Sensu config.json cannot be left blank

/opt/sensu/embedded/lib/ruby/gems/2.3.0/gems/sensu-settings-3.4.0/lib/sensu/settings/loader.rb:292:in `deep_merge': undefined method `each' for nil:NilClass (NoMethodError)
from /opt/sensu/embedded/lib/ruby/gems/2.3.0/gems/sensu-settings-3.4.0/lib/sensu/settings/loader.rb:96:in `load_file'
from /opt/sensu/embedded/lib/ruby/gems/2.3.0/gems/sensu-settings-3.4.0/lib/sensu/settings.rb:17:in `load'
from /opt/sensu/embedded/lib/ruby/gems/2.3.0/gems/sensu-settings-3.4.0/lib/sensu/settings.rb:38:in `get'
from /opt/sensu/embedded/lib/ruby/gems/2.3.0/gems/sensu-0.23.2/lib/sensu/daemon.rb:104:in `load_settings'
from /opt/sensu/embedded/lib/ruby/gems/2.3.0/gems/sensu-0.23.2/lib/sensu/daemon.rb:50:in `initialize'
from /opt/sensu/embedded/lib/ruby/gems/2.3.0/gems/sensu-0.23.2/lib/sensu/server/process.rb:40:in `initialize'
from /opt/sensu/embedded/lib/ruby/gems/2.3.0/gems/sensu-0.23.2/lib/sensu/server/process.rb:28:in `new'
from /opt/sensu/embedded/lib/ruby/gems/2.3.0/gems/sensu-0.23.2/lib/sensu/server/process.rb:28:in `run'
from /opt/sensu/embedded/lib/ruby/gems/2.3.0/gems/sensu-0.23.2/exe/sensu-server:10:in `'
from /opt/sensu/bin/sensu-server:22:in `load'
from /opt/sensu/bin/sensu-server:22:in `'


That's what it looks like when you put all your configuration information for sensu into /etc/sensu/conf.d and leave /etc/sensu/config.json empty.

To solve, you can just put the following into /etc/sensu/config.json and sensu will happily do a deep merge with your other files:

{
}


For more on how Sensu starts up, see Sensu Configuration Reference documentation.