Class: OnlineMigrations::BackgroundSchemaMigrations::MigrationRunner

Inherits:
Object
  • Object
show all
Defined in:
lib/online_migrations/background_schema_migrations/migration_runner.rb

Overview

Runs single background schema migration.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(migration) ⇒ MigrationRunner

Returns a new instance of MigrationRunner.



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# File 'lib/online_migrations/background_schema_migrations/migration_runner.rb', line 9

def initialize(migration)
  @migration = migration
end

Instance Attribute Details

#migration ⇒ Object (readonly)

Returns the value of attribute migration.



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# File 'lib/online_migrations/background_schema_migrations/migration_runner.rb', line 7

def migration
  @migration
end

Instance Method Details

#run ⇒ Object 



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# File 'lib/online_migrations/background_schema_migrations/migration_runner.rb', line 13

def run
  return if migration.cancelled? || migration.succeeded?

  migration.running! if migration.enqueued? || migration.errored?
  migration_payload = { migration: migration }

  if migration.attempts == 0
    ActiveSupport::Notifications.instrument("started.background_schema_migrations", migration_payload)
  else
    ActiveSupport::Notifications.instrument("retried.background_schema_migrations", migration_payload)
  end

  if should_throttle?
    ActiveSupport::Notifications.instrument("throttled.background_schema_migrations", migration_payload)
    return
  end

  migration.update!(
    attempts: migration.attempts + 1,
    status: :running,
    started_at: Time.current,
    finished_at: nil,
    error_class: nil,
    error_message: nil,
    backtrace: nil
  )

  ActiveSupport::Notifications.instrument("run.background_schema_migrations", migration_payload) do
    migration.run
  end

  # Background schema migrations could take a while to run. It is possible, that the process
  # never reaches this (or the rescue below) line of code. E.g., when it is force quitted
  # (SIGKILL etc.) and so the migration will end up in the "running" state and the query is
  # still executing (or already finished) in the database. This migration can either be safely
  # manually retried or will be picked up in the future by scheduler when it decides that
  # this migration is stuck.

  migration.update!(status: :succeeded, finished_at: Time.current)

  ActiveSupport::Notifications.instrument("completed.background_schema_migrations", migration_payload)
rescue Exception => e # rubocop:disable Lint/RescueException
  backtrace_cleaner = ::OnlineMigrations.config.backtrace_cleaner

  status = migration.attempts_exceeded? ? :failed : :errored

  migration.update!(
    status: status,
    finished_at: Time.current,
    error_class: e.class.name,
    error_message: e.message,
    backtrace: backtrace_cleaner ? backtrace_cleaner.clean(e.backtrace) : e.backtrace
  )

  ::OnlineMigrations.config.background_schema_migrations.error_handler.call(e, migration)
  raise if Utils.run_background_migrations_inline?
end