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We don’t currently really have “infrastructure-as-a-service” with our heroku setup, it’s just set up on the heroku system (and third-party systems) via GUI and/or CLI’s, there isn’t any kind of script to recreate our heroku setup from nothing.

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• Delete all failed jobs in the rescue admin pages.

• Make a rake task to enqueue all the jobs to the special_jobs queue.

  • The task should be smart enough to skip items that have already been processed. That way, you can interrupt the task at any time, fix any problems, and run it again later without having to worry.

  • Make sure you have an easy way to run the task on individual items manually from the admin pages or the console.

  • The job that the task calls should print the IDs of any entities it’s working on to the Heroku logs.

  • It’s very helpful to be able to enqueue a limited number of items and run them first, before embarking on the full run. For instance you could add an extra boolean argument only_do_10 (defaulting to false ) and add a variation on:

    Code Block
    scope = scope[1..10] if only_do_10

• Test the rake task in staging with only_do_10 set to true.

• Run the rake task in production but only_do_10 for a trial run.

• Spin up a single special_jobs dyno and watch it process 10 items.

• Run the rake task in production.

• The jobs are now in the special_jobs queue, but no work will actually start until you spin up dedicated dynos.

• 2 workers per special_jobs dyno is our default, which works nicely with standard-2x dynos, but if you want, try setting SPECIAL_JOB_WORKER_COUNT env variable to 3.

• Max special_jobs dynos will be limited by the smaller of max postgres connections and max redis connections, including connections in use by web workers. Currently we have 500 max redis connections, and 120 max postgres connections. You may want to monitor the redis statistics during the job.

• Manually spin up a set of special_worker dynos of whatever type you want at Heroku's "resources" page for the application. Heroku will alert you to the cost. (10 standard-2x dynos cost roughly $1 per hour, for instance; with the worker count set to two, you’ll see up to 20 items being processed simultaneously).

• Monitor the progress of the resulting workers. Work goes much faster than you are used to, so pay careful attention to:

  • the Papertrail logs

  • the resque pages of the app

  • the redis statistics for the app in Heroku (go to the resource page then click “Heroku data for redis”.

• If there are errors in any of the jobs, you can retry the jobs in the Rescue pages, or rerun them from the console.

• Monitor the number of jobs still pending in the special_jobs queue. When that number goes to zero, it means the work will complete soon and you should start getting ready to turn off the dynos. It does NOT mean the work is complete, however!

• When all the workers in the special_jobs queue complete their jobs and are idle:

  • rake scihist:resque:prune_expired_workers will get rid of any expired workers, if needed

  • Set the number of special_workerdynos back to zero.

  • Remove the special_jobs queue from the resque pages.

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Heroku has a list of key/values that are provided to app, called “config vars”. They can be seen and set in the Web GUI under the settings tab, or via the heroku command line heroku config, heroku config:set, heroku config:get etc.

• We need to disable the heroku nodejs buildpack from “pruning development dependencies”, because our rails setup needs our dev dependencies (such as vite) at asset:precompile time, at which they would otherwise be gone. See vite-ruby docs and heroku docs. To do this we set config:set YARN_PRODUCTION=false

Note:

• Some config variables are set by heroku itself/heroku add-ons, such as DATABASE_URL (set by postgres add-on). They should not be edited manually. Unfortunately there is no completely clear documentation of which is which.

• Some config variables include sensitive information such as passwords. If you do a heroku config to list them all, you should be careful where you put/store them, if anywhere.

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