Module: Cabin::Mixins::Pipe

Included in:
Channel
Defined in:
lib/cabin/mixins/pipe.rb

Overview

This module provides a ‘pipe’ method which instructs cabin to pipe anything read from the IO given to be logged.

Instance Method Summary collapse

Instance Method Details

#pipe(io_to_method_map, &block) ⇒ Object

Pipe IO objects to method calls on a logger.

The argument is a hash of IO to method symbols. 

logger.pipe(io => :the_method)

For each line read from ‘io’, logger.the_method(the_line) will be called.

Example:

cmd = "strace -e trace=write date"
Open4::popen4(cmd) do |pid, stdin, stdout, stderr|
  stdin.close

  # Make lines from stdout be logged as 'info'
  # Make lines from stderr be logged as 'error'
  logger.pipe(stdout => :info, stderr => :error)
end

Output:

write(1, "Fri Jan 11 22:49:42 PST 2013\n", 29) = 29 {"level":"error"}
Fri Jan 11 22:49:42 PST 2013 {"level":"info"}
+++ exited with 0 +++ {"level":"error"}



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# File 'lib/cabin/mixins/pipe.rb', line 31

def pipe(io_to_method_map, &block)
  fds = io_to_method_map.keys

  while !fds.empty?
    readers, _, _ = IO.select(fds, nil, nil, nil)
    readers.each do |fd|
      begin
        line = fd.readline.chomp
      rescue EOFError
        fd.close rescue nil
        fds.delete(fd)
        next
      end

      method_name = io_to_method_map[fd]
      block.call(line, method_name) if block_given?
      send(method_name, line)
    end # readers.each
  end # while !fds.empty?
end