Cache data

Engineering 🇬🇧
andras-mozes
2020-12-17
2020-12-22

  • andras-mozes - 2020-12-17

    Hello,

    What would be an ideal solution to save data before processing them.

    I mean I am reading strUserID and I want to persist them before saving them to a MySQL database.

    Actually I would like to use 2 tasks. One collecting strUserID while another one handling MySQL connection and sending of them.

    The problem that I would like to save the strUserID before sending them thus in case of power outage, I didn't lose any strUserID.

    I don't know whether to use collections (persisted) or persistent manager (as txt) or var persistent?

    Thanks for your help in advance.

    BR!

     

  • i-campbell

    i-campbell - 2020-12-22

    If the requirement is really not to lose any then the file-based persistence manager may be too slow for you.
    Use a controller with non-volatile ram setup for retain data. Then use a circular array stored in VAR PERSISTENT. The array size should be as big as the maximum number of userids you intend to buffer.

     
    👍
    1

    • andras-mozes - 2020-12-22 
      {attribute 'qualified_only'}
VAR_GLOBAL PERSISTENT RETAIN
    aAuthData : ARRAY[0..300] OF AuthData;
END_VAR

      How could I set-up a circular array?
      Would you mind showing some resources, examples? :)

      Thanks for your help in advance.

       

  • i-campbell

    i-campbell - 2020-12-22 
    VAR_GLOBAL PERSISTENT RETAIN
    aAuthData : ARRAY[0..300] OF AuthData;
    udiInsertIndex : UDINT := 300;
    udiReadIndex : UDINT := 300;
    processed : BOOL := TRUE;
END_VAR

//Adding a value:
IF xNewData THEN
    udiInsertIndex := (udiInsertIndex+1) MOD 301;
    aAuthData[udiInsertIndex] := newAuthData;
    xNewData := FALSE;
END_IF

//Checking for new values:
IF udiReadIndex <> udiInsertIndex AND processed THEN
    udiReadIndex := (udiReadIndex+1) MOD 301;
    processed := FALSE;
END_IF

//Process the new value
IF NOT processed THEN
    //Process the value and set processed when finished
    DoSomethingWith(aAuthData[udiReadIndex], processed);
END_IF
     
    👍
    1

Log in to post a comment.