Class: PEROBS::DynamoDB

Inherits:
DataBase show all
Defined in:
lib/perobs/DynamoDB.rb

Overview

This class implements an Amazon DynamoDB storage engine for PEROBS.

Constant Summary collapse

INTERNAL_ITEMS = 
%w( config item_counter )

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from DataBase

#check_option, #close, #deserialize, #open, #serialize

Constructor Details

#initialize(db_name, options = {}) ⇒ DynamoDB

Create a new DynamoDB object.

Parameters:

  • db_name (String) —

    name of the DB directory

  • options (Hash) (defaults to: {}) —

    options to customize the behavior. Currently only the following options are supported: :serializer : Can be :json and :yaml :aws_id : AWS credentials ID :aws_key : AWS credentials key :aws_region : AWS region to host the data



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# File 'lib/perobs/DynamoDB.rb', line 51

def initialize(db_name, options = {})
  # :marshal serialization results in a binary format that cannot easily
  # be stored in DynamoDB. We fall back to :yaml.
  if options[:serializer] == :marshal
    options[:serializer] = :yaml
  end

  super(options)

  if options.include?(:aws_id) && options.include?(:aws_key)
    Aws.config[:credentials] = Aws::Credentials.new(options[:aws_id],
                                                    options[:aws_key])
  end
  if options.include?(:aws_region)
    Aws.config[:region] = options[:aws_region]
  end

  @dynamodb = Aws::DynamoDB::Client.new
  @table_name = db_name
  @config = nil
  # The number of items currently stored in the DB.
  @item_counter = nil
  if create_table(@table_name)
    @config = { 'serializer' => @serializer }
    put_hash('config', @config)
    @item_counter = 0
    dynamo_put_item('item_counter', @item_counter.to_s)
  else
    @config = get_hash('config')
    if @config['serializer'] != @serializer
      raise ArgumentError, "DynamoDB #{@table_name} was created with " +
        "serializer #{@config['serializer']} but was now opened with " +
        "serializer #{@serializer}."
    end
    @item_counter = dynamo_get_item('item_counter').to_i
  end

  # Read the existing DB config.
end

Instance Attribute Details

#item_counter ⇒ Object (readonly)

Returns the value of attribute item_counter.



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# File 'lib/perobs/DynamoDB.rb', line 41

def item_counter
  @item_counter
end

Class Method Details

.delete_db(table_name) ⇒ Object 



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# File 'lib/perobs/DynamoDB.rb', line 99

def DynamoDB::delete_db(table_name)
  dynamodb = Aws::DynamoDB::Client.new
  dynamodb.delete_table(:table_name => table_name)
  dynamodb.wait_until(:table_not_exists, table_name: table_name)
end

Instance Method Details

#check(id, repair) ⇒ TrueClass/FalseClass

Check if the stored object is syntactically correct.

Parameters:

  • id (Integer) —

    Object ID

  • repair (TrueClass/FalseClass) —

    True if an repair attempt should be made.

Returns:

  • (TrueClass/FalseClass) —

    True if the object is OK, otherwise false.



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# File 'lib/perobs/DynamoDB.rb', line 210

def check(id, repair)
  begin
    get_object(id)
  rescue => e
    PEROBS.log.error "Cannot read object with ID #{id}: #{e.message}"
    return false
  end

  true
end

#check_db(repair = false) ⇒ Object

Basic consistency check.

Parameters:

  • repair (TrueClass/FalseClass) (defaults to: false) —

    True if found errors should be repaired.



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# File 'lib/perobs/DynamoDB.rb', line 190

def check_db(repair = false)
  unless (item_counter = dynamo_get_item('item_counter')) &&
         item_counter == @item_counter
    PEROBS.log.error "@item_counter variable (#{@item_counter}) and " +
      "item_counter table entry (#{item_counter}) don't match"
  end
  item_counter = 0
  each_item { item_counter += 1 }
  unless item_counter == @item_counter
    PEROBS.log.error "Table contains #{item_counter} items but " +
      "@item_counter is #{@item_counter}"
  end
end

#clear_marks ⇒ Object

This method must be called to initiate the marking process.



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# File 'lib/perobs/DynamoDB.rb', line 152

def clear_marks
  each_item do |id|
    dynamo_mark_item(id, false)
  end
end

#delete_database ⇒ Object

Delete the entire database. The database is no longer usable after this method was called.



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# File 'lib/perobs/DynamoDB.rb', line 93

def delete_database
  dynamodb = Aws::DynamoDB::Client.new
  dynamodb.delete_table(:table_name => @table_name)
  dynamodb.wait_until(:table_not_exists, table_name: @table_name)
end

#delete_unmarked_objects ⇒ Integer

Permanently delete all objects that have not been marked. Those are orphaned and are no longer referenced by any actively used object.

Returns:

  • (Integer) —

    Count of the deleted objects.



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# File 'lib/perobs/DynamoDB.rb', line 161

def delete_unmarked_objects
  deleted_objects_count = 0
  each_item do |id|
    unless dynamo_is_marked?(id)
      dynamo_delete_item(id)
      deleted_objects_count += 1
      @item_counter -= 1
    end
  end
  dynamo_put_item('item_counter', @item_counter.to_s)

  deleted_objects_count
end

#get_hash(name) ⇒ Hash

Load the Hash with the given name.

Parameters:

  • name (String) —

    Name of the hash.

Returns:

  • (Hash) —

    A Hash that maps String objects to strings or numbers.



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# File 'lib/perobs/DynamoDB.rb', line 122

def get_hash(name)
  if (item = dynamo_get_item(name))
    JSON.parse(item)
  else
    ::Hash.new
  end
end

#get_object(id) ⇒ Hash

Load the given object from the filesystem.

Parameters:

  • id (Integer) —

    object ID

Returns:

  • (Hash) —

    Object as defined by PEROBS::ObjectBase or nil if ID does not exist



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# File 'lib/perobs/DynamoDB.rb', line 147

def get_object(id)
  (item = dynamo_get_item(id.to_s)) ? deserialize(item) : nil
end

#include?(id) ⇒ Boolean

Return true if the object with given ID exists

Parameters:

  • id (Integer)

Returns:

  • (Boolean) 


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# File 'lib/perobs/DynamoDB.rb', line 107

def include?(id)
  !dynamo_get_item(id.to_s).nil?
end

#is_marked?(id) ⇒ Boolean

Check if the object is marked.

Parameters:

  • id (Integer) —

    ID of the object to check

Returns:

  • (Boolean) 


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# File 'lib/perobs/DynamoDB.rb', line 183

def is_marked?(id)
  dynamo_is_marked?(id.to_s)
end

#mark(id) ⇒ Object

Mark an object.

Parameters:

  • id (Integer) —

    ID of the object to mark



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# File 'lib/perobs/DynamoDB.rb', line 177

def mark(id)
  dynamo_mark_item(id.to_s, true)
end

#put_hash(name, hash) ⇒ Object

Store a simple Hash as a JSON encoded file into the DB directory. numbers.

Parameters:

  • name (String) —

    Name of the hash. Will be used as file name.

  • hash (Hash) —

    A Hash that maps String objects to strings or



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# File 'lib/perobs/DynamoDB.rb', line 115

def put_hash(name, hash)
  dynamo_put_item(name, hash.to_json)
end

#put_object(obj, id) ⇒ Object

Store the given object into the cluster files.

Parameters:

  • obj (Hash) —

    Object as defined by PEROBS::ObjectBase



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# File 'lib/perobs/DynamoDB.rb', line 132

def put_object(obj, id)
  id_str = id.to_s
  unless dynamo_get_item(id_str)
    # The is no object with this ID yet. Increase the item counter.
    @item_counter += 1
    dynamo_put_item('item_counter', @item_counter.to_s)
  end

  dynamo_put_item(id.to_s, serialize(obj))
end