just report missing config as nil in log

sharding isn't necessarily set up if this
fires during boot sequence

Change-Id: I2d5448184f141716bd38eb29beef33fe155abdb7
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/247927
Reviewed-by: Simon Williams <simon@instructure.com>
Reviewed-by: Jacob Burroughs <jburroughs@instructure.com>
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
QA-Review: Ethan Vizitei <evizitei@instructure.com>
Product-Review: Ethan Vizitei <evizitei@instructure.com>

lib/canvas/cache/fallback_expiration_cache.rb

@@ -16,7 +16,6 @@
 # with this program. If not, see <http://www.gnu.org/licenses/>.
 module Canvas
   module Cache
-    class NilCacheEntry < StandardError; end
     # all local cache implementations share a goal of being able to expire
     # cache entries before they're actually gone (think credentials expiring soon, etc),
     # but to hold onto the stale version just in case.
@@ -43,7 +42,6 @@ module Canvas
       def write_entry(key, entry, options)
         if entry.value.nil?
           Rails.logger.warn("[LOCAL_CACHE] Writing nil value for key #{key}")
-          Canvas::Errors.capture_exception(:local_cache, NilCacheEntry.new("No Config For Key: #{key}"))
         end
         super(key, entry, options)
         forever_entry = entry.dup

lib/canvas/dynamic_settings/prefix_proxy.rb

@@ -15,7 +15,6 @@
 # with this program. If not, see <http://www.gnu.org/licenses/>.
 module Canvas
   class DynamicSettings
-    class AbsentConfigError < StandardError; end
     # A class for reading values from Consul
     #
     # @attr prefix [String] The prefix to be prepended to keys for querying.
@@ -110,7 +109,6 @@ module Canvas
           return result if result
         end
         Rails.logger.warn("[DYNAMIC_SETTINGS] config requested which was found no-where (#{key})")
-        Canvas::Errors.capture_exception(:dynamic_settings, AbsentConfigError.new("No Config For Key: #{key}"))
         nil
       rescue Imperium::TimeoutError => exception
         LocalCache.fetch_without_expiration(CACHE_KEY_PREFIX + keys.first).tap do |val|

spec/lib/canvas/dynamic_settings/prefix_proxy_spec.rb

@@ -42,8 +42,6 @@ module Canvas
             .and_return(
               Imperium::Testing.kv_not_found_response(options: [:stale])
             )
-          allow(Canvas::Errors).to receive(:capture_exception).with(any_args).and_call_original
-          expect(Canvas::Errors).to receive(:capture_exception).with(:dynamic_settings, anything)
           expect(proxy.fetch('baz')).to be_nil
         end
 

spec/lib/local_cache_spec.rb

@@ -87,15 +87,5 @@ describe LocalCache do
       end
     end
 
-    it "allows writing nil, but will tell on you" do
-      expect(Canvas::Errors).to receive(:capture_exception) do |message, e|
-        expect(message).to eq(:local_cache)
-      end
-      LocalCache.fetch("never_seen_key") do
-        # nil on purpose
-        nil
-      end
-      expect(LocalCache.read("never_seen_key")).to be_nil
-    end
   end
 end