Trigger iid logic from GitHub importer for issues.

lib/gitlab/github_import/importer/issue_importer.rb

@@ -55,7 +55,11 @@ module Gitlab
             updated_at: issue.updated_at
           }
 
-          GithubImport.insert_and_return_id(attributes, project.issues)
+          GithubImport.insert_and_return_id(attributes, project.issues).tap do |id|
+            # We use .insert_and_return_id which effectively disables all callbacks.
+            # Trigger iid logic here to make sure we track internal id values consistently.
+            project.issues.find(id).ensure_project_iid!
+          end
         rescue ActiveRecord::InvalidForeignKey
           # It's possible the project has been deleted since scheduling this
           # job. In this case we'll just skip creating the issue.

spec/lib/gitlab/github_import/importer/issue_importer_spec.rb

@@ -78,6 +78,11 @@ describe Gitlab::GithubImport::Importer::IssueImporter, :clean_gitlab_redis_cach
         .to receive(:id_for)
         .with(issue)
         .and_return(milestone.id)
+
+      allow(importer.user_finder)
+        .to receive(:author_id_for)
+        .with(issue)
+        .and_return([user.id, true])
     end
 
     context 'when the issue author could be found' do
@@ -172,6 +177,23 @@ describe Gitlab::GithubImport::Importer::IssueImporter, :clean_gitlab_redis_cach
 
       expect(importer.create_issue).to be_a_kind_of(Numeric)
     end
+
+    it 'triggers internal_id functionality to track greatest iids' do
+      allow(importer.user_finder)
+        .to receive(:author_id_for)
+        .with(issue)
+        .and_return([user.id, true])
+
+      issue = build_stubbed(:issue, project: project)
+      allow(Gitlab::GithubImport)
+        .to receive(:insert_and_return_id)
+        .and_return(issue.id)
+      allow(project.issues).to receive(:find).with(issue.id).and_return(issue)
+
+      expect(issue).to receive(:ensure_project_iid!)
+
+      importer.create_issue
+    end
   end
 
   describe '#create_assignees' do