simplify logic around if we should check the user's home shard for a …

…pseudonym first

fixes FOO-987

Change-Id: I46fdfabcc639d77b4cbad2fae50a0fd52667d30d
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/249478
Reviewed-by: Simon Williams <simon@instructure.com>
Reviewed-by: Jacob Burroughs <jburroughs@instructure.com>
Reviewed-by: Ethan Vizitei <evizitei@instructure.com>
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>

app/models/sis_pseudonym.rb

@@ -75,8 +75,10 @@ def find_in_other_accounts
 
     trusted_account_ids = root_account.trusted_account_ids.group_by { |id| Shard.shard_for(id) } if type == :trusted
 
-    # try the user's home shard first
-    unless @in_region && (!user.shard.in_current_region? || !user.shard.default?)
+    # try the user's home shard first if it's fast
+    # the default shard has a replica in every region, so is always fast
+    user_shard_is_in_region = user.shard.in_current_region? || user.shard.default?
+    if user_shard_is_in_region
       if type != :trusted || (account_ids = trusted_account_ids[user.shard])
         user.shard.activate do
           result = find_in_trusted_accounts(account_ids)
@@ -92,7 +94,7 @@ def find_in_other_accounts
     return nil if shards.empty?
 
     Shard.with_each_shard(shards.sort) do
-      next if Shard.current == user.shard
+      next if Shard.current == user.shard && user_shard_is_in_region
       account_ids = trusted_account_ids[Shard.current] if type == :trusted
       result = find_in_trusted_accounts(account_ids)
       return result if result

spec/models/sis_pseudonym_spec.rb

@@ -234,6 +234,19 @@ def pseud_params(unique_id, account = Account.default)
         expect(SisPseudonym.for(@user, Account.default)).to eq @pseudonym
       end
     end
+
+    it "looks in other accounts" do
+      @shard1.activate do
+        @s1root = account_model
+        @user = User.create!
+        @pseudonym = @s1root.pseudonyms.create!(user: @user, unique_id: 'user') do |p|
+          p.sis_user_id = 'abc'
+        end
+        allow_any_instantiation_of(@pseudonym).to receive(:works_for_account?).with(Account.default, true).and_return(true)
+      end
+      expect(SisPseudonym.for(@user, Account.default, type: :implicit)).to eq @pseudonym
+      expect(SisPseudonym.for(@user, Account.default, type: :implicit, in_region: true)).to eq @pseudonym
+    end
   end
 
 end