Rails的确切作业执行顺序delay_job

Question

我正在使用Collectoridea的delay_job版本：https : //github.com/collectiveidea/delayed_job

谁能指出我当工人去选择下一份工作时所使用的实际标准？我假设它像“ SELECT ID FROM Delayed_jobs WHERE run_at> NOW（）ORDER BY priority ASC，run_at ASC LIMIT 1”（优先选择优先，run_at时间第二），但我一直无法找到确切的内容考虑过的。我已经在GitHub上的代码中做了一些探索，但是还没有找到下一份工作的实际查询。对几件事感到好奇，包括是否将“ created_at”，“ attempts”或“ failed_at”因素都放在了优先级中。（而且我意识到我不太可能找到实际的SQL，这只是表示我假设查询所做的一种简单方法）。

其次，该宝石的实际文档有什么好的来源？对于在Rails中如此普遍使用的东西，我所看到的文档相当稀疏。

Answer 1

有点挖掘源代码可以在backend / active_record.rb中看到：

    scope :ready_to_run, lambda {|worker_name, max_run_time|
      where(['(run_at <= ? AND (locked_at IS NULL OR locked_at < ?) OR locked_by = ?) AND failed_at IS NULL', db_time_now, db_time_now - max_run_time, worker_name])
    }
    scope :by_priority, order('priority ASC, run_at ASC')

    # Find a few candidate jobs to run (in case some immediately get locked by others).
    def self.find_available(worker_name, limit = 5, max_run_time = Worker.max_run_time)
      scope = self.ready_to_run(worker_name, max_run_time)
      scope = scope.scoped(:conditions => ['priority >= ?', Worker.min_priority]) if Worker.min_priority
      scope = scope.scoped(:conditions => ['priority <= ?', Worker.max_priority]) if Worker.max_priority

      ::ActiveRecord::Base.silence do
        scope.by_priority.all(:limit => limit)
      end
    end

同样，backend / base.rb中的这一位很有趣：

    def reserve(worker, max_run_time = Worker.max_run_time)
      # We get up to 5 jobs from the db. In case we cannot get exclusive access to a job we try the next.
      # this leads to a more even distribution of jobs across the worker processes
      find_available(worker.name, 5, max_run_time).detect do |job|
        job.lock_exclusively!(max_run_time, worker.name)
      end
    end

reserve 由工人叫来选择下一份工作。