Client cache exception

[dylanmcreynolds]

I have a tiled server that is serving tiff series data using https://github.com/bluesky/tiled/blob/6b1ee862e571a6e6493f5446652996600ec98638/tiled/adapters/tiff.py#L199.

Code that animates each 2D image eventually encounters a client cache exception, listed below. I will try also with similar data that's in h5 and see if I can reproduce there:

Traceback (most recent call last):
  File "/opt/miniconda3/envs/tiled_client/lib/python3.11/site-packages/tornado/ioloop.py", line 919, in _run
    val = self.callback()
          ^^^^^^^^^^^^^^^
  File "/opt/miniconda3/envs/tiled_client/lib/python3.11/site-packages/matplotlib/backend_bases.py", line 1226, in _on_timer
    ret = func(*args, **kwargs)
          ^^^^^^^^^^^^^^^^^^^^^
  File "/opt/miniconda3/envs/tiled_client/lib/python3.11/site-packages/matplotlib/animation.py", line 1426, in _step
    still_going = super()._step(*args)
                  ^^^^^^^^^^^^^^^^^^^^
  File "/opt/miniconda3/envs/tiled_client/lib/python3.11/site-packages/matplotlib/animation.py", line 1119, in _step
    self._draw_next_frame(framedata, self._blit)
  File "/opt/miniconda3/envs/tiled_client/lib/python3.11/site-packages/matplotlib/animation.py", line 1138, in _draw_next_frame
    self._draw_frame(framedata)
  File "/opt/miniconda3/envs/tiled_client/lib/python3.11/site-packages/matplotlib/animation.py", line 1767, in _draw_frame
    self._drawn_artists = self._func(framedata, *self._args)
                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/var/folders/gt/96zz11ls51542p5f9_cwq9w40000gn/T/ipykernel_11304/583051564.py", line 11, in updatefig
    im.set_array(spiral[i])
                 ~~~~~~^^^
  File "/opt/miniconda3/envs/tiled_client/lib/python3.11/site-packages/tiled/client/array.py", line 176, in __getitem__
    return self.read(slice)
           ^^^^^^^^^^^^^^^^
  File "/opt/miniconda3/envs/tiled_client/lib/python3.11/site-packages/tiled/client/array.py", line 256, in read
...
  File "/opt/miniconda3/envs/tiled_client/lib/python3.11/site-packages/tiled/client/cache.py", line 198, in load_content
    f"{len(content):_}",
       ^^^^^^^^^^^^
TypeError: object of type 'NoneType' has no len()```

[danielballan]

This is likely to be resolved when we completely rewrite the client cache, any day now. But to be safe I will leave this open so we can verify that.

[danielballan]

This entire module was erased and rewritten from scratch so I feel confident that this exact bug is gone. It would be still be useful for @dylanmcreynolds to confirm that the new cache interacts OK with his TIFF series.

[danielballan]

This is in v0.1.0a99 now. Note that the cache is (still) off by default, so to exercise it and test this you have to do something like:

from tiled.client.cache import Cache

c = from_uri("...", cache=Cache())

[danielballan]

It's been about a year and this hasn't come up again so I will assume that the cache rewrite resolved the issue.