refs https://github.com/TryGhost/Ghost/issues/12496
- `workerMessageHandler` option allows for custom worker message handling and allows to eliminate a need for loggers of any type inside of jobs.
- removing loggers from jobs solves file hanle leak which used to cause Ghost process to crash (see referenced issue)
refs #122
- In future changes there's a plan to add "inline" scheduled jobs, which would conflict current method naming.
- The amount of parameters in the methods was more than 3, so it made sense to transform them into an options object
- Scheduling still doesn't work for "inline" jobs. This should be solved as a part of upstream library (https://github.com/breejs/bree/issues/68)
closes https://github.com/TryGhost/Ghost-Utils/issues/118
- Custom error handling is needed to be able to override default bree
error handling logic.
- bree bump to 4.1.0 also fixed logging errors (object Object fix in
tests)
- The handler function receives two parameters. First contains an error
that has been thrown by the job. Second, job and worker metadata
closes#117
- Having immediately executable offloaded jobs is necessary to be able to run usecases like: send batched emails now, or any other job that does not need to be scheduled
- Changed "simple" job timeout to make tests run faster
closes#119
- A future use-case which this feature caters for is allowing to migrate "post scheduler" to use job manager instead of managing scheduling itself
- removeJob method will be needed to allow "rescheduling" of the post
no issue
- When providing a crontab schedule expression it should always contain 6 elements first one of them being a "seconds" schedule description . For example: '0/5 * * * * *' - meaning to run every 5 seconds
no issue
- When jobs are performing CPU intensive tasks they block main process'
event loop. They also can cause memory leaks or unexpected crashes
effectively crashing the parent proccess. To address these issues jobs need to be performed off of main
process. Worker Threads (https://nodejs.org/dist/latest-v12.x/docs/api/worker_threads.html)
are the best candidate for such work.
- These changes introduce an integration on top of bree
(https://github.com/breejs/bree/) which allows to run recurring
jobs in worker thereads. It falls back to child process execution for
Node v10 running without `--experimental-worker` flag.
- bree was chosen not only because it gives a polyfill for older Node
versions. It has support for some of the future use-cases Ghost is looking to
implement, like scheduled jobs.
- This changeset also includes a complete example of job running on an
interval with a possibility for graceful shutdown
no issue
- This is a quick implementation change to prevent from queue stalling and never becoming idle in case there's an error thrown from within the job function/module
- More robust error handling should be designed soon!
no issue
- Jobs should not always be functions, one of the standard practices is having a job defined in a module as a self contained executable function
- First parameter of `addJob` function now also handles path to modules which it imports and executes
no issue
- Accepting the schedule or a data when scheduled job should be run would follow a signature used in other established frameworks: (1) https://github.com/mperham/sidekiq/wiki/Ent-Periodic-Jobs#definition
- Another reason to put scheduling parameter first is this would allow leaving an optional "data" parameter as last
no issue
- CRON format is the most common one used for job scheduling and is well known to most developers
- This will become one of supported formats for job scheduling
