Add Sidekiq middleware to clear the ActiveRecord connection pool (issue

#16).

config/sidekiq.rb

@@ -2,12 +2,18 @@
 require 'sidekiq'
 require 'redis/namespace'
 
+require_relative '../lib/middleware/sidekiq/active_record_connection_pool'
+
 redis_config = {
   url: "redis://#{ENV['REDIS_HOST']}:#{ENV['REDIS_PORT']}"
 }
 
 Sidekiq.configure_server do |config|
   config.redis = redis_config
+
+  config.server_middleware do |chain|
+    chain.add Middleware::Sidekiq::ActiveRecordConnectionPool
+  end
 end
 
 Sidekiq.configure_client do |config|

lib/middleware/sidekiq/active_record_connection_pool.rb

@@ -0,0 +1,47 @@
+# frozen_string_literal: true
+#
+# ronin-app - a local web app for Ronin.
+#
+# Copyright (C) 2023 Hal Brodigan (postmodern.mod3@gmail.com)
+#
+# ronin-app is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# ronin-app is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with ronin-app.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+require 'active_record'
+
+module Middleware
+  module Sidekiq
+    #
+    # Sidekiq middleware to clear the ActiveRecord connection pool after each
+    # job.
+    #
+    class ActiveRecordConnectionPool
+
+      #
+      # Allows the job to be processed, then clears the ActiveRecord connection
+      # pool.
+      #
+      def call(*)
+        yield
+      ensure
+        begin
+          ActiveRecord::Base.connection_handler.clear_active_connections!
+        rescue => error
+          warn error.message
+        end
+      end
+
+    end
+  end
+end

spec/middleware/sidekiq/active_record_connection_pool_spec.rb

@@ -0,0 +1,46 @@
+require 'spec_helper'
+require 'middleware/sidekiq/active_record_connection_pool'
+
+describe Middleware::Sidekiq::ActiveRecordConnectionPool do
+  describe "#call" do
+    let(:worker) { double('Worker') }
+    let(:job)    { double('job') }
+    let(:queue)  { double('queue') }
+
+    it "must yield then call ActiveRecord::Base.connection_handler.clear_active_connections!" do
+      expect(ActiveRecord::Base.connection_handler).to receive(:clear_active_connections!)
+
+      expect { |b|
+        subject.call(worker,job,queue,&b)
+      }.to yield_control
+    end
+
+    context "when the block raises an exception" do
+      let(:message)   { "error!" }
+      let(:exception) { RuntimeError.new(message) }
+
+      it "must still call ActiveRecord::Base.connection_handler.clear_active_connections!" do
+        expect(ActiveRecord::Base.connection_handler).to receive(:clear_active_connections!)
+
+        expect {
+          subject.call(worker,job,queue) do
+            raise(exception)
+          end
+        }.to raise_error(exception)
+      end
+    end
+
+    context "when ActiveRecord::Base.connection_handler.clear_active_connections! raises an exception" do
+      let(:message)   { "ActiveRecord error!" }
+      let(:exception) { RuntimeError.new(message) }
+
+      it "must print the error message to stderr" do
+        expect(ActiveRecord::Base.connection_handler).to receive(:clear_active_connections!).and_raise(exception)
+
+        expect { |b|
+          subject.call(worker,job,queue,&b)
+        }.to yield_control.and(output("#{message}#{$/}").to_stderr)
+      end
+    end
+  end
+end