Deadlock when threads < number of event hubs + 1

[jakelandis]

If you configure multiple events without changing the thread configuration, this plugin can deadlock. The plugin requires the usage of least 2 threads (hard coded), and is the result of observation of the underlying library when reading a single event hub.

The default min number of threads needs to be changed from default of 4 with a hard coded min of 2, to a default and min = the number of configured event hubs + 1. For example, if you are reading 7 event hubs, you will need 8 threads.

This bug only effects when reading from 3 or more event hubs without changing the default threads. The work around is to specify the threads configuration option to ensure it is equal to or greater then event hubs + 1.

[redNixon]

The default min number of threads needs to be changed from default of 4 with a hard coded min of 2

I can confirm that 1 thread should be kicked out as a config error and will cause logstash to go silent without throwing any errors that point to any issue or the cause.