Class: MysqlBinlog::BinlogFileReader

Inherits:
Object
  • Object
show all
Defined in:
lib/mysql_binlog/reader/binlog_file_reader.rb

Overview

Read a binary log from a file on disk.

Constant Summary collapse

MAGIC_SIZE = 
4
MAGIC_VALUE = 
1852400382

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(filename) ⇒ BinlogFileReader

Returns a new instance of BinlogFileReader.



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# File 'lib/mysql_binlog/reader/binlog_file_reader.rb', line 9

def initialize(filename)
  @tail = false
  open_file(filename)
end

Instance Attribute Details

#tail ⇒ Object

Returns the value of attribute tail.



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# File 'lib/mysql_binlog/reader/binlog_file_reader.rb', line 7

def tail
  @tail
end

Instance Method Details

#end? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/mysql_binlog/reader/binlog_file_reader.rb', line 66

def end?
  return false if tail
  @binlog.eof?
end

#filename ⇒ Object 



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# File 'lib/mysql_binlog/reader/binlog_file_reader.rb', line 46

def filename
  @filename
end

#open_file(filename) ⇒ Object 



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# File 'lib/mysql_binlog/reader/binlog_file_reader.rb', line 20

def open_file(filename)
  @dirname  = File.dirname(filename)
  @filename = File.basename(filename)
  @binlog   = File.open(filename, mode="r")

  verify_magic
end

#position ⇒ Object 



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# File 'lib/mysql_binlog/reader/binlog_file_reader.rb', line 50

def position
  @binlog.tell
end

#read(length) ⇒ Object 



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# File 'lib/mysql_binlog/reader/binlog_file_reader.rb', line 79

def read(length)
  if tail
    needed_position = position + length
    while @binlog.stat.size < needed_position
      sleep 0.02
    end
  end
  return "" if length == 0
  data = @binlog.read(length)
  if !data
    raise MalformedBinlogException.new
  elsif data.length == 0
    raise ZeroReadException.new
  elsif data.length < length
    raise ShortReadException.new
  end
  data
end

#remaining(header) ⇒ Object 



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# File 'lib/mysql_binlog/reader/binlog_file_reader.rb', line 71

def remaining(header)
  header[:next_position] - @binlog.tell
end

#rewind ⇒ Object 



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# File 'lib/mysql_binlog/reader/binlog_file_reader.rb', line 54

def rewind
  seek(MAGIC_SIZE)
end

#rotate(filename, position) ⇒ Object 



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# File 'lib/mysql_binlog/reader/binlog_file_reader.rb', line 28

def rotate(filename, position)
  retries = 10
  begin
    open_file(@dirname + "/" + filename)
    seek(position)
  rescue Errno::ENOENT
    # A rotate event will be seen in the previous log file before the
    # new file exists. Retry a few times with a little sleep to give
    # the server a chance to create the new file.
    if (retries -= 1) > 0
      sleep 0.01
      retry
    else
      raise
    end
  end
end

#seek(pos) ⇒ Object 



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# File 'lib/mysql_binlog/reader/binlog_file_reader.rb', line 58

def seek(pos)
  @binlog.seek(pos)
end

#skip(header) ⇒ Object 



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# File 'lib/mysql_binlog/reader/binlog_file_reader.rb', line 75

def skip(header)
  seek(header[:next_position])
end

#unget(char) ⇒ Object 



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# File 'lib/mysql_binlog/reader/binlog_file_reader.rb', line 62

def unget(char)
  @binlog.ungetc(char)
end

#verify_magic ⇒ Object 



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# File 'lib/mysql_binlog/reader/binlog_file_reader.rb', line 14

def verify_magic
  if (magic = read(MAGIC_SIZE).unpack("V").first) != MAGIC_VALUE
    raise MalformedBinlogException.new("Magic number #{magic} is incorrect")
  end
end