allow configuring the default service tree for consul

Change-Id: Ic14fd4cf7326a88e5199e4ee1c0fb71a7d7598d0
Reviewed-on: https://gerrit.instructure.com/165386
Tested-by: Jenkins
Reviewed-by: James Williams  <jamesw@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>

lib/canvas/dynamic_settings.rb

@@ -50,9 +50,11 @@ module Canvas
           @environment = conf_hash['environment']
           @kv_client = Imperium::KV.default_client
           @data_center = conf_hash.fetch('global_dc', nil)
+          @default_service = conf_hash.fetch('service', :canvas)
         else
           @environment = nil
           @kv_client = nil
+          @default_service = :canvas
         end
       end
 
@@ -90,11 +92,12 @@ module Canvas
       # @param data_center [String] location of the data_center the proxy is pointing to
       def find( prefix = nil,
                 tree: :config,
-                service: :canvas,
+                service: nil,
                 cluster: nil,
                 default_ttl: DynamicSettings::PrefixProxy::DEFAULT_TTL,
                 data_center: nil
               )
+        service ||= @default_service || :canvas
         if kv_client
           PrefixProxy.new(
             prefix,

spec/initializers/consul_initializer_spec.rb

@@ -55,10 +55,10 @@ describe ConsulInitializer do
   describe "just from loading" do
     it "clears the DynamicSettings cache on reload" do
       Canvas::DynamicSettings.reset_cache!
-      Canvas::DynamicSettings::Cache.insert('key', 'value')
+      Canvas::DynamicSettings::Cache.insert('service/key', 'value')
       imperium = double('imperium', get: nil)
       allow(Canvas::DynamicSettings).to receive(:kv_client).and_return(imperium)
-      expect(Canvas::DynamicSettings.find(tree: nil, service: nil)['key']).to eq("value")
+      expect(Canvas::DynamicSettings.find(tree: nil, service: 'service')['key']).to eq("value")
       Canvas::Reloader.reload!
       expect(Canvas::DynamicSettings::Cache.store).to eq({})
     end