Only check for solr alias changes on a timer

The implementation of `solr_cloud-connection` is purposefully chatty, not caching anything because during the admin cycle, you want to see your changes reflected immediatley and the number of operations is generally small.

My use of uncached values (checking the name of the collection underlying an alias) on what turned out to be basically every call was disastrous.

This PR creates an instance of [Concurrent::TimerTask](https://ruby-concurrency.github.io/concurrent-ruby/master/Concurrent/TimerTask.html) that runs the check,
 and updates if needed, every 20 seconds.

 Notable changes are:
   * All the logic about updates is moved into `config/initializers/solr_admin_cache.rb`
   * The formerly-recursive method of determining the underlying collection
     name (because it's legal, in general, to have aliass that point to other
     aliases) has been removed, since we just don't need it.
   * The cached values are stored in `Concurrent::Atom` instances in
     the Services module with everything else
   * `load_local_config.rb` basically just calls `#value` on the
     Services values.
   * The footer now shows, ridiculously, the time down to the second.
     This is purely to make testing easier, because seeing a change in
     the footer date is an easy way to know the change has been made.

Gemfile

@@ -21,6 +21,8 @@ gem "aws-sdk-s3", "~> 1.160"
 gem "content_disposition", "~> 1.0"
 gem "uppy-s3_multipart", "~> 1.2"
 
+gem "concurrent-ruby"
+
 # CORS
 gem 'rack-cors'
 

Gemfile.lock

@@ -455,6 +455,7 @@ DEPENDENCIES
   bundler (~> 2.4.22)
   canister
   coffee-rails (~> 4.2)
+  concurrent-ruby
   content_disposition (~> 1.0)
   date_named_file
   debase

app/views/shared/_footer.html.erb

@@ -39,7 +39,7 @@
       Data last refreshed <%= if Dromedary::Services[:looks_like_first_upload]
                                 "never"
                               else
-                                Dromedary.collection_creation_date.strftime("%A, %B %-e, %Y")
+                                Dromedary.collection_creation_date_string
                               end
     %>.
     </p>

config/initializers/solr_admin_cache.rb

@@ -0,0 +1,35 @@
+S = Dromedary::Services
+
+# Set up some places to work
+S.register(:hyp_to_bibid) { Concurrent::Atom.new(:no_hyp_to_bib_id_yet) }
+S.register(:collection_creation_date) { Concurrent::Atom.new(:no_creation_date_yet) }
+S.register(:underlying_collection_name) {Concurrent::Atom.new(:no_underlying_name_yet) }
+
+
+# Update the underlying concurrent variables.
+# If the collection name underlying the (presumed) alias we're working with changes,
+# update the collection-specific data and reset our understanding of the
+# current collection name.
+def update_timeout_variables
+  Rails.logger.warn "################# CHECK FOR UPDATE ########################"
+  collection = S[:solr_current_collection]
+  actual_current_underlying_collection_name = collection.collection.name
+  expected_underlying_collection_name = S[:underlying_collection_name].value
+  if actual_current_underlying_collection_name != expected_underlying_collection_name
+    Rails.logger.warn "################# PERFORMING UPDATE ########################"
+    S[:hyp_to_bibid].reset MedInstaller::HypToBibId.get_from_solr(collection: collection)
+    S[:collection_creation_date].reset Dromedary.compute_collection_creation_date(actual_current_underlying_collection_name)
+    S[:underlying_collection_name].reset actual_current_underlying_collection_name
+  end
+end
+
+# The timer, with `run_now`, is supposed to run immediately, but I keep getting not-set-yet
+# errors, so we'll run it once manually on startup.
+update_timeout_variables
+
+# Run the update method ever 20 seconds
+collection_timer = Concurrent::TimerTask.new(execution_interval: 20, run_now: true) do
+  update_timeout_variables
+end
+# Need to call #execute to actually fire up the timer
+collection_timer.execute

config/load_local_config.rb

@@ -7,7 +7,7 @@
 module Dromedary
   class << self
     def logger
-      MedInstaller::Logger::LOGGER
+      Rails.logger || MedInstaller::Logger::LOGGER
     end
 
     # For whatever historical reasons, this uses the Ettin gem to load
@@ -26,34 +26,23 @@ def config
         ENV["RAILS_ENV"]
       else
         "development"
-      end
+            end
       @config = Dromedary::Services
     end
 
-    def hyp_to_bibid(collection: Dromedary::Services[:solr_current_collection])
-      logger.info "Trying to get hyp_to_bibid for collection #{collection}"
-      current_real_collection_name = underlying_real_collection_name(coll: collection)
-      logger.info "Real collection name identified as #{current_real_collection_name}"
-      if @recorded_real_collection_name != current_real_collection_name
-        @hyp_to_bibid = MedInstaller::HypToBibId.get_from_solr(collection: collection)
-        @recorded_real_collection_name = current_real_collection_name
-        @collection_creation_date = nil
-      end
-      @hyp_to_bibid
 
-    end
 
-    # @param coll [SolrCloud::Alias]
-    def underlying_real_collection_name(coll:  Dromedary::Services[:solr_current_collection])
-      return coll.name unless coll.alias?
-      underlying_real_collection_name(coll: coll.collection)
+    def hyp_to_bibid
+      Dromedary::Services[:hyp_to_bibid].value
     end
 
-    def collection_creation_date(coll:  Dromedary::Services[:solr_current_collection])
-      return @collection_creation_date if defined?(@collection_creation_date) && !@collection_creation_date.nil?
 
-      real_collection_name = underlying_real_collection_name(coll: coll)
-      @collection_creation_date = compute_collection_creation_date(real_collection_name)
+    def collection_creation_date
+      Dromedary::Services[:collection_creation_date].value
+    end
+
+    def collection_creation_date_string
+      collection_creation_date.strftime("%A, %B %-e, %Y at %H:%M:%S")
     end
 
     def compute_collection_creation_date(coll)

indexer/main_indexing_rules.rb

@@ -19,7 +19,7 @@
   provide "solr_writer.basic_auth_password", Dromedary::Services[:solr_password]
 end
 
-hyp_to_bibid = Dromedary.hyp_to_bibid(collection: Dromedary::Services[:solr_collection_to_index_into])
+hyp_to_bibid = MedInstaller::HypToBibId.get_from_solr(collection:  Dromedary::Services[:solr_collection_to_index_into])
 bibset = MiddleEnglishDictionary::Collection::BibSet.new(filename: settings["bibfile"])
 
 # Do a terrible disservice to traject and monkeypatch it to take