A Monday 17 November 2008, Darren Dale escrigué:
> Hello,
>
> I have a client application that listens for events during data
> acquisition and updates a Table. Recently I started receiving errors
> part-way through a scan, once after 100 points, once after about 400:
>
>
> Traceback (most recent call last):
> File
> "/home/specuser/src/xpaxs/xpaxs/instrumentation/spec/runner.py", line
> 115, in update
> SpecEventsDispatcher.dispatch()
> File "/home/specuser/src/xpaxs/SpecClient/SpecEventsDispatcher.py",
> line 336, in dispatch
> receiver(args)
> File "/home/specuser/src/xpaxs/SpecClient/SpecEventsDispatcher.py",
> line 49, in __call__
> return robustApply(slot, arguments)
> File "/home/specuser/src/xpaxs/SpecClient/SpecEventsDispatcher.py",
> line 36, in robustApply
> return slot(*arguments[0:n_args])
> File "/home/specuser/src/xpaxs/SpecClient/SpecScan.py", line 114,
> in __newScanData
> self.newScanData(scanData)
> File "/home/specuser/src/xpaxs/xpaxs/instrumentation/spec/scan.py",
> line 103, in newScanData
> self._scanData.appendDataPoint(scanData)
> File
> "/home/specuser/src/xpaxs/xpaxs/frontends/xfs/fileinterface.py", line
> 214, in appendDataPoint
> row = self.h5Node.data.row
> File "/usr/lib/python2.5/site-packages/tables/group.py", line 854,
> in __getattr__
> return self._f_getChild(name)
> File "/usr/lib/python2.5/site-packages/tables/group.py", line 736,
> in _f_getChild
> return self._v_file._getNode(childPath)
> File "/usr/lib/python2.5/site-packages/tables/file.py", line 914,
> in _getNode
> "stale weak reference to dead node ``%s``" % parentPath
> AssertionError: stale weak reference to dead node ``/scan3/data``
>
>
> Could anyone please offer a suggestion, why would my "data" table
> become a dead node? At each point in the scan, I do something like:
>
> row = self.h5Node.data.row
>
> for key, val in data.iteritems():
> row[key] = val
>
> row.append()
> self.h5Node.data.flush()
>
> where self.h5Node is a reference to the "/scan3" group.
Mmh, this can be due to the way you are accessing the Row object that is
interacting badly with the LRUCache for nodes. One possible solution
is to bound the *Table* object instead of the Row one. Something like:
tbl = self.h5Node.data
for key, val in data.iteritems():
tbl.row[key] = val
tbl.row.append()
tbl.flush()
should work.
Hope that helps,
--
Francesc Alted
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