Class: MongoOplogBackup::Backup

Inherits:
Object
  • Object
show all
Defined in:
lib/mongo_oplog_backup/backup.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(config, backup_name = nil) ⇒ Backup

Returns a new instance of Backup.


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# File 'lib/mongo_oplog_backup/backup.rb', line 21

def initialize(config, backup_name=nil)
  @config = config
  @backup_name = backup_name
  if backup_name.nil?
    state_file = config.global_state_file
    state = JSON.parse(File.read(state_file)) rescue nil
    state ||= {}
    @backup_name = state['backup']
  end
end

Instance Attribute Details

#backup_name ⇒ Object (readonly)

Returns the value of attribute backup_name.


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# File 'lib/mongo_oplog_backup/backup.rb', line 10

def backup_name
  @backup_name
end

#config ⇒ Object (readonly)

Returns the value of attribute config.


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# File 'lib/mongo_oplog_backup/backup.rb', line 10

def config
  @config
end

Instance Method Details

#backup_folder ⇒ Object 


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# File 'lib/mongo_oplog_backup/backup.rb', line 12

def backup_folder
  return nil unless backup_name
  File.join(config.backup_dir, backup_name)
end

#backup_full ⇒ Object 


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# File 'lib/mongo_oplog_backup/backup.rb', line 121

def backup_full
  position = latest_oplog_timestamp
  raise "Cannot backup with empty oplog" if position.nil?
  @backup_name = "backup-#{position}"
  if File.exists? backup_folder
    raise "Backup folder '#{backup_folder}' already exists; not performing backup."
  end
  dump_folder = File.join(backup_folder, 'dump')
  dump_args = ['--out', dump_folder]
  dump_args << '--gzip' if config.use_compression?
  result = config.mongodump(dump_args)
  unless File.directory? dump_folder
    MongoOplogBackup.log.error 'Backup folder does not exist'
    raise 'Full backup failed'
  end

  File.write(File.join(dump_folder, 'debug.log'), result.standard_output)

  unless result.standard_error.length == 0
    File.write(File.join(dump_folder, 'error.log'), result.standard_error)
  end

  write_state({
    'position' => position
  })

  return {
    position: position,
    backup: backup_name
  }
end

#backup_oplog(options = {}) ⇒ Object

Raises:

  • (ArgumentError) 

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# File 'lib/mongo_oplog_backup/backup.rb', line 47

def backup_oplog(options={})
  raise ArgumentError, "No state in #{backup_name}" unless File.exists? state_file

  backup_state = JSON.parse(File.read(state_file))
  start_at = options[:start] || BSON::Timestamp.from_json(backup_state['position'])
  raise ArgumentError, ":start is required" unless start_at

  query = ['--query', "{ts : { $gte : { $timestamp : { t : #{start_at.seconds}, i : #{start_at.increment} } } }}"]

  dump_args = ['--out', config.oplog_dump_folder, '--db', 'local', '--collection', 'oplog.rs']
  dump_args += query
  dump_args << '--gzip' if config.use_compression?
  config.mongodump(dump_args)

  unless File.exists? config.oplog_dump
    raise "mongodump failed"
  end
  MongoOplogBackup.log.debug "Checking timestamps..."
  timestamps = Oplog.oplog_timestamps(config.oplog_dump)

  unless timestamps.increasing?
    raise "Something went wrong - oplog is not ordered."
  end

  first = timestamps[0]
  last = timestamps[-1]

  if first > start_at
    raise "Expected first oplog entry to be #{start_at.inspect} but was #{first.inspect}\n" +
      "The oplog is probably too small.\n" +
      "Increase the oplog size, the start with another full backup."
  elsif first < start_at
    raise "Expected first oplog entry to be #{start_at.inspect} but was #{first.inspect}\n" +
      "Something went wrong in our query."
  end

  result = {
    entries: timestamps.count,
    first: first,
    position: last
  }

  if timestamps.count == 1
    result[:empty] = true
  else
    outfile = "oplog-#{first}-#{last}.bson"
    outfile += '.gz' if config.use_compression?
    full_path = File.join(backup_folder, outfile)
    FileUtils.mkdir_p backup_folder
    FileUtils.mv config.oplog_dump, full_path

    write_state({
      'position' => result[:position]
    })
    result[:file] = full_path
    result[:empty] = false
  end

  FileUtils.rm_r config.oplog_dump_folder rescue nil
  result
end

#latest_oplog_timestamp ⇒ Object 


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# File 'lib/mongo_oplog_backup/backup.rb', line 109

def latest_oplog_timestamp
  script = File.expand_path('../../oplog-last-timestamp.js', File.dirname(__FILE__))
  result_text = config.mongo('admin', script).standard_output
  begin
    response = JSON.parse(result_text)
    return nil unless response['position']
    BSON::Timestamp.from_json(response['position'])
  rescue JSON::ParserError => e
    raise StandardError, "Failed to connect to MongoDB: #{result_text}"
  end
end

#latest_oplog_timestamp_moped ⇒ Object 


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# File 'lib/mongo_oplog_backup/backup.rb', line 190

def latest_oplog_timestamp_moped
  # Alternative implementation for `latest_oplog_timestamp`
  require 'moped'
  session = Moped::Session.new([ "127.0.0.1:27017" ])
  session.use 'local'
  oplog = session['oplog.rs']
  entry = oplog.find.limit(1).sort('$natural' => -1).one
  if entry
    entry['ts']
  else
    nil
  end
end

#lock(lockname, &block) ⇒ Object 


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# File 'lib/mongo_oplog_backup/backup.rb', line 36

def lock(lockname, &block)
  File.open(lockname, File::RDWR|File::CREAT, 0644) do |file|
    # Get a non-blocking lock
    got_lock = file.flock(File::LOCK_EX|File::LOCK_NB)
    if got_lock == false
      raise LockError, "Failed to acquire lock - another backup may be busy"
    end
    yield
  end
end

#perform(mode = :auto, options = {}) ⇒ Object 


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# File 'lib/mongo_oplog_backup/backup.rb', line 153

def perform(mode=:auto, options={})
  FileUtils.mkdir_p config.backup_dir
  have_backup = backup_folder != nil

  if mode == :auto
    if have_backup
      mode = :oplog
    else
      mode = :full
    end
  end

  if mode == :oplog
    raise "Unknown backup position - cannot perform oplog backup. Have you completed a full backup?" unless have_backup
    MongoOplogBackup.log.info "Performing incremental oplog backup"
    lock(File.join(backup_folder, 'backup.lock')) do
      result = backup_oplog
      unless result[:empty]
        new_entries = result[:entries] - 1
        MongoOplogBackup.log.info "Backed up #{new_entries} new entries to #{result[:file]}"
      else
        MongoOplogBackup.log.info "Nothing new to backup"
      end
    end
  elsif mode == :full
    lock(config.global_lock_file) do
      MongoOplogBackup.log.info "Performing full backup"
      result = backup_full
      File.write(config.global_state_file, {
        'backup' => result[:backup]
      }.to_json)
      MongoOplogBackup.log.info "Performed full backup"
    end
    perform(:oplog, options)
  end
end

#state_file ⇒ Object 


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# File 'lib/mongo_oplog_backup/backup.rb', line 17

def state_file
  File.join(backup_folder, 'state.json')
end

#write_state(state) ⇒ Object 


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# File 'lib/mongo_oplog_backup/backup.rb', line 32

def write_state(state)
  File.write(state_file, state.to_json)
end