Add a connection to the pool if there is only one in the EmbeddedAnsi…

…ble worker

Before ManageIQ#6786 we used to
have one connection specified in the connection pool in database.yml

Installations which have been upgraded from before this change
still have that one connection pool in place.

The EmbeddedAnsible worker uses a thread rather than a new process
so it shares the connection pool with the server. When the pool
is set to only contain one connection, the EmbeddedAnsible worker
will not be able to start.

This commit adds a connection to the pool in the same way that we do
for workers which specify a specific connection pool size in their settings:
https://github.com/ManageIQ/manageiq/blob/f6f7120749d16fd7825f83001dfd875cdecb903c/app/models/miq_worker/runner.rb#L71-L78

https://bugzilla.redhat.com/show_bug.cgi?id=1484150

app/models/embedded_ansible_worker.rb

@@ -13,6 +13,8 @@ def start_runner
   end
 
   def start_monitor_thread
+    fix_connection_pool
+
     t = Thread.new do
       begin
         self.class::Runner.start_worker(worker_options)
@@ -58,4 +60,13 @@ def status_update
 
   # Base class methods we override since we don't have a separate process.  We might want to make these opt-in features in the base class that this subclass can choose to opt-out.
   def release_db_connection; end
+
+  private
+
+  def fix_connection_pool
+    # If we only have one connection in the pool, it will be being used by the server
+    # Add another so we can start the worker thread
+    current = ActiveRecord::Base.connection_pool.instance_variable_get(:@size)
+    ActiveRecord::Base.connection_pool.instance_variable_set(:@size, 2) if current == 1
+  end
 end

spec/models/embedded_ansible_worker_spec.rb

@@ -136,13 +136,26 @@
     end
 
     describe "#start_monitor_thread" do
-      it "sets worker class and id in thread object" do
+      let(:pool) { double("ConnectionPool") }
+
+      before do
         allow(Thread).to receive(:new).and_return({})
         allow(described_class::Runner).to receive(:start_worker)
+      end
+
+      it "sets worker class and id in thread object" do
         thread = subject.start_monitor_thread
         expect(thread[:worker_class]).to eq subject.class.name
         expect(thread[:worker_id]).to    eq subject.id
       end
+
+      it "adds a connection to the pool if there is only one" do
+        allow(ActiveRecord::Base).to receive(:connection_pool).and_return(pool)
+
+        expect(pool).to receive(:instance_variable_get).with(:@size).and_return(1)
+        expect(pool).to receive(:instance_variable_set).with(:@size, 2)
+        subject.start_monitor_thread
+      end
     end
 
     describe "#find_worker_thread_object" do