Class: ScoutApm::LayawayFile

Inherits:
Object
  • Object
show all
Defined in:
lib/scout_apm/layaway_file.rb

Instance Method Summary collapse

Instance Method Details

#dump(object) ⇒ Object 



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# File 'lib/scout_apm/layaway_file.rb', line 33

def dump(object)
  Marshal.dump(object)
end

#get_data(f) ⇒ Object 



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# File 'lib/scout_apm/layaway_file.rb', line 74

def get_data(f)
  data = read_until_end(f)
  result = load(data)
  f.truncate(0)
  result
end

#load(dump) ⇒ Object 



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# File 'lib/scout_apm/layaway_file.rb', line 37

def load(dump)
  if dump.size == 0
    ScoutApm::Agent.instance.logger.debug("No data in layaway file.")
    return nil
  end
  Marshal.load(dump)
rescue NameError, ArgumentError, TypeError => e
  ScoutApm::Agent.instance.logger.info("Unable to load data from Layaway file, resetting.")
  ScoutApm::Agent.instance.logger.debug("#{e.message}, #{e.backtrace.join("\n\t")}")
  nil
end

#path ⇒ Object 



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# File 'lib/scout_apm/layaway_file.rb', line 4

def path
  return @path if @path

  candidates = [
    ScoutApm::Agent.instance.config.value("data_file"),
    "#{ScoutApm::Agent.instance.default_log_path}/scout_apm.db",
    "#{ScoutApm::Agent.instance.environment.root}/tmp/scout_apm.db"
  ]

  candidates.each do |candidate|
    next if candidate.nil?

    begin
      ScoutApm::Agent.instance.logger.debug("Checking Layaway File Location: #{candidate}")
      File.open(candidate, "w") { |f| } # Open & Close to check that we can

      # No exception, it is valid
      ScoutApm::Agent.instance.logger.info("Layaway File location found: #{candidate}")
      @path = candidate
      return @path
    rescue Exception
      ScoutApm::Agent.instance.logger.debug("Couldn't open layaway file for test write at #{candidate}")
    end
  end

  ScoutApm::Agent.instance.logger.error("No valid layaway file found, please set a location in the configuration key `data_file`")
  nil
end

#read_and_write ⇒ Object 



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# File 'lib/scout_apm/layaway_file.rb', line 49

def read_and_write
  File.open(path, File::RDWR | File::CREAT) do |f|
    f.flock(File::LOCK_EX)
    begin
      result = (yield get_data(f))
      f.rewind
      f.truncate(0)
      if result
        write(f, dump(result))
      end
    ensure
      f.flock(File::LOCK_UN)
    end
  end
rescue Errno::ENOENT, Exception  => e
  ScoutApm::Agent.instance.logger.error("Unable to access the layaway file [#{e.class} - #{e.message}]. " +
                                        "The user running the app must have read & write access. " +
                                        "Change the path by setting the `data_file` key in scout_apm.yml"
                                       )
  ScoutApm::Agent.instance.logger.debug(e.backtrace.join("\n\t"))

  # ensure the in-memory metric hash is cleared so data doesn't continue to accumulate.
  # ScoutApm::Agent.instance.store.metric_hash = {}
end

#read_until_end(f) ⇒ Object 



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# File 'lib/scout_apm/layaway_file.rb', line 91

def read_until_end(f)
  contents = ""
  while true
    contents << f.read_nonblock(10_000)
  end
rescue Errno::EAGAIN, Errno::EINTR
  IO.select([f])
  retry
rescue EOFError
  contents
end

#write(f, string) ⇒ Object 



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# File 'lib/scout_apm/layaway_file.rb', line 81

def write(f, string)
  result = 0
  while (result < string.length)
    result += f.write_nonblock(string)
  end
rescue Errno::EAGAIN, Errno::EINTR
  IO.select(nil, [f])
  retry
end