延迟作业如何在 Ruby on Rails 中工作?

问题描述

我对此很陌生，对延迟作业的工作原理有点困惑?

我知道它会创建一个表并将作业放入表中，然后我需要运行

rake 工作:工作

启动后台进程.现在我的问题是

1. DJ 脚本是否每分钟检查一次表格，当时间与 job_at 时间匹配时，它会运行该作业吗?

2. 如果脚本只是每分钟检查一次表，它与 cron(每当 gem)有什么不同?

谢谢

解决方案

当您运行 rake jobs:work 时，DelayedJob 将轮询 delayed_jobs 表，执行与 job_at 列值(如果已设置)匹配的作业.这部分你是对的.

1. 如果脚本只是每分钟检查一次表，它与 cron(每当 gem)有什么不同?

whenever 是一个帮助你配置 crontab 的 gem.它与定期在服务器上执行任务没有任何直接关系.

您可以设置一个 cron 来每分钟运行队列中存在的任何任务，但是让 delayed_job 守护进程运行有多种好处.

• 即使 cron 每分钟运行一次，delayed_job 的守护进程也会看到并执行在 cron 运行之间的 1 分钟窗口内排队的任何作业
• 每次运行 cron 时，它都会重建一个新的 Rails 环境来执行作业.当守护程序可以立即坐在那里准备执行新排队的作业时，这是一种时间和资源的浪费.

如果您想每分钟通过一个 cron 配置 delayed_job，您可以将这样的内容添加到您的 crontab 中

* * * * * RAILS_ENV=生产脚本/delayed_job start --exit-on-complete

每分钟，delayed_job 都会启动，执行任何为它准备好的作业，或者它必须从先前失败的运行中重试，然后退出.虽然我不推荐这个.将 delay_job 设置为守护进程是正确的做法.

I am new to this and is little confused about how Delayed Job works ?

I know it creates a table and puts the jobs in the table and then I need to run

rake jobs:work

to start the background process. Now my question is

1. Does DJ script checks the table every minute and when the time matches job_at time, it runs that job ?

2. How it is different than cron (whenever gem) if the script is just checking the table every min ?

Thanks

解决方案

When you run rake jobs:work DelayedJob will poll the delayed_jobs table, performing jobs matching the job_at column value if it's been set. This part you're correct about.

whenever is a gem that helps you configure a crontab. It has nothing directly to do with performing tasks on your server on a periodic basis.

You could setup a cron to run whatever tasks exist in the queue every minute, but leaving a delayed_job daemon running has multiple benefits.

• Even if the cron ran every minute, delayed_job's daemon will see and perform any jobs queued within that 1-minute window between cron runs
• Every time the cron would run, it will rebuild a new Rails environment in which to perform the jobs. This is a waste of time and resources when the daemon can just sit there immediately ready to perform a newly queued job.

If you want to configure delayed_job through a cron every minute you can add something like this to your crontab

* * * * * RAILS_ENV=production script/delayed_job start --exit-on-complete

Every minute, delayed_job will spin up, perform whatever jobs are ready for it or which it must retry from a previously failed run, and then quit. I don't recommend this though. Setting up a delayed_job as a daemon is the right way to go.

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