The Evolution of Finger: pluggable backends

  1. Introduction
  2. Another Back-end
  3. Yet Another Back-end: Doing the Standard Thing

Introduction

This is the fifth part of the Twisted tutorial Twisted from Scratch, or The Evolution of Finger.

In this part we will add new several new backends to our finger service using the component-based architecture developed in The Evolution of Finger: moving to a component based architecture. This will show just how convenient it is to implement new back-ends when we move to a component based architecture. Note that here we also use an interface we previously wrote, FingerSetterFactory, by supporting one single method. We manage to preserve the service's ignorance of the network.

Another Back-end

Full source code here:

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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292

# Do everything properly, and componentize from twisted.application import internet, service from twisted.internet import protocol, reactor, defer, utils from twisted.words.protocols import irc from twisted.protocols import basic from twisted.python import components from twisted.web import resource, server, static, xmlrpc from zope.interface import Interface, implements import cgi import pwd class IFingerService(Interface): def getUser(user): """ Return a deferred returning a string. """ def getUsers(): """ Return a deferred returning a list of strings. """ class IFingerSetterService(Interface): def setUser(user, status): """ Set the user's status to something. """ class IFingerSetterService(Interface): def setUser(user, status): """ Set the user's status to something. """ def catchError(err): return "Internal error in server" class FingerProtocol(basic.LineReceiver): def lineReceived(self, user): d = self.factory.getUser(user) d.addErrback(catchError) def writeValue(value): self.transport.write(value+'\r\n') self.transport.loseConnection() d.addCallback(writeValue) class IFingerFactory(Interface): def getUser(user): """ Return a deferred returning a string. """ def buildProtocol(addr): """ Return a protocol returning a string. """ class FingerFactoryFromService(protocol.ServerFactory): implements(IFingerFactory) protocol = FingerProtocol def __init__(self, service): self.service = service def getUser(self, user): return self.service.getUser(user) components.registerAdapter(FingerFactoryFromService, IFingerService, IFingerFactory) class FingerSetterProtocol(basic.LineReceiver): def connectionMade(self): self.lines = [] def lineReceived(self, line): self.lines.append(line) def connectionLost(self, reason): if len(self.lines) == 2: self.factory.setUser(*self.lines) class IFingerSetterFactory(Interface): def setUser(user, status): """ Return a deferred returning a string. """ def buildProtocol(addr): """ Return a protocol returning a string. """ class FingerSetterFactoryFromService(protocol.ServerFactory): implements(IFingerSetterFactory) protocol = FingerSetterProtocol def __init__(self, service): self.service = service def setUser(self, user, status): self.service.setUser(user, status) components.registerAdapter(FingerSetterFactoryFromService, IFingerSetterService, IFingerSetterFactory) class IRCReplyBot(irc.IRCClient): def connectionMade(self): self.nickname = self.factory.nickname irc.IRCClient.connectionMade(self) def privmsg(self, user, channel, msg): user = user.split('!')[0] if self.nickname.lower() == channel.lower(): d = self.factory.getUser(msg) d.addErrback(catchError) d.addCallback(lambda m: "Status of %s: %s" % (msg, m)) d.addCallback(lambda m: self.msg(user, m)) class IIRCClientFactory(Interface): """ @ivar nickname """ def getUser(user): """ Return a deferred returning a string. """ def buildProtocol(addr): """ Return a protocol. """ class IRCClientFactoryFromService(protocol.ClientFactory): implements(IIRCClientFactory) protocol = IRCReplyBot nickname = None def __init__(self, service): self.service = service def getUser(self, user): return self.service.getUser(user) components.registerAdapter(IRCClientFactoryFromService, IFingerService, IIRCClientFactory) class UserStatusTree(resource.Resource): implements(resource.IResource) def __init__(self, service): resource.Resource.__init__(self) self.service = service self.putChild('RPC2', UserStatusXR(self.service)) def render_GET(self, request): d = self.service.getUsers() def formatUsers(users): l = ['<li><a href="%s">%s</a></li>' % (user, user) for user in users] return '<ul>'+''.join(l)+'</ul>' d.addCallback(formatUsers) d.addCallback(request.write) d.addCallback(lambda _: request.finish()) return server.NOT_DONE_YET def getChild(self, path, request): if path=="": return UserStatusTree(self.service) else: return UserStatus(path, self.service) components.registerAdapter(UserStatusTree, IFingerService, resource.IResource) class UserStatus(resource.Resource): def __init__(self, user, service): resource.Resource.__init__(self) self.user = user self.service = service def render_GET(self, request): d = self.service.getUser(self.user) d.addCallback(cgi.escape) d.addCallback(lambda m: '<h1>%s</h1>'%self.user+'<p>%s</p>'%m) d.addCallback(request.write) d.addCallback(lambda _: request.finish()) return server.NOT_DONE_YET class UserStatusXR(xmlrpc.XMLRPC): def __init__(self, service): xmlrpc.XMLRPC.__init__(self) self.service = service def xmlrpc_getUser(self, user): return self.service.getUser(user) class FingerService(service.Service): implements(IFingerService) def __init__(self, filename): self.filename = filename self.users = {} def _read(self): self.users.clear() for line in file(self.filename): user, status = line.split(':', 1) user = user.strip() status = status.strip() self.users[user] = status self.call = reactor.callLater(30, self._read) def getUser(self, user): return defer.succeed(self.users.get(user, "No such user")) def getUsers(self): return defer.succeed(self.users.keys()) def startService(self): self._read() service.Service.startService(self) def stopService(self): service.Service.stopService(self) self.call.cancel() # Another back-end class LocalFingerService(service.Service): implements(IFingerService) def getUser(self, user): # need a local finger daemon running for this to work return utils.getProcessOutput("finger", [user]) def getUsers(self): return defer.succeed([]) application = service.Application('finger', uid=1, gid=1) f = LocalFingerService() serviceCollection = service.IServiceCollection(application) internet.TCPServer(79, IFingerFactory(f) ).setServiceParent(serviceCollection) internet.TCPServer(8000, server.Site(resource.IResource(f)) ).setServiceParent(serviceCollection) i = IIRCClientFactory(f) i.nickname = 'fingerbot' internet.TCPClient('irc.freenode.org', 6667, i ).setServiceParent(serviceCollection)

We've already written this, but now we get more for less work: the network code is completely separate from the back-end.

Yet Another Back-end: Doing the Standard Thing

Full source code here:

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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305

# Do everything properly, and componentize from twisted.application import internet, service from twisted.internet import protocol, reactor, defer, utils from twisted.words.protocols import irc from twisted.protocols import basic from twisted.python import components from twisted.web import resource, server, static, xmlrpc from zope.interface import Interface, implements import cgi import pwd import os class IFingerService(Interface): def getUser(user): """ Return a deferred returning a string. """ def getUsers(): """ Return a deferred returning a list of strings. """ class IFingerSetterService(Interface): def setUser(user, status): """ Set the user's status to something. """ class IFingerSetterService(Interface): def setUser(user, status): """ Set the user's status to something. """ def catchError(err): return "Internal error in server" class FingerProtocol(basic.LineReceiver): def lineReceived(self, user): d = self.factory.getUser(user) d.addErrback(catchError) def writeValue(value): self.transport.write(value+'\r\n') self.transport.loseConnection() d.addCallback(writeValue) class IFingerFactory(Interface): def getUser(user): """ Return a deferred returning a string. """ def buildProtocol(addr): """ Return a protocol returning a string. """ class FingerFactoryFromService(protocol.ServerFactory): implements(IFingerFactory) protocol = FingerProtocol def __init__(self, service): self.service = service def getUser(self, user): return self.service.getUser(user) components.registerAdapter(FingerFactoryFromService, IFingerService, IFingerFactory) class FingerSetterProtocol(basic.LineReceiver): def connectionMade(self): self.lines = [] def lineReceived(self, line): self.lines.append(line) def connectionLost(self, reason): if len(self.lines) == 2: self.factory.setUser(*self.lines) class IFingerSetterFactory(Interface): def setUser(user, status): """ Return a deferred returning a string. """ def buildProtocol(addr): """ Return a protocol returning a string. """ class FingerSetterFactoryFromService(protocol.ServerFactory): implements(IFingerSetterFactory) protocol = FingerSetterProtocol def __init__(self, service): self.service = service def setUser(self, user, status): self.service.setUser(user, status) components.registerAdapter(FingerSetterFactoryFromService, IFingerSetterService, IFingerSetterFactory) class IRCReplyBot(irc.IRCClient): def connectionMade(): self.nickname = self.factory.nickname irc.IRCClient.connectionMade(self) def privmsg(self, user, channel, msg): user = user.split('!')[0] if self.nickname.lower() == channel.lower(): d = self.factory.getUser(msg) d.addErrback(catchError) d.addCallback(lambda m: "Status of %s: %s" % (msg, m)) d.addCallback(lambda m: self.msg(user, m)) class IIRCClientFactory(Interface): """ @ivar nickname """ def getUser(user): """ Return a deferred returning a string. """ def buildProtocol(addr): """ Return a protocol. """ class IRCClientFactoryFromService(protocol.ClientFactory): implements(IIRCClientFactory) protocol = IRCReplyBot nickname = None def __init__(self, service): self.service = service def getUser(self, user): return self.service.getUser(user) components.registerAdapter(IRCClientFactoryFromService, IFingerService, IIRCClientFactory) class UserStatusTree(resource.Resource): implements(resource.IResource) def __init__(self, service): resource.Resource.__init__(self) self.service = service self.putChild('RPC2', UserStatusXR(self.service)) def render_GET(self, request): d = self.service.getUsers() def formatUsers(users): l = ['<li><a href="%s">%s</a></li>' % (user, user) for user in users] return '<ul>'+''.join(l)+'</ul>' d.addCallback(formatUsers) d.addCallback(request.write) d.addCallback(lambda _: request.finish()) return server.NOT_DONE_YET def getChild(self, path, request): if path=="": return UserStatusTree(self.service) else: return UserStatus(path, self.service) components.registerAdapter(UserStatusTree, IFingerService, resource.IResource) class UserStatus(resource.Resource): def __init__(self, user, service): resource.Resource.__init__(self) self.user = user self.service = service def render_GET(self, request): d = self.service.getUser(self.user) d.addCallback(cgi.escape) d.addCallback(lambda m: '<h1>%s</h1>'%self.user+'<p>%s</p>'%m) d.addCallback(request.write) d.addCallback(lambda _: request.finish()) return server.NOT_DONE_YET class UserStatusXR(xmlrpc.XMLRPC): def __init__(self, service): xmlrpc.XMLRPC.__init__(self) self.service = service def xmlrpc_getUser(self, user): return self.service.getUser(user) class FingerService(service.Service): implements(IFingerService) def __init__(self, filename): self.filename = filename self.users = {} def _read(self): self.users.clear() for line in file(self.filename): user, status = line.split(':', 1) user = user.strip() status = status.strip() self.users[user] = status self.call = reactor.callLater(30, self._read) def getUser(self, user): return defer.succeed(self.users.get(user, "No such user")) def getUsers(self): return defer.succeed(self.users.keys()) def startService(self): self._read() service.Service.startService(self) def stopService(self): service.Service.stopService(self) self.call.cancel() # Yet another back-end class LocalFingerService(service.Service): implements(IFingerService) def getUser(self, user): user = user.strip() try: entry = pwd.getpwnam(user) except KeyError: return defer.succeed("No such user") try: f = file(os.path.join(entry[5],'.plan')) except (IOError, OSError): return defer.succeed("No such user") data = f.read() data = data.strip() f.close() return defer.succeed(data) def getUsers(self): return defer.succeed([]) application = service.Application('finger', uid=1, gid=1) f = LocalFingerService() serviceCollection = service.IServiceCollection(application) internet.TCPServer(79, IFingerFactory(f) ).setServiceParent(serviceCollection) internet.TCPServer(8000, server.Site(resource.IResource(f)) ).setServiceParent(serviceCollection) i = IIRCClientFactory(f) i.nickname = 'fingerbot' internet.TCPClient('irc.freenode.org', 6667, i ).setServiceParent(serviceCollection)

Not much to say except that now we can be churn out backends like crazy. Feel like doing a back-end for Advogato, for example? Dig out the XML-RPC client support Twisted has, and get to work!

Index

Version: 11.0.0 Site Meter