Core: Non-responsive sensor can block startup

[usul27]

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Home Assistant release (hass --version): 0.22

Python release (python3 --version): 3.4.2

Component/platform: Linux/RPi

Description of problem: A non-responsive sensor can block the startup

Expected:

Problem-relevant configuration.yaml entries and steps to reproduce:

switch:
  platform: edimax
  host: xxx
  username: admin
  password: xxx
  name: xxx

I use Home Assistant to control some Edimax switches. One of them became unresponsive. This completely blocked Home Assistant. Even restarting did not work as Home Assistant was hanging in the startup process waiting for a response from the Switch.

In general, reading data from sensors should be non-blocking. A single non-responsive component should not be able to block the whole startup. I don't think this is an issue specific to the Edimax platform, but a general issue that should be solved in the core.

[fabaff]

https://github.com/rkabadi/pyedimax/issues/1

[usul27]

While it may be a bug in a dependency, I think, HA should not allow an external library to block core functionalities. There should be at least some timeout mechanism that disables a plugin if it doesn't respond.

[fabaff]

Reference: #1543

[balloob]

Python does not have a good way of doing this for threaded solutions. Using async it would be possible but that's a core change we can't do. If you know of something please let us know

[usul27]

I understand that this isn't a thing to fix with a few lines of code. However, I think in the long run there need to be a change in the core to allow subsystems to work asynchronously. Otherwise problems like this will happen in many complex installations - especially when using external libraries that do not behave well. Blocking I/O is still the default in many libraries.

[Zac-HD]

@balloob - I think this one has been solved by the move to async core. Time to close the issue?

[balloob]

It actually has not been resolved. We still don't have implemented the timeout mentioned here but being async, it is possible.

[balloobbot]

There hasn't been any activity on this issue recently. Due to the high number of incoming GitHub notifications, we have to clean some of the old issues, as many of them have already been resolved with the latest updates.

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