Class: Rundoc::CodeCommand::Background::ProcessSpawn

Inherits:
Object
  • Object
show all
Defined in:
lib/rundoc/code_command/background/process_spawn.rb

Overview

This class is responsible for running processes in the background

By default it logs output to a file. This can be used to “wait” for a specific output before continuing:

server = ProcessSpawn("rails server")
server.wait("Use Ctrl-C to stop")

The process can be queried for it’s status to check if it is still booted or not. the process can also be manually stopped:

server = ProcessSpawn("rails server")
server.alive? # => true
server.stop
server.alive? # => false

There are class level methods that can be used to “name” and record background processes. They can be used like this:

server = ProcessSpawn("rails server")
ProcessSpawn.add("muh_server", server)
ProcessSpawn.find("muh_server") # => <# ProcessSpawn instance >
ProcessSpawn.find("foo") # => RuntimeError "Could not find task with name 'foo', ..."

Class Attribute Summary collapse

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(command, timeout: 5, log: Tempfile.new("log"), out: "2>&1") ⇒ ProcessSpawn

Returns a new instance of ProcessSpawn.



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# File 'lib/rundoc/code_command/background/process_spawn.rb', line 47

def initialize(command, timeout: 5, log: Tempfile.new("log"), out: "2>&1")
  @command = command
  @timeout_value = timeout
  @log_reference = log # https://twitter.com/schneems/status/1285289971083907075

  @log = Pathname.new(log)
  @log.dirname.mkpath
  FileUtils.touch(@log)
  @pipe_output, @pipe_input = IO.pipe

  @command = "/usr/bin/env bash -c #{@command.shellescape} >> #{@log} #{out}"
  @pid = nil
end

Class Attribute Details

.tasks ⇒ Object (readonly)

Returns the value of attribute tasks.



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# File 'lib/rundoc/code_command/background/process_spawn.rb', line 31

def tasks
  @tasks
end

Instance Attribute Details

#command ⇒ Object (readonly)

Returns the value of attribute command.



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# File 'lib/rundoc/code_command/background/process_spawn.rb', line 45

def command
  @command
end

#log ⇒ Object (readonly)

Returns the value of attribute log.



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# File 'lib/rundoc/code_command/background/process_spawn.rb', line 45

def log
  @log
end

#pid ⇒ Object (readonly)

Returns the value of attribute pid.



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# File 'lib/rundoc/code_command/background/process_spawn.rb', line 45

def pid
  @pid
end

Class Method Details

.add(name, value) ⇒ Object 



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# File 'lib/rundoc/code_command/background/process_spawn.rb', line 35

def self.add(name, value)
  raise "Task named #{name.inspect} is already started, choose a different name" if @tasks[name]
  @tasks[name] = value
end

.find(name) ⇒ Object 



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# File 'lib/rundoc/code_command/background/process_spawn.rb', line 40

def self.find(name)
  raise "Could not find task with name #{name.inspect}, known task names: #{@tasks.keys.inspect}" unless @tasks[name]
  @tasks[name]
end

Instance Method Details

#alive? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/rundoc/code_command/background/process_spawn.rb', line 87

def alive?
  return false unless @pid
  Process.kill(0, @pid)
rescue Errno::ESRCH, Errno::EPERM
  false
end

#check_alive! ⇒ Object 



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# File 'lib/rundoc/code_command/background/process_spawn.rb', line 132

def check_alive!
  raise "#{@original_command} has exited unexpectedly: #{@log.read}" unless alive?
end

#stdin_write(contents, ending: $/, timeout: timeout_value, wait: nil) ⇒ Object

Writes the contents along with an optional ending character to the STDIN of the backtround process

Parameters:

  • contents (String) —

    the contents to write to the STDIN of the background process

  • ending (String) (defaults to: $/) —

    an optional string to append to the contents before writing default is a newline if you don’t want an ending, pass ‘“”`

  • timeout (Integer) (defaults to: timeout_value) —

    the number of seconds to wait before raising a Timeout::Error when writing to STDIN or waiting for a string to appear in the logs. That means that the process can wait for a maximum of ‘timeout * 2` seconds before raising a Timeout::Error.

  • wait (String) (defaults to: nil) —

    the string to wait for in the logs before continuing. There’s a race condition if the process is in the middle of printing out something to the logs, then the output you’re waiting form might not come as a result of the stdin_write.



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# File 'lib/rundoc/code_command/background/process_spawn.rb', line 105

def stdin_write(contents, ending: $/, timeout: timeout_value, wait: nil)
  log_file = File.new(@log)
  before_write_bytes = log_file.size
  begin
    Timeout.timeout(Integer(timeout)) do
      @pipe_input.print(contents + ending)
      @pipe_input.flush
    end
  rescue Timeout::Error
    raise "Timeout (#{timeout}s) waiting to write #{contents} to stdin. Log contents:\n'#{log.read}'"
  end

  # Ignore bytes written before we sent the STDIN message
  log_file.seek(before_write_bytes)
  wait(wait, timeout, file: log_file)
  contents
end

#stop ⇒ Object 



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# File 'lib/rundoc/code_command/background/process_spawn.rb', line 123

def stop
  return unless alive?
  @pipe_input.close
  Process.kill("TERM", -Process.getpgid(@pid))
  Process.wait(@pid)
rescue Errno::ESRCH => e
  puts "Error stopping process (command: #{command}): #{e}"
end

#wait(wait_value = nil, timeout_value = @timeout_value, file: @log) ⇒ Object

Wait until a given string is found in the logs

If the string is not found within the timeout, a Timeout::Error is raised

Caution: The logs will not be cleared before waiting, so if the string is already present from a prior operation, then it will not wait at all.

To ensure you’re waiting for a brand new string, call ‘log.truncate(0)` first. which is accessible via `:::– background.log.clear` in rundoc syntax.

Parameters:

  • wait_value (String) (defaults to: nil) —

    the string to wait for

  • timeout_value (Integer) (defaults to: @timeout_value) —

    the number of seconds to wait before raising a Timeout::Error

  • file (Pathname) (defaults to: @log) —

    the file to read from, default is the log file



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# File 'lib/rundoc/code_command/background/process_spawn.rb', line 74

def wait(wait_value = nil, timeout_value = @timeout_value, file: @log)
  call
  return unless wait_value

  Timeout.timeout(Integer(timeout_value)) do
    until file.read.include?(wait_value)
      sleep 0.01
    end
  end
rescue Timeout::Error
  raise "Timeout (#{timeout_value}s) waiting for #{@command.inspect} to find a match using #{wait_value.inspect} in \n'#{log.read}'"
end