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ktbyers / netmiko

Multi-vendor library to simplify Paramiko SSH connections to network devices
MIT License
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fastiron - session preparation / _test_channel_read() not working after successful connection #3440

Closed johanek closed 3 months ago

johanek commented 3 months ago

Hello,

On Brocade ICX 6450 I have be getting the following error when running session_preparation():

---------------------------------------------------------------------------
ReadTimeout                               Traceback (most recent call last)
<ipython-input-6-2d99eca55c84> in <module>
----> 1 device._test_channel_read(pattern='')

~/.local/share/virtualenvs/napalm-examples-yv4OVgxK/lib/python3.9/site-packages/netmiko/base_connection.py in _test_channel_read(self, count, pattern)
   1239         new_data = ""
   1240         while i <= count:
-> 1241             new_data += self.read_channel_timing(read_timeout=20)
   1242             if new_data:
   1243                 return new_data

~/.local/share/virtualenvs/napalm-examples-yv4OVgxK/lib/python3.9/site-packages/netmiko/base_connection.py in read_channel_timing(self, last_read, read_timeout, delay_factor, max_loops)
    821
    822 """
--> 823             raise ReadTimeout(msg)
    824         return channel_data
    825

ReadTimeout:

read_channel_timing's absolute timer expired.

The network device was continually outputting data for longer than 20
seconds.

If this is expected i.e. the command you are executing is continually emitting
data for a long period of time, then you can set 'read_timeout=x' seconds. If
you want Netmiko to keep reading indefinitely (i.e. to only stop when there is
no new data), then you can set 'read_timeout=0'.

You can look at the Netmiko session_log or debug log for more information.

_test_channel_read() doesn't seem to find anything sent by the device, it seems to maybe have missed the prompt data from the previous command. If you skip running session_preparation you can successfully run commands on the device.

So in this change I'm sending an empty command to force the device to send the prompt again, and _test_channel_read will then succeed.

If this isn't the right way to handle this, or there's more information you'd like then let me know 😊

johanek commented 3 months ago

This didn't really fix my issue. The problem was with setting up the connection in the napalm driver.