traverseda
/
cpython
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

SF Patch #102980, by Luke Kenneth Casson Leighton: BaseServer class 

for SocketServer.py (inherited by TCPServer)

Luke wrote:

  The socketserver code, with a little bit of tweaking, can be made
  sufficiently general to service "requests" of any kind, not just by sockets.
  The BaseServer class was created, for example, to poll a table in a MYSQL
  database every 2 seconds. each entry in the table can be allocated a
  Handler which deals with the entry.

  With this patch, using BaseServer and ThreadedServer classes, the creation
  of the server that reads and handles MySQL table entries instead of a
  socket was utterly trivial: about 50 lines of python code.

  You may consider this code to be utterly useless [why would anyone else
  want to do anything like this???] - you are entitled to your opinion. if you
  think so, then think of this: have you considered how to cleanly add SSL to
  the TCPSocketServer? What about using shared memory as the
  communications mechanism for a server, instead of sockets? What about
  communication using files?

  The SocketServer code is extremely good every useful. it's just that as it
  stands, it is tied to sockets, which is not as useful.

I heartily approve of this idea.
This commit is contained in:
Guido van Rossum 2001-01-19 00:44:41 +00:00
parent 3fa560b343
commit 90cb9067b8
1 changed files with 157 additions and 69 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

226
Lib/SocketServer.py
View File

@ -2,6 +2,8 @@
This module tries to capture the various aspects of defining a server:
For socket-based servers:
- address family:
- AF_INET: IP (Internet Protocol) sockets (default)
- AF_UNIX: Unix domain sockets
@ -9,6 +11,9 @@ This module tries to capture the various aspects of defining a server:
- socket type:
- SOCK_STREAM (reliable stream, e.g. TCP)
- SOCK_DGRAM (datagrams, e.g. UDP)
For request-based servers (including socket-based):
- client address verification before further looking at the request
(This is actually a hook for any processing that needs to look
at the request before anything else, e.g. logging)
@ -22,9 +27,14 @@ write: a synchronous TCP/IP server. This is bad class design, but
save some typing. (There's also the issue that a deep class hierarchy
slows down method lookups.)
There are four classes in an inheritance diagram that represent
There are five classes in an inheritance diagram, four of which represent
synchronous servers of four types:
+------------+
| BaseServer |
+------------+
|
v
+-----------+ +------------------+
| TCPServer |------->| UnixStreamServer |
+-----------+ +------------------+
@ -77,7 +87,7 @@ server is appropriate.
In some cases, it may be appropriate to process part of a request
synchronously, but to finish processing in a forked child depending on
the request data. This can be implemented by using a synchronous
server and doing an explicit fork in the request handler class's
server and doing an explicit fork in the request handler class
handle() method.
Another approach to handling multiple simultaneous requests in an
@ -87,7 +97,7 @@ explicit table of partially finished requests and to use select() to
decide which request to work on next (or whether to handle a new
incoming request). This is particularly important for stream services
where each client can potentially be connected for a long time (if
threads or subprocesses can't be used).
threads or subprocesses cannot be used).
Future work:
- Standard classes for Sun RPC (which uses either UDP or TCP)
@ -98,6 +108,14 @@ Future work:
XXX Open problems:
- What to do with out-of-band data?
BaseServer:
- split generic "request" functionality out into BaseServer class.
Copyright (C) 2000 Luke Kenneth Casson Leighton <lkcl@samba.org>
example: read entries from a SQL database (requires overriding
get_request() to return a table entry from the database).
entry is processed by a RequestHandlerClass.
"""
@ -109,7 +127,129 @@ import sys
import os
class TCPServer:
class BaseServer:
"""Base class for server classes.
Methods for the caller:
- __init__(server_address, RequestHandlerClass)
- serve_forever()
- handle_request() # if you do not use serve_forever()
- fileno() -> int # for select()
Methods that may be overridden:
- server_bind()
- server_activate()
- get_request() -> request, client_address
- verify_request(request, client_address)
- server_close()
- process_request(request, client_address)
- handle_error()
Methods for derived classes:
- finish_request(request, client_address)
Class variables that may be overridden by derived classes or
instances:
- address_family
- socket_type
- reuse_address
Instance variables:
- RequestHandlerClass
- socket
"""
def __init__(self, server_address, RequestHandlerClass):
"""Constructor. May be extended, do not override."""
self.server_address = server_address
self.RequestHandlerClass = RequestHandlerClass
def server_activate(self):
"""Called by constructor to activate the server.
May be overridden.
"""
pass
def serve_forever(self):
"""Handle one request at a time until doomsday."""
while 1:
self.handle_request()
# The distinction between handling, getting, processing and
# finishing a request is fairly arbitrary. Remember:
#
# - handle_request() is the top-level call. It calls
# get_request(), verify_request() and process_request()
# - get_request() is different for stream or datagram sockets
# - process_request() is the place that may fork a new process
# or create a new thread to finish the request
# - finish_request() instantiates the request handler class;
# this constructor will handle the request all by itself
def handle_request(self):
"""Handle one request, possibly blocking."""
try:
request, client_address = self.get_request()
except socket.error:
return
if self.verify_request(request, client_address):
try:
self.process_request(request, client_address)
except:
self.handle_error(request, client_address)
def verify_request(self, request, client_address):
"""Verify the request. May be overridden.
Return true if we should proceed with this request.
"""
return 1
def process_request(self, request, client_address):
"""Call finish_request.
Overridden by ForkingMixIn and ThreadingMixIn.
"""
self.finish_request(request, client_address)
def server_close(self):
"""Called to clean-up the server.
May be overridden.
"""
pass
def finish_request(self, request, client_address):
"""Finish one request by instantiating RequestHandlerClass."""
self.RequestHandlerClass(request, client_address, self)
def handle_error(self, request, client_address):
"""Handle an error gracefully. May be overridden.
The default is to print a traceback and continue.
"""
print '-'*40
print 'Exception happened during processing of request from',
print client_address
import traceback
traceback.print_exc() # XXX But this goes to stderr!
print '-'*40
class TCPServer(BaseServer):
"""Base class for various socket-based server classes.
@ -157,12 +297,11 @@ class TCPServer:
request_queue_size = 5
allow_reuse_address = 1
allow_reuse_address = 0
def __init__(self, server_address, RequestHandlerClass):
"""Constructor. May be extended, do not override."""
self.server_address = server_address
self.RequestHandlerClass = RequestHandlerClass
BaseServer.__init__(self, server_address, RequestHandlerClass)
self.socket = socket.socket(self.address_family,
self.socket_type)
self.server_bind()
@ -186,6 +325,14 @@ class TCPServer:
"""
self.socket.listen(self.request_queue_size)
def server_close(self):
"""Called to clean-up the server.
May be overridden.
"""
self.socket.close()
def fileno(self):
"""Return socket file number.
@ -194,34 +341,6 @@ class TCPServer:
"""
return self.socket.fileno()
def serve_forever(self):
"""Handle one request at a time until doomsday."""
while 1:
self.handle_request()
# The distinction between handling, getting, processing and
# finishing a request is fairly arbitrary. Remember:
#
# - handle_request() is the top-level call. It calls
# get_request(), verify_request() and process_request()
# - get_request() is different for stream or datagram sockets
# - process_request() is the place that may fork a new process
# or create a new thread to finish the request
# - finish_request() instantiates the request handler class;
# this constructor will handle the request all by itself
def handle_request(self):
"""Handle one request, possibly blocking."""
try:
request, client_address = self.get_request()
except socket.error:
return
if self.verify_request(request, client_address):
try:
self.process_request(request, client_address)
except:
self.handle_error(request, client_address)
def get_request(self):
"""Get the request and client address from the socket.
@ -230,44 +349,13 @@ class TCPServer:
"""
return self.socket.accept()
def verify_request(self, request, client_address):
"""Verify the request. May be overridden.
Return true if we should proceed with this request.
"""
return 1
def process_request(self, request, client_address):
"""Call finish_request.
Overridden by ForkingMixIn and ThreadingMixIn.
"""
self.finish_request(request, client_address)
def finish_request(self, request, client_address):
"""Finish one request by instantiating RequestHandlerClass."""
self.RequestHandlerClass(request, client_address, self)
def handle_error(self, request, client_address):
"""Handle an error gracefully. May be overridden.
The default is to print a traceback and continue.
"""
print '-'*40
print 'Exception happened during processing of request from',
print client_address
import traceback
traceback.print_exc()
print '-'*40
class UDPServer(TCPServer):
"""UDP server class."""
allow_reuse_address = 0
socket_type = socket.SOCK_DGRAM
max_packet_size = 8192
@ -318,7 +406,7 @@ class ForkingMixIn:
# Child process.
# This must never return, hence os._exit()!
try:
self.socket.close()
self.server_close()
self.finish_request(request, client_address)
os._exit(0)
except: