Failure to recover RE.md from files on startup

[prjemian]

Failures have been observed from this code block: https://github.com/BCDA-APS/bluesky_training/blob/d2b5f4cfa3bf356c20131f61bf91335430647592/bluesky/instrument/framework/initialize.py#L50-L61

When observed, the directory exists. Is there a mismatch between what is found and what is expected? In all observed cases so far, the problem is resolved by removing the directory defined by https://github.com/BCDA-APS/bluesky_training/blob/d2b5f4cfa3bf356c20131f61bf91335430647592/bluesky/instrument/iconfig.yml#L46

Needs more documentation, such as the exact exception traceback.

[prjemian]

[prjemian]

Thanks @strempfer for showing this example!

[prjemian]

Was able to reproduce locally by trying to open an older PersistentDict directory.

ls
beamline_id#22  conda_prefix#24  databroker_catalog#23  iconfig#21  instrument_name#27  login_id#26  pid#28  proposal_id#29  scan_id#25  versions#30

ipython

In [1]: from bluesky.utils import PersistentDict

In [2]: %xmode Verbose
Exception reporting mode: Verbose

In [3]: pd = PersistentDict(".")
---------------------------------------------------------------------------
FileNotFoundError                         Traceback (most recent call last)
Cell In[3], line 1
----> 1 pd = PersistentDict(".")
        PersistentDict = <class 'bluesky.utils.PersistentDict'>

File ~/.conda/envs/bluesky_2024_2/lib/python3.11/site-packages/bluesky/utils/__init__.py:775, in PersistentDict.__init__(self=<PersistentDict {}>, directory='.')
    773 self._func = zict.Func(self._dump, self._load, self._file)
    774 self._cache = {}
--> 775 self.reload()
        self = <PersistentDict {}>
    777 # Similar to flush() or _do_update(), but without reference to self
    778 # to avoid circular reference preventing collection.
    779 # NOTE: This still doesn't guarantee call on delete or gc.collect()!
    780 #       Explicitly call flush() if immediate write to disk required.
    781 def finalize(zfile, cache, dump):

File ~/.conda/envs/bluesky_2024_2/lib/python3.11/site-packages/bluesky/utils/__init__.py:841, in PersistentDict.reload(self=<PersistentDict {}>)
    839 def reload(self):
    840     """Force a reload from disk, overwriting current cache"""
--> 841     self._cache = dict(self._func.items())
        self._cache = {}
        self = <PersistentDict {}>
        self._func = <Func: _dump<->_load <File: ., mode="a", 10 elements>>

File ~/.conda/envs/bluesky_2024_2/lib/python3.11/site-packages/zict/func.py:74, in <genexpr>(.0=<generator object ItemsView.__iter__>)
     73 def items(self) -> Iterator[tuple[KT, VT]]:  # type: ignore
---> 74     return ((k, self.load(v)) for k, v in self.d.items())
        self.load = <function PersistentDict._load at 0x7f21045d8ae0>
        self = <Func: _dump<->_load <File: ., mode="a", 10 elements>>
        self.d = <File: ., mode="a", 10 elements>

File <frozen _collections_abc>:861, in __iter__(self=ItemsView(<File: ., mode="a", 10 elements>))

File ~/.conda/envs/bluesky_2024_2/lib/python3.11/site-packages/zict/file.py:82, in File.__getitem__(self=<File: ., mode="a", 10 elements>, key='versions#30')
     80     raise KeyError(key)
     81 fn = os.path.join(self.directory, _safe_key(key))
---> 82 with open(fn, "rb") as fh:
        fn = './versions%2330'
     83     if self.memmap:
     84         return memoryview(mmap.mmap(fh.fileno(), 0, access=mmap.ACCESS_READ))

FileNotFoundError: [Errno 2] No such file or directory: './versions%2330'

[prjemian]

The exception is correct, no such file ./versions%2330 exists. The existing file is named ./versions#30.

[prjemian]

RE_md_persistent_dict.zip

[prjemian]

A workaround for the situation is described.

The problem occurs for any file ending in #n (where n is an integer) in the persistent directory. The solution is to clean up the file names in the directory before opening with PersistentDict(directory). Clean-up involves stripping the problematic suffix. If a non-suffixed file exists, just delete the suffixed version. Should make log entries for any of these actions.