Add database_connection_pool stats to GoodJob::Process.current_state

[dixpac]

This commit adds snapshot of database connection pool to a GoodJob::Process.current_state method.

• size - Total capacity of connection pool
• active - Number of connections in the pool that are in_use/active

References #1014

[dixpac]

Tried to write a test, but it ended up in a large number of stubs, so I'm not sure will it be valuable and stable.

RSpec.describe GoodJob::Process do
  describe '.current_state' do
    before do
      allow(SecureRandom).to receive(:uuid).and_return("test-uuid")
      allow(Socket).to receive(:gethostname).and_return("test-hostname")
      allow(::Process).to receive(:pid).and_return(1234)

     scheduler_instance = instance_double(
       GoodJob::Scheduler,
       stats: { succeeded_executions_count: 10, errored_executions_count: 5 },
       shutdown: nil, 
       shutdown?: true 
      )

      allow(GoodJob::Scheduler).to receive(:instances).and_return([scheduler_instance])


      allow(GoodJob).to receive(:preserve_job_records).and_return(true)
      allow(GoodJob).to receive(:retry_on_unhandled_error).and_return(false)
      allow(GoodJob).to receive_message_chain(:configuration, :enable_cron?).and_return(true)

      connection_pool = instance_double(ActiveRecord::ConnectionAdapters::ConnectionPool, size: 10, connections: [instance_double(ActiveRecord::ConnectionAdapters::AbstractAdapter, in_use?: true)] * 5)
      allow(ActiveRecord::Base).to receive(:connection_pool).and_return(connection_pool)
    end

    it 'returns the correct state' do
      state = GoodJob::Process.current_state

      expect(state).to eq({
        id: "test-uuid",
        hostname: "test-hostname",
        pid: 1234,
        proctitle: $PROGRAM_NAME,
        preserve_job_records: true,
        retry_on_unhandled_error: false,
        schedulers: [{ succeeded_executions_count: 10, errored_executions_count: 5 }],
        cron_enabled: true,
        total_succeeded_executions_count: 10,
        total_errored_executions_count: 5,
        connection_pool: { 
          size: 10,
          active: 5
        }
      })
    end
  end
end

[bensheldon]

This is great! Thank you 🎉

I tweaked the name and added a minimal "doesn't blow up"-style test.