Class: Gizzard::Migrator

Inherits:
Object
  • Object
show all
Defined in:
lib/gizzard/migrator.rb

Constant Summary collapse

BALANCE_TOLERANCE = 
1

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(existing_map, config_templates, default_total_shards, config) ⇒ Migrator

Returns a new instance of Migrator.



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# File 'lib/gizzard/migrator.rb', line 23

def initialize(existing_map, config_templates, default_total_shards, config)
  @configured_templates = config_templates
  @existing_map = existing_map

  @existing_templates = existing_map.keys
  @total_shards = @existing_map.values.map { |a| a.length }.inject { |a, b| a + b } || default_total_shards
  @config = config

  derive_changes
end

Instance Attribute Details

#configured_templates ⇒ Object (readonly)

Returns the value of attribute configured_templates.



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# File 'lib/gizzard/migrator.rb', line 18

def configured_templates
  @configured_templates
end

#existing_map ⇒ Object (readonly)

Returns the value of attribute existing_map.



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# File 'lib/gizzard/migrator.rb', line 18

def existing_map
  @existing_map
end

#existing_templates ⇒ Object (readonly)

Returns the value of attribute existing_templates.



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# File 'lib/gizzard/migrator.rb', line 18

def existing_templates
  @existing_templates
end

#new_templates ⇒ Object (readonly)

populated via derive_changes



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# File 'lib/gizzard/migrator.rb', line 21

def new_templates
  @new_templates
end

#similar_templates ⇒ Object (readonly)

populated via derive_changes



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# File 'lib/gizzard/migrator.rb', line 21

def similar_templates
  @similar_templates
end

#total_shards ⇒ Object (readonly)

Returns the value of attribute total_shards.



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# File 'lib/gizzard/migrator.rb', line 18

def total_shards
  @total_shards
end

#unchanged_templates ⇒ Object (readonly)

populated via derive_changes



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# File 'lib/gizzard/migrator.rb', line 21

def unchanged_templates
  @unchanged_templates
end

#unrecognized_templates ⇒ Object (readonly)

populated via derive_changes



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# File 'lib/gizzard/migrator.rb', line 21

def unrecognized_templates
  @unrecognized_templates
end

Instance Method Details

#cleanup!(nameserver) ⇒ Object 



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# File 'lib/gizzard/migrator.rb', line 46

def cleanup!(nameserver)
  transformations.each {|t| t.cleanup! nameserver, @config }
end

#copy!(nameserver) ⇒ Object 



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# File 'lib/gizzard/migrator.rb', line 38

def copy!(nameserver)
  transformations.each {|t| t.copy! nameserver, @config }
end

#prepare!(nameserver) ⇒ Object 



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# File 'lib/gizzard/migrator.rb', line 34

def prepare!(nameserver)
  transformations.each {|t| t.prepare! nameserver, @config }
end

#transformations ⇒ Object 



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# File 'lib/gizzard/migrator.rb', line 50

def transformations
  return @transformations if @transformations

  # no changes
  return @transformations = [] if similar_templates.empty? and unrecognized_templates.empty? and new_templates.empty?

  configured_map = configured_templates.inject({}) {|h, t| h.update t => [] }

  @transformations = []

  if existing_templates.empty?
    # no forwardings exist, we must populate the forwarding index.
    forwardings = generate_new_forwardings(total_shards)

    # add the new shard ids to a member of the configured map. will
    # be rebalanced later.
    configured_map.values.first.concat forwardings.values

    @transformations << ForwardingTransformation.new(@config.table_id, forwardings.inject({}) {|f, (b, e)| f.update b => @config.shard_name(e) })
  end

  # map the unchanged templates straight over
  move_unchanged(existing_map, configured_map)

  # map similar templates over to their new versions
  move_similar(existing_map, configured_map)

  # move shards from unrecognized templates to new templates (or
  # existing ones)
  move_unrecognized_to_new(existing_map, configured_map)

  # rebalance
  rebalance_shards(configured_map)

  # transformation generation
  @transformations = generate_transformations(existing_map, configured_map) + @transformations
end

#wait_for_copies(nameserver) ⇒ Object 



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# File 'lib/gizzard/migrator.rb', line 42

def wait_for_copies(nameserver)
  transformations.each {|t| t.wait_for_copies nameserver, @config }
end