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

Returns a new instance of Backup.



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

def initialize(config)
  @config = config
end

Instance Attribute Details

#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_full ⇒ Object 



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# File 'lib/mongo_oplog_backup/backup.rb', line 95

def backup_full
  position = latest_oplog_timestamp
  raise "Cannot backup with empty oplog" if position.nil?
  backup_name = "backup-#{position}"
  dump_folder = File.join(config.backup_dir, backup_name, 'dump')
  config.mongodump("--out #{dump_folder}")
  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 26

def backup_oplog(options={})
  start_at = options[:start]
  backup = options[:backup]
  raise ArgumentError, ":backup is required" unless backup
  raise ArgumentError, ":start is required" unless start_at

  if start_at
    query = "--query \"{ts : { \\$gte : { \\$timestamp : { t : #{start_at.seconds}, i : #{start_at.increment} } } }}\""
  else
    query = ""
  end
  config.mongodump("--out #{config.oplog_dump_folder} --db local --collection oplog.rs #{query}")

  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"
    full_path = File.join(config.backup_dir, backup, outfile)
    FileUtils.mkdir_p File.join(config.backup_dir, backup)
    FileUtils.mv config.oplog_dump, full_path

    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 83

def latest_oplog_timestamp
  script = File.expand_path('../../oplog-last-timestamp.js', File.dirname(__FILE__))
  result_text = config.mongo('admin', script)
  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 166

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 16

def lock(lockname, &block)
  File.open(lockname, File::RDWR|File::CREAT, 0644) do |file|
    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 107

def perform(mode=:auto, options={})
  if_not_busy = options[:if_not_busy] || false

  perform_oplog_afterwards = false

  FileUtils.mkdir_p config.backup_dir
  lock(config.lock_file) do
    state_file = config.state_file
    state = JSON.parse(File.read(state_file)) rescue nil
    state ||= {}
    have_position = (state['position'] && state['backup'])

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

    if mode == :oplog
      raise "Unknown backup position - cannot perform oplog backup." unless have_position
      MongoOplogBackup.log.info "Performing incremental oplog backup"
      position = BSON::Timestamp.from_json(state['position'])
      result = backup_oplog(start: position, backup: state['backup'])
      unless result[:empty]
        new_entries = result[:entries] - 1
        state['position'] = result[:position]
        File.write(state_file, state.to_json)
        MongoOplogBackup.log.info "Backed up #{new_entries} new entries to #{result[:file]}"
      else
        MongoOplogBackup.log.info "Nothing new to backup"
      end
    elsif mode == :full
      MongoOplogBackup.log.info "Performing full backup"
      result = backup_full
      state = result
      File.write(state_file, state.to_json)
      MongoOplogBackup.log.info "Performed full backup"

      perform_oplog_afterwards = true
    end
  end

  # Has to be outside the lock
  if perform_oplog_afterwards
    # Oplog backup
    perform(:oplog, options)
  end

rescue LockError => e
  if if_not_busy
    MongoOplogBackup.log.info e.message
    MongoOplogBackup.log.info 'Not performing backup'
  else
    raise
  end
end