Class: OnlineMigrations::BackgroundDataMigrations::Migration

Inherits:
ApplicationRecord
  • Object
show all
Includes:
ShardAware
Defined in:
lib/online_migrations/background_data_migrations/migration.rb

Overview

Note:

The records of this class should not be created manually, but via enqueue_background_data_migration helper inside migrations.

Class representing background data migration.

Constant Summary collapse

STATUSES = 
[
  "pending",     # The migration has been created by the user.
  "enqueued",    # The migration has been enqueued by the scheduler.
  "running",     # The migration is being performed by a migration executor.
  "pausing",     # The migration has been told to pause but is finishing work.
  "paused",      # The migration was paused in the middle of the run by the user.
  "errored",     # The migration raised an error during last run.
  "failed",      # The migration raises an error when running and retry attempts exceeded.
  "succeeded",   # The migration finished without error.
  "cancelling",  # The migration has been told to cancel but is finishing work.
  "cancelled",   # The migration was cancelled by the user.
  "delayed",     # The migration was created, but waiting approval from the user to start running.
]
COMPLETED_STATUSES = 
["succeeded", "failed", "cancelled"]
ACTIVE_STATUSES = 
[
  "pending",
  "enqueued",
  "running",
  "failed",
  "pausing",
  "paused",
  "cancelling",
]
STOPPING_STATUSES = 
["pausing", "cancelling", "cancelled"]

Class Method Summary collapse

Instance Method Summary collapse

Methods included from ShardAware

#connection_class, #connection_class_name=, #on_shard_if_present

Class Method Details

.normalize_migration_name(migration_name) ⇒ Object 



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# File 'lib/online_migrations/background_data_migrations/migration.rb', line 66

def self.normalize_migration_name(migration_name)
  namespace = ::OnlineMigrations.config.background_data_migrations.migrations_module
  migration_name.sub(/^(::)?#{namespace}::/, "")
end

Instance Method Details

#active? ⇒ Boolean

Returns whether the migration is active, which is defined as having a status of pending, enqueued, running, pausing, paused, or cancelling.

Returns:

  • (Boolean) —

    whether the migration is active.



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# File 'lib/online_migrations/background_data_migrations/migration.rb', line 107

def active?
  ACTIVE_STATUSES.include?(status)
end

#cancel ⇒ Boolean

Cancel this data migration. No-op if migration is completed.

Returns:

  • (Boolean) —

    whether this data migration was cancelled.



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# File 'lib/online_migrations/background_data_migrations/migration.rb', line 166

def cancel
  return false if completed?

  if paused? || delayed? || stuck?
    update!(status: :cancelled, finished_at: Time.current)
  elsif pending? || enqueued? || errored?
    cancelled!
  else
    cancelling!
  end

  true
end

#complete ⇒ Object 



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# File 'lib/online_migrations/background_data_migrations/migration.rb', line 227

def complete
  return false if completed?

  if running?
    update!(status: :succeeded, finished_at: Time.current)
    data_migration.after_complete
  elsif pausing?
    update!(status: :paused, finished_at: Time.current)
  elsif cancelling?
    update!(status: :cancelled, finished_at: Time.current)
    data_migration.after_complete
  end

  true
end

#completed? ⇒ Boolean

Returns whether the migration is completed, which is defined as having a status of succeeded, failed, or cancelled.

Returns:

  • (Boolean) —

    whether the migration is completed.



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# File 'lib/online_migrations/background_data_migrations/migration.rb', line 98

def completed?
  COMPLETED_STATUSES.include?(status)
end

#cursor ⇒ Object

TODO: delete in some future version



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# File 'lib/online_migrations/background_data_migrations/migration.rb', line 72

def cursor
  self[:cursor]
rescue JSON::ParserError
  cursor_before_type_cast
end

#data_migration ⇒ OnlineMigrations::DataMigration

Returns data migration associated with this migration.

Returns:



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# File 'lib/online_migrations/background_data_migrations/migration.rb', line 294

def data_migration
  @data_migration ||= begin
    klass = DataMigration.named(migration_name)
    klass.new(*arguments)
  end
end

#enqueue ⇒ Boolean

Enqueue this data migration. No-op if migration is not delayed.

Returns:

  • (Boolean) —

    whether this data migration was enqueued.



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# File 'lib/online_migrations/background_data_migrations/migration.rb', line 153

def enqueue
  if delayed?
    pending!
    true
  else
    false
  end
end

#migration_name=(class_name) ⇒ Object Also known as: name= 



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# File 'lib/online_migrations/background_data_migrations/migration.rb', line 78

def migration_name=(class_name)
  class_name = class_name.name if class_name.is_a?(Class)
  write_attribute(:migration_name, self.class.normalize_migration_name(class_name))
end

#pausable? ⇒ Boolean

Returns whether this migration is pausable.

Returns:

  • (Boolean) 


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# File 'lib/online_migrations/background_data_migrations/migration.rb', line 270

def pausable?
  true
end

#pause ⇒ Boolean

Pause this data migration. No-op if migration is completed.

Returns:

  • (Boolean) —

    whether this data migration was paused.



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# File 'lib/online_migrations/background_data_migrations/migration.rb', line 184

def pause
  return false if completed?

  if pending? || enqueued? || delayed? || stuck? || errored?
    paused!
  else
    pausing!
  end

  true
end

#persist_error(error, attempt) ⇒ Object 



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# File 'lib/online_migrations/background_data_migrations/migration.rb', line 253

def persist_error(error, attempt)
  backtrace = error.backtrace
  backtrace_cleaner = OnlineMigrations.config.backtrace_cleaner
  backtrace = backtrace_cleaner.clean(backtrace) if backtrace_cleaner
  status = attempt >= max_attempts ? :failed : :errored

  update!(
    status: status,
    finished_at: Time.current,
    error_class: error.class.name,
    error_message: error.message,
    backtrace: backtrace
  )
end

#persist_progress(cursor, number_of_ticks, duration) ⇒ Object 



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# File 'lib/online_migrations/background_data_migrations/migration.rb', line 244

def persist_progress(cursor, number_of_ticks, duration)
  update!(
    cursor: cursor,
    tick_count: tick_count + number_of_ticks,
    time_running: time_running + duration
  )
end

#progress ⇒ Float?

Returns the progress of the data migration.

Returns:

  • (Float, nil) —
    • when background migration is configured to not track progress, returns nil
    • otherwise returns value in range from 0.0 to 100.0


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# File 'lib/online_migrations/background_data_migrations/migration.rb', line 280

def progress
  if succeeded?
    100.0
  elsif tick_total == 0
    0.0
  elsif tick_total
    ([tick_count.to_f / tick_total, 1.0].min * 100)
  end
end

#resume ⇒ Boolean

Resume this data migration. No-op if migration is not paused.

Returns:

  • (Boolean) —

    whether this data migration was resumed.



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# File 'lib/online_migrations/background_data_migrations/migration.rb', line 200

def resume
  if paused?
    pending!
    true
  else
    false
  end
end

#retry ⇒ Object

Mark this migration as ready to be processed again.

This method marks failed migrations as ready to be processed again, and they will be picked up on the next Scheduler run.



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# File 'lib/online_migrations/background_data_migrations/migration.rb', line 306

def retry
  if failed?
    update!(
      status: :pending,
      started_at: nil,
      finished_at: nil,
      error_class: nil,
      error_message: nil,
      backtrace: nil,
      jid: nil
    )
    true
  else
    false
  end
end

#start ⇒ Object 



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# File 'lib/online_migrations/background_data_migrations/migration.rb', line 133

def start
  if enqueued?
    # Defer `tick_total` calculation to the migration starting time
    # instead of the enqueueing time to avoid failed deploys.
    self.tick_total ||= safely_calculate_tick_total
    self.status = :running
    self.started_at = Time.current
    save!

    data_migration.after_start
    true
  else
    false
  end
end

#started? ⇒ Boolean

Returns whether the migration has been started, which is indicated by the started_at timestamp being present.

Returns:

  • (Boolean) —

    whether the migration was started.



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# File 'lib/online_migrations/background_data_migrations/migration.rb', line 89

def started?
  started_at.present?
end

#stop ⇒ Object 



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# File 'lib/online_migrations/background_data_migrations/migration.rb', line 210

def stop
  return false if completed?

  if cancelling?
    update!(status: :cancelled, finished_at: Time.current)
    data_migration.after_cancel
    data_migration.after_complete
  elsif pausing?
    paused!
    data_migration.after_pause
  end

  data_migration.after_stop
  true
end

#stopping? ⇒ Boolean

Returns whether the migration is stopping, which is defined as having a status of pausing or cancelling. The status of cancelled is also considered stopping since a migration can be cancelled while its job still exists in the queue, and we want to handle it the same way as a cancelling run.

Returns:

  • (Boolean) —

    whether the migration is stopping.



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# File 'lib/online_migrations/background_data_migrations/migration.rb', line 118

def stopping?
  STOPPING_STATUSES.include?(status)
end

#stuck? ⇒ Boolean

Returns whether a migration is stuck, which is defined as having a status of cancelling or pausing, and not having been updated in the last 5 minutes.

Returns:

  • (Boolean) —

    whether the migration is stuck.



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# File 'lib/online_migrations/background_data_migrations/migration.rb', line 127

def stuck?
  stuck_timeout = OnlineMigrations.config.background_data_migrations.stuck_timeout
  (cancelling? || pausing?) && updated_at <= stuck_timeout.ago
end