gitlab-org--gitlab-foss/lib/gitlab/popen.rb
Stan Hu fd392cd725 Avoid process deadlock in popen by consuming input pipes
A process that spews a lot of output to stderr or stdout could stall out
due to the pipe buffer being full. As described in https://bugs.ruby-lang.org/issues/9082,
we can use the trick used in Ruby's capture3 function to read the pipes in separate
threads.

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/6895
2018-07-12 16:21:30 -07:00

53 lines
1.5 KiB
Ruby

require 'fileutils'
require 'open3'
module Gitlab
module Popen
extend self
Result = Struct.new(:cmd, :stdout, :stderr, :status, :duration)
# Returns [stdout + stderr, status]
def popen(cmd, path = nil, vars = {}, &block)
result = popen_with_detail(cmd, path, vars, &block)
[result.stdout << result.stderr, result.status&.exitstatus]
end
# Returns Result
def popen_with_detail(cmd, path = nil, vars = {})
unless cmd.is_a?(Array)
raise "System commands must be given as an array of strings"
end
path ||= Dir.pwd
vars['PWD'] = path
options = { chdir: path }
unless File.directory?(path)
FileUtils.mkdir_p(path)
end
cmd_stdout = ''
cmd_stderr = ''
cmd_status = nil
start = Time.now
Open3.popen3(vars, *cmd, options) do |stdin, stdout, stderr, wait_thr|
# stderr and stdout pipes can block if stderr/stdout aren't drained: https://bugs.ruby-lang.org/issues/9082
# Mimic what Ruby does with capture3: https://github.com/ruby/ruby/blob/1ec544695fa02d714180ef9c34e755027b6a2103/lib/open3.rb#L257-L273
out_reader = Thread.new { stdout.read }
err_reader = Thread.new { stderr.read }
yield(stdin) if block_given?
stdin.close
cmd_stdout = out_reader.value
cmd_stderr = err_reader.value
cmd_status = wait_thr.value
end
Result.new(cmd, cmd_stdout, cmd_stderr, cmd_status, Time.now - start)
end
end
end