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Could not find the request epoch

Created by: SeanDS

When trying to retrieve data from our (NDS1) server with this script, I get a Could not find the request epoch error:

from gwpy.timeseries import TimeSeries
from matplotlib import pyplot as plt

data = TimeSeries.fetch(start="yesterday", end="now", channel="G2:PEM-BASE_PART_300", host="pt-firefly", port=8088)
plt.plot(data)
plt.show()
(gwpy-dev) sean@totoro /tmp $ python tmp.py
Traceback (most recent call last):
  File "tmp.py", line 4, in <module>
    data = TimeSeries.fetch(start="yesterday", end="now", channel="G2:PEM-BASE_PART_300", host="pt-firefly", port=8088)
  File "/home/sean/Workspace/anaconda/envs/gwpy-dev/lib/python3.7/site-packages/gwpy/timeseries/core.py", line 379, in fetch
    allow_tape=allow_tape, type=type, dtype=dtype)[str(channel)]
  File "/home/sean/Workspace/anaconda/envs/gwpy-dev/lib/python3.7/site-packages/gwpy/timeseries/core.py", line 1187, in fetch
    series_class=cls.EntryClass).crop(start, end)
  File "/home/sean/Workspace/anaconda/envs/gwpy-dev/lib/python3.7/site-packages/gwpy/io/nds2.py", line 351, in wrapped_func
    return func(*args, **kwargs)
  File "/home/sean/Workspace/anaconda/envs/gwpy-dev/lib/python3.7/site-packages/gwpy/timeseries/io/nds2.py", line 117, in fetch
    unique=True)
  File "/home/sean/Workspace/anaconda/envs/gwpy-dev/lib/python3.7/site-packages/gwpy/io/nds2.py", line 351, in wrapped_func
    return func(*args, **kwargs)
  File "/home/sean/Workspace/anaconda/envs/gwpy-dev/lib/python3.7/site-packages/gwpy/io/nds2.py", line 380, in wrapped_func
    return func(*args, **kwargs)
  File "/home/sean/Workspace/anaconda/envs/gwpy-dev/lib/python3.7/site-packages/gwpy/io/nds2.py", line 366, in wrapped_func
    return func(*args, **kwargs)
  File "/home/sean/Workspace/anaconda/envs/gwpy-dev/lib/python3.7/site-packages/gwpy/io/nds2.py", line 449, in find_channels
    connection.set_epoch(*epoch)
  File "/home/sean/Workspace/anaconda/envs/gwpy-dev/lib/python3.7/site-packages/nds2.py", line 3351, in set_epoch
    return _nds2.connection_set_epoch(self, *args)
RuntimeError: Low level daq error occured [1]: Unspecified error
Could not find the request epoch

This error occurs both on 0.14.2 (conda) and 0.15.0 (pip).

It appears the connection to the NDS server is taking place, from the server logs:

[Mon Apr 29 14:48:33 2019] connection on port 38943 from 10.117.14.225;
fd=42 req_tp n_gds_servers=16; node[0]=33 tpnum[0]=30183
decimation flag=1
[Mon Apr 29 14:48:33 2019] connection on fd 42 closed
[Mon Apr 29 14:48:33 2019] connection on port 38943 from 10.117.14.225;
fd=41 [Mon Apr 29 14:48:33 2019] ->37: version
[Mon Apr 29 14:48:33 2019] ->37: revision
[Mon Apr 29 14:48:33 2019] ->37: quit
[Mon Apr 29 14:48:33 2019] connection on fd 41 closed

However it appears gwpy or the python-nds2-client is deciding to quit after asking the server for its version and revision.

With nds_query, I can successfully retrieve a list of channels from the same machine running the above script:

> nds_query -1 -n pt-firefly -p 8088 -l
...huge list of channels...