[Kst] 2.0.8

[Barth Netterfield]

The fact that the problems happen with the configuration, below, and not on my 
system re-enforces my belief that this is file system race-condition related.

kst decides that a file has been re-written/replaced and needs to be re-read 
from the beginning when it has shrunk.  Apparently, in the configuration below, 
if a file is being written to, it can appear smaller than it was.  As far as I 
know, this can not happen in Linux.

As a hack (as opposed to a fix, which might require re-writing the file system I 
suspect) we could tell the data vector to delay reading a few times if the 
data source reports back with a shrunk file - and not try a re-read until it 
has failed a few times.  This will (dramatically?) reduce the rate of failures 
but since the problems are unpredictable, it won't formally fully fix the 
problem.

I will commit a hack shortly.

The second problem (reading zeros) is harder to fix (but probably caused by the 
same thing).  I will think about it. 

cbn

On February 22, 2014 12:22:47 PM Ben Lewis wrote:
> 
> I have a USB memory stick plugged into the PC where the data is generated.
> Data is collected to a RAM buffer and then written to a CSV file on the
> memory stick. The memory stick has Windows file sharing enabled so that it
> is accessible over the local network.
> Kst runs on a different PC. The shared drive (memory stick) on the remote PC
> is mapped to a local drive. Kst then reads the CSV file as if it were a
> local file (with update type set to "time interval") The connection between
> the two PCs is either via a LAN cable or an Ad-hoc WiFi connection. The
> problem exists under both cases.
> 
> Remote System (where CSV data file is generated)
> ----------------------------------------------------------------
> OS: WindowsXP embedded (32bit)
> File System: Data is written to a USB memory stick, formatted with NTFS
> Data Accumulation Rate:
>       fields/row: 5
>       characters per field: 7
>       bytes per row: 41
>       rows per second: 1500
> 
> I've attached the first 100 lines of a data file.
> 
> Local System (where Kst is run)
> ----------------------------------------
> OS: Windows7 (64bit)
> File System: Remote NTFS drive is mapped to local drive
> Kst: 64bit build
> 
> >> *   "Out of Memory" error
> >> http://kde.6490.n7.nabble.com/Out-of-memory-error-td1555215.html The
> >> error
> >> message has been improved but the message still appears when it
> >> shouldn't.
> > 
> > I also can't reproduce this.  Can you give me details (OS, file size)?  Is
> > the data being updated real time during the read?  At what rate?
> 
> Same as above
> 
> >>    * I sometimes get snippets of data missing in a live plot. If I
> >>    restart
> >> 
> >> Kst and reload the data there are no missing bits. This seems to happen
> >> when there is a large amount of network traffic (my data file is not on a
> >> local disk). This is hard to reproduce so it's probably not worth
> >> worrying
> >> about at this stage.
> > 
> > Yes.... are you using smb or nfs?  Is it at all correlated with the first
> > bug?
> I'm using Window file sharing.
> It could very well be related to the first bug but I have no way of telling.

-- 
Barth Netterfield
University of Toronto
416-845-0946