shell command stalls if command produces lots of output

[youngm]

https://github.com/cloudfoundry/java-buildpack/blob/master/lib/java_buildpack/util/shell.rb

In a buildpack customization, I execute a shell command that produces a lot of stdout/stderr. When I do the buildpack staging stalls. It appears this is happening because the thread will stall if it cannot write all output to stdout and stderr.

This doesn't appear to affect other buildpack commands because the stdout/stderr buffers are large enough to hold all their command output.

Changing the implementation to the following worked around my problem:

        Open3.popen3(*args) do |_stdin, stdout, stderr, wait_thr|
          stdout = stdout.gets nil
          stderr = stderr.gets nil
          unless wait_thr.value.success?
            puts "\nCommand '#{args.join ' '}' has failed"
            puts "STDOUT: #{stdout}"
            puts "STDERR: #{stderr}"

            raise
          end
        end