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from datetime import timedelta |
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from datetime import datetime |
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import time |
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import struct |
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from opcua import Subscription |
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from opcua import ua |
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def datetime_to_bytes(dt): |
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time_float = time.mktime(dt.timetuple()) + dt.microsecond / 1E6 |
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return struct.pack("!L", time_float) |
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def bytes_to_datetime(data): |
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time_float = struct.unpack('!L', data)[0] |
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return datetime.fromtimestamp(time_float) |
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class HistoryStorageInterface(object): |
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""" |
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Interface of a history backend |
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""" |
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def new_node(self, node, period, count=0): |
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raise NotImplementedError |
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def save_datavalue(self, node, datavalue): |
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raise NotImplementedError |
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def read_datavalues(self, node, start, end, nb_values): |
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raise NotImplementedError |
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def new_event(self, event, period): |
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raise NotImplementedError |
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def save_event(self, event): |
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raise NotImplementedError |
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def read_events(self, start, end, evfilter): |
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raise NotImplementedError |
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class HistoryDict(HistoryStorageInterface): |
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""" |
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very minimal history backend storing data in memory using a Python dictionnary |
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""" |
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def __init__(self): |
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self._datachanges = {} |
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self._datachanges_period = {} |
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self._events = {} |
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def new_node(self, node, period, count=0): |
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self._datachanges[node] = [] |
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self._datachanges_period[node] = period, count |
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def new_event(self, event, period): |
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self._events = [] |
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def save_datavalue(self, node, datavalue): |
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print("saving", node, datavalue) |
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data = self._datachanges[node] |
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period, count = self._datachanges_period[node] |
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data.append(datavalue) |
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now = datetime.now() |
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if period: |
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while now - data[0].ServerTimestamp > period: |
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data.pop(0) |
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if count and len(data) > count: |
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data = data[-count:] |
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def read_datavalues(self, node, start, end, nb_values): |
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if node not in self._datachanges: |
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return [] |
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else: |
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# FIME: improve algo |
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return [dv for dv in self._datachanges[node] if start <= dv.ServerTimestamp <= end] |
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def save_event(self, timestamp, event): |
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raise NotImplementedError |
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def read_events(self, start, end, evfilter): |
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raise NotImplementedError |
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class SubHandler(object): |
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def __init__(self, storage): |
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self.storage = storage |
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def datachange_notification(self, node, val, data): |
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self.storage.save_datavalue(node, data.monitored_item.Value) |
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def event_notification(self, event): |
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self.storage.save_event(event) |
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class HistoryManager(object): |
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def __init__(self, iserver): |
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self.iserver = iserver |
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self.storage = HistoryDict() |
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self._sub = None |
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self._handlers = {} |
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def set_storage(self, storage): |
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self.storage = storage |
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def _create_subscription(self, handler): |
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params = ua.CreateSubscriptionParameters() |
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params.RequestedPublishingInterval = 10 |
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params.RequestedLifetimeCount = 3000 |
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params.RequestedMaxKeepAliveCount = 10000 |
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params.MaxNotificationsPerPublish = 0 |
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params.PublishingEnabled = True |
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params.Priority = 0 |
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return Subscription(self.iserver.isession, params, handler) |
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def historize(self, node, period=timedelta(days=7), count=0): |
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if not self._sub: |
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self._sub = self._create_subscription(SubHandler(self.storage)) |
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if node in self._handlers: |
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raise ua.UaError("Node {} is allready historized".format(node)) |
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self.storage.new_node(node, period, count) |
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handler = self._sub.subscribe_data_change(node) |
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self._handlers[node] = handler |
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def dehistorize(self, node): |
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self._sub.unsubscribe(self._handlers[node]) |
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del(self._handlers[node]) |
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def read_history(self, params): |
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""" |
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Read history for a node |
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This is the part AttributeService, but implemented as its own service |
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since it requires more logic than other attribute service methods |
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""" |
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results = [] |
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for rv in params.NodesToRead: |
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res = self._read_history(params.HistoryReadDetails, rv) |
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results.append(res) |
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return results |
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def _read_history(self, details, rv): |
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""" read history for a node |
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""" |
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result = ua.HistoryReadResult() |
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if type(details) is ua.ReadRawModifiedDetails: |
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if details.IsReadModified: |
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result.HistoryData = ua.HistoryModifiedData() |
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# we do not support modified history by design so we return what we have |
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dv, cont = self._read_datavalue_history(rv, details) |
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result.HistoryData.DataValues = dv |
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result.ContinuationPoint = cont |
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else: |
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result.HistoryData = ua.HistoryData() |
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dv, cont = self._read_datavalue_history(rv, details) |
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result.HistoryData.DataValues = dv |
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result.ContinuationPoint = cont |
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elif type(details) is ua.ReadEventDetails: |
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result.HistoryData = ua.HistoryEvent() |
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# FIXME: filter is a cumbersome type, maybe transform it something easier |
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# to handle for storage |
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result.HistoryData.Events = self.storage.read_events(details.StartTime, |
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details.EndTime, |
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details.Filter) |
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else: |
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# we do not currently support the other types, clients can process data themselves |
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result.StatusCode = ua.StatusCode(ua.StatusCodes.BadNotImplemented) |
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return result |
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def read_datavalue_history(self, rv, details): |
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starttime = details.StartTime |
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if rv.ContinuationPoint: |
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# Spec says we should ignore details if cont point is present |
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# but they also say we can use cont point as timestamp to enable stateless |
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# implementation. This is contradictory, so we assume details is |
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# send correctly with continuation point |
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starttime = bytes_to_datetime(rv.ContinuationPoint) |
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dv, cont = self.storage.read_datavalues(rv.NodeId, |
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starttime, |
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details.EndTime, |
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details.NumValuesPerNode) |
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if cont: |
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cont = datetime_to_bytes(dv[-1].SourceTimeStamp) |
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# FIXME, parse index range and filter out if necesary |
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# rv.IndexRange |
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# rv.DataEncoding # xml or binary, seems spec say we can ignore that one |
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return dv, cont |
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190
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191
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1 |
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def update_history(self, params): |
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""" |
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193
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Update history for a node |
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194
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This is the part AttributeService, but implemented as its own service |
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since it requires more logic than other attribute service methods |
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""" |
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results = [] |
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198
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for details in params.HistoryUpdateDetails: |
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result = ua.HistoryUpdateResult() |
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# we do not accept to rewrite history |
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result.StatusCode = ua.StatusCode(ua.StatusCodes.BadNotWritable) |
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results.append(results) |
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return results |
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FreeOpcUa /
python-opcua
