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module Tork
# Wrapper for IO.popen() that automatically re-establishes itself
# whenever the child process terminates extraneously, on its own.
class Bridge
def initialize command
@command = command
connect
end
def disconnect
return unless @guardian.alive?
# prevent guardian from reconnecting bridge while we disconnect it
@guardian.exit
# this should be enough to stop programs that use Tork::Server#loop
# because their IO.select() loop terminates on the closing of STDIN
@io.close_write
# but some programs like tork-herald(1) need to be killed explicitly
# because they do not follow our convention of exiting on STDIN close
Process.kill :SIGTERM, @io.pid
Process.waitpid @io.pid
# this will block until the child process has exited so we must kill it
# explicitly (as above) to ensure that this program does not hang here
@io.close_read
rescue IOError, SystemCallError
# IOError happens if the child process' pipes are already closed
# SystemCallError happens if the child process is already dead
end
def reconnect
disconnect
connect
end
# Allows this object to be passed directly
# into IO.select() and Tork::Server#tell().
def to_io
@io
end
# Allows this object to be treated as IO.
def method_missing *args, &block
@io.__send__ *args, &block
end
private
def connect
@io = IO.popen(@command, 'r+')
# automatically reconnect the bridge when the child process terminates
@guardian = Thread.new do
Process.waitpid @io.pid
warn "#{$0}: repairing collapsed bridge: #{@command} #{$?}"
sleep 1 # avoid spamming the CPU by waiting a bit before reconnecting
connect # no need to disconnect because child process is already dead
end
end
end
end
Version data entries
13 entries across 13 versions & 1 rubygems