.socket = socket.socket(self.address_family, 329. self.socket_type) 330. self.server_bind() 331. self.server_activate() 332. 333. def server_bind(self): 334. """Called by constructor to bind the socket. 335. 336. May be overridden. 337. 338. """ 339. if self.allow_reuse_address: 340. self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) 341. self.socket.bind(self.server_address) 342. 343. def server_activate(self): 344. """Called by constructor to activate the server. 345. 346. May be overridden. 347. 348. """ 349. self.socket.listen(self.request_queue_size) 350. 351. def server_close(self): 352. """Called to clean-up the server. 353. 354. May be overridden. 355. 356. """ 357. self.socket.close() 358. 359. def fileno(self): 360. """Return socket file number. 361. 362. Interface required by select(). 363. 364. """ 365. return self.socket.fileno() 366. 367. def get_request(self): 368. """Get the request and client address from the socket. 369. 370. May be overridden. 371. 372. """ 373. return self.socket.accept() 374. 375. def close_request(self, request): 376. """Called to clean up an individual request.""" 377. request.close() 378. 379. 380. class UDPServer(TCPServer): 381. 382. """UDP server class.""" 383. 384. allow_reuse_address = False 385. 386. socket_type = socket.SOCK_DGRAM 387. 388. max_packet_size = 8192 389. 390. def get_request(self): 391. data, client_addr = self.socket.recvfrom(self.max_packet_size) 392. return (data, self.socket), client_addr 393. 394. def server_activate(self): 395. # No need to call listen() for UDP. 396. pass 397. 398. def close_request(self, request): 399. # No need to close anything. 400. pass 401. 402. class ForkingMixIn: 403. 404. """Mix-in class to handle each request in a new process.""" 405. 406. active_children = None 407. max_children = 40 408. 409. def collect_children(self): 410. """Internal routine to wait for died children.""" 411. while self.active_children: 412. if len(self.active_children) < self.max_children: 413. options = os.WNOHANG 414. else: 415. # If the maximum number of children are already 416. # running, block while waiting for a child to exit 417. options = 0 418. try: 419. pid, status = os.waitpid(0, options) 420. except os.error: 421. pid = None 422. if not pid: break 423. self.active_children.remove(pid) 424. 425. def process_request(self, request, client_address): 426. """Fork a new subprocess to process the request.""" 427. self.collect_children() 428. pid = os.fork() 429. if pid: 430. # Parent process 431. if self.active_children is None: 432. self.active_children = [] 433. self.active_children.append(pid) 434. self.close_request(request) 435. return 436. else: 437. # Child process. 438. # This must never return, hence os._exit()! 439. try: 440. self.finish_request(request, client_address) 441. os._exit(0) 442. except: 443. try: 444. self.handle_error(request, client_address) 445. finally: 446. os._exit(1) 447. 448. 449. class ThreadingMixIn: 450. """Mix-in class to handle each request in a new thread.""" 451. 452. # Decides how threads will act upon termination of the 453. # main process 454. daemon_threads = False 455. 456. def process_request_thread(self, request, client_address): 457. """Same as in BaseServer but as a thread. 458. 459. In addition, exception handling is done here. 460. 461. """ 462. try: 463. self.finish_request(request, client_address) 464. self.close_request(request) 465. except: 466. self.handle_error(request, client_address) 467. self.close_request(request) 468. 469. def process_request(self, request, client_address): 470. """Start a new thread to process the request.""" 471. import threading 472. t = threading.Thread(target = self.process_request_thread, 473. args = (request, client_address)) 474. if self.daemon_threads: 475. t.setDaemon (1) 476. t.start() 477. 478. 479. class ForkingUDPServer(ForkingMixIn, UDPServer): pass 480. class ForkingTCPServer(ForkingMixIn, TCPServer): pass 481. 482. class ThreadingUDPServer(ThreadingMixIn, UDPServer): pass 483. class ThreadingTCPServer(ThreadingMixIn, TCPServer): pass 484. 485. if hasattr(socket, 'AF_UNIX'): 486. 487. class UnixStreamServer(TCPServer): 488. address_family = socket.AF_UNIX 489. 490. class UnixDatagramServer(UDPServer): 491. address_family = socket.AF_UNIX 492. 493. class ThreadingUnixStreamServer(ThreadingMixIn, UnixStreamServer): pass 494. 495. class ThreadingUnixDatagramServer(ThreadingMixIn, UnixDatagramServer): pass 496. 497. class BaseRequestHandler: 498. 499. """Base class for request handler classes. 500. 501. This class is instantiated for each request to be handled. The 502. constructor sets the instance variables request, client_address 503. and server, and then calls the handle() method. To implement a 504. specific service, all you need to do is to derive a class which 505. defines a handle() method. 506. 507. The handle() method can find the request as self.request, the 508. client address as self.client_address, and the server (in case it 509. needs access to per-server information) as self.server. Since a 510. separate instance is created for each request, the handle() method 511. can define arbitrary other instance variariables. 512. 513. """ 514. 515. def __init__(self, request, client_address, server): 516. self.request = request 517. self.client_address = client_address 518. self.server = server 519. try: 520. self.setup() 521. self.handle() 522. self.finish() 523. finally: 524. sys.exc_traceback = None # Help garbage collection 525. 526. def setup(self): 527. pass 528. 529. def handle(self): 530. pass 531. 532. def finish(self): 533. pass 534. 535. 536. # The following two classes make it possible to use the same service 537. # class for stream or datagram servers. 538. # Each class sets up these instance variables: 539. # - rfile: a file object from which receives the request is read 540. # - wfile: a file object to which the reply is written 541. # When the handle() method returns, wfile is flushed properly 542. 543. 544. class StreamRequestHandler(BaseRequestHandler): 545. 546. """Define self.rfile and self.wfile for stream sockets.""" 547. 548. # Default buffer sizes for rfile, wfile. 549. # We default rfile to buffered because otherwise it could be 550. # really slow for large data (a getc() call per byte); we make 551. # wfile unbuffered because (a) often after a write() we want to 552. # read and we need to flush the line; (b) big writes to unbuffered 553. # files are typically optimized by stdio even when big reads 554. # aren't. 555. rbufsize = -1 556. wbufsize = 0 557. 558. def setup(self): 559. self.connection = self.request 560. self.rfile = self.connection.makefile('rb', self.rbufsize) 561. self.wfile = self.connection.makefile('wb', self.wbufsize) 562. 563. def finish(self): 564. if not self.wfile.closed: 565. self.wfile.flush() 566. self.wfile.close() 567. self.rfile.close() 568. 569. 570. class DatagramRequestHandler(BaseRequestHandler): 571. 572. # XXX Regrettably, I cannot get this working on Linux; 573. # s.recvfrom() doesn't return a meaningful client address. 574. 575. """Define self.rfile and self.wfile for datagram sockets.""" 576. 577. def setup(self): 578. import StringIO 579. self.packet, self.socket = self.request 580. self.rfile = StringIO.StringIO(self.packet) 581. self.wfile = StringIO.StringIO() 582. 583. def finish(self): 584. self.socket.sendto(self.wfile.getvalue(), self.client_address)