fluentd-ui/app/models/fluentd_log.rb

class FluentdLog
  attr_reader :log_file

  def initialize(path)
    @log_file = path
  end

  def read
    return "" unless File.exists?(log_file)
    content = File.open(log_file, "r+:ascii-8bit"){|f| f.read } # TODO: large log file
    content.force_encoding('utf-8').valid_encoding? ? content : content.force_encoding('ascii-8bit')
  end

  def errors_since(since = 1.day.ago)
    errors = []
    logged_errors do |error|
      break if Time.parse(error[:subject]) < since
      errors << error
    end
    errors
  end

  def recent_errors(limit = 3)
    errors = []
    logged_errors do |error|
      errors << error
      break if errors.length >= limit
    end
    errors
  end

  def last_error_message
    recent_errors(1).first.try(:[], :subject) || ""
  end

  def tail(limit = nil)
    return [] unless File.exists?(log_file)

    limit = limit.to_i rescue 0
    limit = limit.zero? ? Settings.default_log_tail_count : limit
    io = File.open(log_file)
    buf = []
    reader = ::FileReverseReader.new(io)
    reader.each_line do |line|
      buf << line
      break if buf.length >= limit
    end
    buf
  end

  private

  def logged_errors(&block)
    return [] unless File.exist?(log_file)
    buf = []
    io = File.open(log_file)
    reader = ::FileReverseReader.new(io)
    reader.each_line do |line|
      unless line["error"]
        if buf.present?
          # NOTE: if a following log is given
          #         2014-06-30 11:24:08 +0900 [error]: unexpected error error_class=Errno::EADDRINUSE error=#<Errno::EADDRINUSE: Address already in use - bind(2) for 0.0.0.0:24220>
          #         2014-06-30 11:24:08 +0900 [error]: /Users/uu59/.rbenv/versions/2.1.2/lib/ruby/2.1.0/socket.rb:206:in `bind'
          #         2014-06-30 11:24:08 +0900 [error]: /Users/uu59/.rbenv/versions/2.1.2/lib/ruby/2.1.0/socket.rb:206:in `listen'
          #         2014-06-30 11:24:08 +0900 [error]: /Users/uu59/.rbenv/versions/2.1.2/lib/ruby/2.1.0/socket.rb:461:in `block in tcp_server_sockets'
          #       the first line become a "subject", trailing lines are "notes"
          #       {
          #         subject: "2014-06-30 11:24:08 +0900 [error]: unexpected error error_class=Errno::EADDRINUSE error=#<Errno::EADDRINUSE: Address already in use - bind(2) for 0.0.0.0:24220>",
          #         notes: [
          #           2014-06-30 11:24:08 +0900 [error]: /Users/uu59/.rbenv/versions/2.1.2/lib/ruby/2.1.0/socket.rb:206:in `bind'
          #           2014-06-30 11:24:08 +0900 [error]: /Users/uu59/.rbenv/versions/2.1.2/lib/ruby/2.1.0/socket.rb:206:in `listen'
          #           2014-06-30 11:24:08 +0900 [error]: /Users/uu59/.rbenv/versions/2.1.2/lib/ruby/2.1.0/socket.rb:461:in `block in tcp_server_sockets'
          #         ]
          #       }
          split_error_lines_to_error_units(buf.reverse).each do |error_unit|
            block.call({
              subject: error_unit[:subject],
              notes: error_unit[:notes],
            })
          end
        end

        buf = []
        next
      end
      buf << line
    end
  ensure
    io && io.close
  end

  def split_error_lines_to_error_units(buf)
    # NOTE: if a following log is given
    #
    #2014-05-27 10:54:37 +0900 [error]: unexpected error error_class=Errno::EADDRINUSE error=#<Errno::#EADDRINUSE: Address already in use - bind(2) for "0.0.0.0" port 24224>
    #2014-05-27 10:55:40 +0900 [error]: unexpected error error_class=Errno::EADDRINUSE error=#<Errno::#EADDRINUSE: Address already in use - bind(2) for "0.0.0.0" port 24224>
    #  2014-05-27 10:55:40 +0900 [error]: /Users/uu59/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/cool.io-1.2.4/lib/cool.io/server.rb:57:in `initialize'
    #  2014-05-27 10:55:40 +0900 [error]: /Users/uu59/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/cool.io-1.2.4/lib/cool.io/server.rb:57:in `new'
    #
    #the first line and second line must be each "error_unit". and after third lines lines are "notes" of second error unit of .
    # [
    #   { subject: "2014-05-27 10:54:37 +0900 [error]: unexpected error error_class=Errno::EADDRINUSE error=#<Errno::#EADDRINUSE: Address already in use - bind(2) for "0.0.0.0" port 24224>          ",
    #     notes: [] },
    #   { subject: "2014-05-27 10:55:40 +0900 [error]: unexpected error error_class=Errno::EADDRINUSE error=#<Errno::#EADDRINUSE: Address already in use - bind(2) for "0.0.0.0" port 24224>          ",
    #     notes: [
    #       "2014-05-27 10:55:40 +0900 [error]: /Users/uu59/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/cool.io-1.2.4/lib/cool.io/server.rb:57:in `initialize'",
    #       "2014-05-27 10:55:40 +0900 [error]: /Users/uu59/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/cool.io-1.2.4/lib/cool.io/server.rb:57:in `new'"
    #     ]
    #   },
    # ]
    #
    return_array = []
    buf.each_with_index do |b, i|
      if b.match(/\A /)
        return_array[-1][:notes] << b
      else
        return_array << { subject: b, notes: [] }
      end
    end
    return return_array.reverse
  end
end