class ActiveRecord::Middleware::DatabaseSelector::Resolver

:nodoc:
if it’s been 2 seconds since the last write.
By default the Resolver class will send read traffic to the replica
be changed.
DatabaseSelector::Resolver and implements the methods that need to
create a custom resolver class that inherits from
To change the behavior of the Resolver class in your application,
determine which database the request should use.
The Resolver class is used by the DatabaseSelector middleware to

def self.call(context, options = {}) 

def self.call(context, options = {})
  new(context, options)
end

def initialize(context, options = {}) 

def initialize(context, options = {})
  @context = context
  @options = options
  @delay = @options && @options[:delay] ? @options[:delay] : SEND_TO_REPLICA_DELAY
  @instrumenter = ActiveSupport::Notifications.instrumenter
end

def read(&blk) 

def read(&blk)
  if read_from_primary?
    read_from_primary(&blk)
  else
    read_from_replica(&blk)
  end
end

def read_from_primary(&blk) 

def read_from_primary(&blk)
  ActiveRecord::Base.connected_to(role: ActiveRecord.writing_role, prevent_writes: true) do
    instrumenter.instrument("database_selector.active_record.read_from_primary", &blk)
  end
end

def read_from_primary? 

def read_from_primary?
  !time_since_last_write_ok?
end

def read_from_replica(&blk) 

def read_from_replica(&blk)
  ActiveRecord::Base.connected_to(role: ActiveRecord.reading_role, prevent_writes: true) do
    instrumenter.instrument("database_selector.active_record.read_from_replica", &blk)
  end
end

def send_to_replica_delay 

def send_to_replica_delay
  delay
end

def time_since_last_write_ok? 

def time_since_last_write_ok?
  Time.now - context.last_write_timestamp >= send_to_replica_delay
end

def update_context(response) 

def update_context(response)
  context.save(response)
end

def write(&blk) 

def write(&blk)
  write_to_primary(&blk)
end

def write_to_primary 

def write_to_primary
  ActiveRecord::Base.connected_to(role: ActiveRecord.writing_role, prevent_writes: false) do
    instrumenter.instrument("database_selector.active_record.wrote_to_primary") do
      yield
    ensure
      context.update_last_write_timestamp
    end
  end
end