(maint) Avoid deadlock of Facter::Core::Execution.execute

Author: Oana Tanasoiu

acceptance/tests/custom_facts/long_stderr_with_time_limit.rb

@@ -0,0 +1,34 @@
+test_name "Facter::Core::Execution doesn't kill process with long stderr message" do
+  tag 'risk:high'
+
+  confine :except, :platform => /windows/
+
+  long_output = "This is a very long error message. " * 4096
+  file_content = <<-EOM
+   #!/bin/sh
+   echo 'newfact=value_of_fact'
+   1>&2 echo #{long_output}
+   exit 1
+  EOM
+
+
+  agents.each do |agent|
+
+    external_dir = agent.tmpdir('external_dir')
+    fact_file = File.join(external_dir, 'test.sh')
+    create_remote_file(agent, fact_file, file_content)
+    agent.chmod('+x', fact_file)
+
+    teardown do
+      agent.rm_rf(external_dir)
+    end
+
+    step "Facter: should resolve the external fact and print as warning script's stderr message" do
+      on agent, facter('--external-dir', external_dir, 'newfact') do |facter_output|
+        assert_match(/value_of_fact/, facter_output.stdout.chomp)
+        assert_match(/WARN test.sh .*test.sh resulted with the following stderr message: This is a very long error message./, facter_output.stderr.chomp)
+      end
+    end
+  end
+end
+

lib/facter/custom_facts/core/execution/base.rb

@@ -100,18 +100,22 @@ def execute_command(command, on_fail, logger = nil, time_limit = nil)
             @log.debug("Executing command: #{command}")
             out, stderr = Open3.popen3(opts, command.to_s) do |_, stdout, stderr, wait_thr|
               pid = wait_thr.pid
-              output = +''
-              err = +''
+              stdout_messages = +''
+              stderr_messages = +''
+              out_reader = Thread.new { stdout.read }
+              err_reader = Thread.new { stderr.read }
               begin
                 Timeout.timeout(time_limit) do
-                  output << stdout.read
-                  err << stderr.read
+                  stdout_messages << out_reader.value
+                  stderr_messages << err_reader.value
                 end
               rescue Timeout::Error
                 @log.debug("Timeout encounter after #{time_limit}s, killing process with pid: #{pid}")
                 Process.kill('KILL', pid)
+                out_reader.kill
+                err_reader.kill
               end
-              [output, err]
+              [stdout_messages, stderr_messages]
             end
             log_stderr(stderr, command, logger)
           rescue StandardError => e