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1 import logging, time
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2 import traceback
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3 from rdflib import ConjunctiveGraph
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4 from rdflib.parser import StringInputSource
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5 from twisted.internet import reactor, defer
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6
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7 from rdfdb.patch import Patch
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8 from twisted_sse.eventsource import EventSource
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9
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10 from .patchablegraph import patchFromJson
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11
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12 log = logging.getLogger('fetch')
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13
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14 class PatchSource(object):
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15 """wrap EventSource so it emits Patch objects and has an explicit stop method."""
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16 def __init__(self, url, agent):
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17 self.url = str(url)
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18
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19 # add callbacks to these to learn if we failed to connect
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20 # (approximately) or if the ccnnection was unexpectedly lost
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21 self.connectionFailed = defer.Deferred()
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22 self.connectionLost = defer.Deferred()
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23
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24 self._listeners = set()
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25 log.info('start read from %s', url)
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26 self._startReadTime = time.time()
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27 self._patchesReceived = 0 # including fullgraph
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28 # note: fullGraphReceived isn't guaranteed- the stream could
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29 # start with patches
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30 self._fullGraphReceived = False
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31 self._eventSource = EventSource(url.toPython().encode('utf8'),
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32 userAgent=agent)
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33
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34 self._eventSource.addEventListener(b'fullGraph', self._onFullGraph)
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35 self._eventSource.addEventListener(b'patch', self._onPatch)
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36 self._eventSource.onerror(self._onError)
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37 self._eventSource.onConnectionLost = self._onDisconnect
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38
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39 def state(self):
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40 return {
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41 'url': self.url,
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42 'fullGraphReceived': self._fullGraphReceived,
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43 'patchesReceived': self._patchesReceived,
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44 'time': {
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45 'open': getattr(self, '_startReadTime', None),
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46 'fullGraph': getattr(self, '_fullGraphTime', None),
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47 'latestPatch': getattr(self, '_latestPatchTime', None),
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48 },
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49 'closed': self._eventSource is None,
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50 }
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51
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52 def addPatchListener(self, func):
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53 """
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54 func(patch, fullGraph=[true if the patch is the initial fullgraph])
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55 """
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56 self._listeners.add(func)
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57
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58 def stop(self):
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59 log.info('stop read from %s', self.url)
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60 try:
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61 self._eventSource.protocol.stopProducing() # needed?
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62 except AttributeError:
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63 pass
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64 self._eventSource = None
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65
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66 def _onDisconnect(self, reason):
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67 log.debug('PatchSource._onDisconnect from %s (%s)', self.url, reason)
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68 # skip this if we're doing a stop?
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69 self.connectionLost.callback(None)
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70
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71 def _onError(self, msg):
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72 log.debug('PatchSource._onError from %s %r', self.url, msg)
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73 if not self._fullGraphReceived:
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74 self.connectionFailed.callback(msg)
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75 else:
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76 self.connectionLost.callback(msg)
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77
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78 def _onFullGraph(self, message):
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79 try:
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80 g = ConjunctiveGraph()
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81 g.parse(StringInputSource(message), format='json-ld')
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82 p = Patch(addGraph=g)
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83 self._sendPatch(p, fullGraph=True)
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84 except Exception:
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85 log.error(traceback.format_exc())
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86 raise
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87 self._fullGraphReceived = True
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88 self._fullGraphTime = time.time()
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89 self._patchesReceived += 1
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90
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91 def _onPatch(self, message):
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92 try:
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93 p = patchFromJson(message)
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94 self._sendPatch(p, fullGraph=False)
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95 except:
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96 log.error(traceback.format_exc())
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97 raise
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98 self._latestPatchTime = time.time()
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99 self._patchesReceived += 1
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100
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101 def _sendPatch(self, p, fullGraph):
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102 log.debug('PatchSource %s received patch %s (fullGraph=%s)',
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103 self.url, p.shortSummary(), fullGraph)
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104 for lis in self._listeners:
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105 lis(p, fullGraph=fullGraph)
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106
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107 def __del__(self):
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108 if self._eventSource:
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109 raise ValueError("PatchSource wasn't stopped before del")
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110
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111 class ReconnectingPatchSource(object):
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112 """
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113 PatchSource api, but auto-reconnects internally and takes listener
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114 at init time to not miss any patches. You'll get another
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115 fullGraph=True patch if we have to reconnect.
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116
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117 todo: generate connection stmts in here
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118 """
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119 def __init__(self, url, listener, reconnectSecs=60, agent='unset'):
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120 # type: (str, Any, Any, str)
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121 self.url = url
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122 self._stopped = False
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123 self._listener = listener
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124 self.reconnectSecs = reconnectSecs
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125 self.agent = agent
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126 self._reconnect()
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127
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128 def _reconnect(self):
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129 if self._stopped:
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130 return
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131 self._ps = PatchSource(self.url, agent=self.agent)
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132 self._ps.addPatchListener(self._onPatch)
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133 self._ps.connectionFailed.addCallback(self._onConnectionFailed)
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134 self._ps.connectionLost.addCallback(self._onConnectionLost)
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135
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136 def _onPatch(self, p, fullGraph):
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137 self._listener(p, fullGraph=fullGraph)
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138
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139 def state(self):
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140 return {
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141 'reconnectedPatchSource': self._ps.state(),
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142 }
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143
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144 def stop(self):
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145 self._stopped = True
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146 self._ps.stop()
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147
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148 def _onConnectionFailed(self, arg):
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149 reactor.callLater(self.reconnectSecs, self._reconnect)
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150
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151 def _onConnectionLost(self, arg):
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152 reactor.callLater(self.reconnectSecs, self._reconnect)
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153
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