More configurable history read functions and recursive history reading

[HarrySky]

Hi, I was trying to use methods related to reading history from server and found some usability issues.

• Right now you can use Node.read_raw_history to get history data in some range that ALWAYS includes bounds (ReturnBounds is set to True and not configurable)
• Even if ContinuationPoint is returned inside Node.read_raw_history request from Node.history_read - it is unused and not returned from method (you can't continue reading history if there is more than what was returned)

To address those issues I patch ContinuationPoint into Node.history_read then copy and change Node.read_raw_history code so that it reads all history available and sets details.ReturnBounds to False (see Minimal Reproducible Example below)

Can some of this configuration (ReturnBounds and ContinuationPoint) be actually added to asyncua code or maybe some Node.read_history_recursive method added? I am ready to send a PR, need your advice and opinion

import asyncio
from datetime import datetime
from typing import Optional

from asyncua import Client, ua
from asyncua.common.node import Node
from asyncua.ua.uatypes import NodeId


async def patched_history_read(
    self: Node,
    details: ua.ReadRawModifiedDetails,
    # [PATCHED IN]
    continuation_point: Optional[bytes] = None,
):
    valueid = ua.HistoryReadValueId()
    valueid.NodeId = self.nodeid
    valueid.IndexRange = ''
    # [PATCHED IN]
    valueid.ContinuationPoint = continuation_point
    params = ua.HistoryReadParameters()
    params.HistoryReadDetails = details
    params.TimestampsToReturn = ua.TimestampsToReturn.Both
    params.ReleaseContinuationPoints = False
    params.NodesToRead.append(valueid)
    return (await self.server.history_read(params))[0]


Node.history_read = patched_history_read


async def main():
    opc_client = Client("opc.tcp://127.0.0.1:4840")
    await opc_client.connect()
    node = opc_client.get_node(NodeId(1, 1))

    # COPIED CODE FROM Node.read_raw_history:
    details = ua.ReadRawModifiedDetails()
    details.IsReadModified = False
    details.StartTime = datetime.fromtimestamp(0)
    details.EndTime = datetime.now()
    details.NumValuesPerNode = 0
    # This is not configurable in Node.read_raw_history!
    details.ReturnBounds = False

    # Loop that reads all history available
    continuation_point: Optional[bytes] = None
    while True:
        result = await node.history_read(details, continuation_point)
        result.StatusCode.check()
        continuation_point = result.ContinuationPoint
        history = result.HistoryData.DataValues
        for value in history:
            print(value)

        # No more data available
        if continuation_point is None:
            break


asyncio.run(main())

[oroulet]

It is very hard to understand from new code, especially when I have not seen/used the hisotry code for years.. But a PR is welcome and then we will better see your proposed changes

[HarrySky]

Will send draft PR soon 👍

[HarrySky]

Done! PR #559