Class: Vagrant::Util::Subprocess

Inherits:
Object
  • Object
show all
Defined in:
lib/vagrant/util/subprocess.rb

Overview

Execute a command in a subprocess, gathering the results and exit status.

This class also allows you to read the data as it is outputted from the subprocess in real time, by simply passing a block to the execute method.

Defined Under Namespace

Classes: LaunchError, Result, TimeoutExceeded

Constant Summary collapse

READ_CHUNK_SIZE =

The chunk size for reading from subprocess IO.

4096

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(*command) ⇒ Subprocess

Returns a new instance of Subprocess.



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# File 'lib/vagrant/util/subprocess.rb', line 23

def initialize(*command)
  @options = command.last.is_a?(Hash) ? command.pop : {}
  @command = command
  @logger  = Log4r::Logger.new("vagrant::util::subprocess")
end

Class Method Details

.execute(*command, &block) ⇒ Object

Convenience method for executing a method.



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# File 'lib/vagrant/util/subprocess.rb', line 19

def self.execute(*command, &block)
  new(*command).execute(&block)
end

Instance Method Details

#execute ⇒ Object 



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# File 'lib/vagrant/util/subprocess.rb', line 29

def execute
  # Get the timeout, if we have one
  timeout = @options[:timeout]

  # Get the working directory
  workdir = @options[:workdir] || Dir.pwd

  # Get what we're interested in being notified about
  notify  = @options[:notify] || []
  notify  = [notify] if !notify.is_a?(Array)
  if notify.empty? && block_given?
    # If a block is given, subscribers must be given, otherwise the
    # block is never called. This is usually NOT what you want, so this
    # is an error.
    message = "A list of notify subscriptions must be given if a block is given"
    raise ArgumentError, message
  end

  # Let's get some more useful booleans that we access a lot so
  # we're not constantly calling an `include` check
  notify_table = {}
  notify_table[:stderr] = notify.include?(:stderr)
  notify_table[:stdout] = notify.include?(:stdout)
  notify_stdin  = notify.include?(:stdin)

  # Build the ChildProcess
  @logger.info("Starting process: #{@command.inspect}")
  process = ChildProcess.build(*@command)

  # Create the pipes so we can read the output in real time as
  # we execute the command.
  stdout, stdout_writer = IO.pipe
  stderr, stderr_writer = IO.pipe
  process.io.stdout = stdout_writer
  process.io.stderr = stderr_writer
  process.duplex = true

  # Set the environment on the process if we must
  if @options[:env]
    @options[:env].each do |k, v|
      process.environment[k] = v
    end
  end

  # Start the process
  begin
    Dir.chdir(workdir) do
      process.start
    end
  rescue ChildProcess::LaunchError => ex
    # Raise our own version of the error so that users of the class
    # don't need to be aware of ChildProcess
    raise LaunchError.new(ex.message)
  end

  # Make sure the stdin does not buffer
  process.io.stdin.sync = true

  if RUBY_PLATFORM != "java"
    # On Java, we have to close after. See down the method...
    # Otherwise, we close the writers right here, since we're
    # not on the writing side.
    stdout_writer.close
    stderr_writer.close
  end

  # Create a dictionary to store all the output we see.
  io_data = { :stdout => "", :stderr => "" }

  # Record the start time for timeout purposes
  start_time = Time.now.to_i

  @logger.debug("Selecting on IO")
  while true
    writers = notify_stdin ? [process.io.stdin] : []
    results = IO.select([stdout, stderr], writers, nil, timeout || 0.1)
    results ||= []
    readers = results[0]
    writers = results[1]

    # Check if we have exceeded our timeout
    raise TimeoutExceeded, process.pid if timeout && (Time.now.to_i - start_time) > timeout

    # Check the readers to see if they're ready
    if readers && !readers.empty?
      readers.each do |r|
        # Read from the IO object
        data = read_io(r)

        # We don't need to do anything if the data is empty
        next if data.empty?

        io_name = r == stdout ? :stdout : :stderr
        @logger.debug("#{io_name}: #{data.chomp}")

        io_data[io_name] += data
        yield io_name, data if block_given? && notify_table[io_name]
      end
    end

    # Break out if the process exited. We have to do this before
    # attempting to write to stdin otherwise we'll get a broken pipe
    # error.
    break if process.exited?

    # Check the writers to see if they're ready, and notify any listeners
    if writers && !writers.empty?
      yield :stdin, process.io.stdin if block_given?
    end
  end

  # Wait for the process to end.
  begin
    remaining = (timeout || 32000) - (Time.now.to_i - start_time)
    remaining = 0 if remaining < 0
    @logger.debug("Waiting for process to exit. Remaining to timeout: #{remaining}")

    process.poll_for_exit(remaining)
  rescue ChildProcess::TimeoutError
    raise TimeoutExceeded, process.pid
  end

  @logger.debug("Exit status: #{process.exit_code}")

  # Read the final output data, since it is possible we missed a small
  # amount of text between the time we last read data and when the
  # process exited.
  [stdout, stderr].each do |io|
    # Read the extra data, ignoring if there isn't any
    extra_data = read_io(io)
    next if extra_data == ""

    # Log it out and accumulate
    io_name = io == stdout ? :stdout : :stderr
    io_data[io_name] += extra_data
    @logger.debug("#{io_name}: #{extra_data.chomp}")

    # Yield to any listeners any remaining data
    yield io_name, extra_data if block_given?
  end

  if RUBY_PLATFORM == "java"
    # On JRuby, we need to close the writers after the process,
    # for some reason. See GH-711.
    stdout_writer.close
    stderr_writer.close
  end

  # Return an exit status container
  return Result.new(process.exit_code, io_data[:stdout], io_data[:stderr])
end