class Evanescent

IO like object, that can be used with any logging class (such as Ruby’s native Logger). This object will save its input to a file, and allows:

Hourly or daily rotation.
Compression of rotated files.
Removal of old compressed files.

This functionality supplement logging classes, allowing everything related to logging management, to be done within Ruby, without relying on external tools (such as logrotate).

Constants

PARAMS

Attributes

keep[R]

How long rotated files are kept (in seconds).

path[R]

Current path being written to.

rotation[R]

Rotation policy.

Public Class Methods

logger(opts) click to toggle source

Shortcut for: Logger.new(Evanescent.new(opts)). Requires logger if needed.

# File lib/evanescent.rb, line 24
def self.logger opts
  unless Object.const_defined? :Logger
    require 'logger'
  end
  Logger.new(
    self.new(opts)
  )
end

new(opts) click to toggle source

Must receive a Hash with:

:path: Path where to write to.
:rotation: Either :hourly or :daily.
:keep: For how long to keep rotated files. It is parsed with chronic_duration Gem natural language features. Examples: ‘1 day’, ‘1 month’.

# File lib/evanescent.rb, line 37
def initialize opts
  @path = opts[:path]
  @rotation = opts[:rotation]
  @keep = ChronicDuration.parse(opts[:keep])
  @mutex = Mutex.new
  @last_prefix = make_suffix(Time.now)
  @io = nil
  @compress_thread = nil
end

Public Instance Methods

close() click to toggle source

Close file.

# File lib/evanescent.rb, line 70
def close
  @mutex.synchronize do
    @io.close
  end
end

wait_compression() click to toggle source

Compression is done in a separate thread. This method suspends current thread execution until existing compression thread returns. If no compression thread is running, returns immediately.

# File lib/evanescent.rb, line 77
def wait_compression
  if @compress_thread
    begin
      @compress_thread.join
    rescue
      warn("Compression thread failed: #{$!} (#{$!.class})")
    ensure
      @compress_thread = nil
    end
  end
end

write(string) click to toggle source

Writes to path and rotate, compress and purge if necessary.

# File lib/evanescent.rb, line 48
def write string
  @mutex.synchronize do
    if new_path = rotation_path
      # All methods here must have exceptions threated. See:
      # https://github.com/ruby/ruby/blob/3e92b635fb5422207b7bbdc924e292e51e21f040/lib/logger.rb#L647
      purge
      mv_path(new_path)
      compress
    end
    open_io
    if @io
      # No exceptions threated here, they should be handled by caller. See:
      # https://github.com/ruby/ruby/blob/3e92b635fb5422207b7bbdc924e292e51e21f040/lib/logger.rb#L653
      @io.write(string)
    else
      warn("Unable to log: '#{path}' not open!")
      0
    end
  end
end

Private Instance Methods

compress() click to toggle source

# File lib/evanescent.rb, line 163
def compress
  wait_compression
  @compress_thread = Thread.new do
    Dir.glob("#{path}.#{PARAMS[rotation][:glob]}").each do |uncompressed|
      compressed = "#{uncompressed}.gz"
      Zlib::GzipWriter.open(compressed) do |gz|
        gz.mtime = File.mtime(uncompressed)
        gz.orig_name = uncompressed
        File.open(uncompressed, 'r') do |io|
          io.binmode
          io.each do |data|
            gz.write(data)
          end
        end
      end
      File.delete(uncompressed)
    end
  end
rescue
  warn("Error compressing files: #{$!} (#{$!.class})")
end

make_suffix(time) click to toggle source

# File lib/evanescent.rb, line 104
def make_suffix time
  time.strftime(PARAMS[rotation][:strftime])
end

mv_path(new_path) click to toggle source

# File lib/evanescent.rb, line 157
def mv_path new_path
  FileUtils.mv(path, new_path)
rescue
  warn("Error renaming '#{path}' to '#{new_path}': #{$!} (#{$!.class})")
end

open_io() click to toggle source

# File lib/evanescent.rb, line 108
def open_io
  unless @io
    @io = File.open(path, File::APPEND | File::CREAT | File::WRONLY)
    @io.sync = true
  end
rescue
  warn("Unable to open '#{path}': #{$!} (#{$!.class})")
end

purge() click to toggle source

# File lib/evanescent.rb, line 141
def purge
  Dir.glob("#{path}.#{PARAMS[rotation][:glob]}.gz").each do |compressed|
    time_extractor = Regexp.new(
      '^' + Regexp.escape("#{path}.") + "(?<time>.+)" + Regexp.escape(".gz") + '$'
    )
    time_string = compressed.match(time_extractor)[:time]
    compressed_time = Time.strptime(time_string, PARAMS[rotation][:strftime])
    age = Time.now - compressed_time
    if age >= keep
      File.delete(compressed)
    end
  end
rescue
  warn("Error purging old files: #{$!} (#{$!.class})")
end

rotation_path() click to toggle source

Returns new path for rotation. If no rotation is needed, returns nil.

# File lib/evanescent.rb, line 118
def rotation_path
  if @io
    curr_suffix = make_suffix(Time.now)
    return nil if curr_suffix == @last_prefix
    # Same as https://github.com/ruby/ruby/blob/3e92b635fb5422207b7bbdc924e292e51e21f040/lib/logger.rb#L760
    begin
      @io.close
    rescue
      warn("Error closing '#{path}': #{$!} (#{$!.class})")
    end
    @io = nil
    @last_prefix = curr_suffix
    "#{path}.#{curr_suffix}"
  else
    return nil unless File.exist?(path)
    curr_suffix = make_suffix(Time.now+PARAMS[rotation][:interval])
    rotation_suffix = make_suffix(File.mtime(path) + PARAMS[rotation][:interval])
    return nil if curr_suffix == rotation_suffix
    @last_prefix = curr_suffix
    "#{path}.#{rotation_suffix}"
  end
end