[THRIFT-3848] As an implementer of a perl socket server, I do not want to have to remember to ignore SIGCHLD for it to work properly

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.8, 0.9, 0.9.1, 0.9.2, 0.9.3
• Fix Version/s: 0.10.0
• Component/s: Perl - Library

Environment

Ubuntu 14.04, perl forking server, C++ client

• Assignee: James E. King III
• Reporter: James E. King III
• Created: 02/Jun/16 16:15
• Updated: 02/Feb/17 18:12
• Resolved: 17/Jul/16 16:10

Description

In a project I work on, we use a perl thrift server as a mock to simulate something in production. A C++ client connects, makes a call, and disconnects. The perl server is a forking server.

I found that if I do not explicity ignore SIGCHLD, I can accept one connection and process it, but when it disconnects, the subsequent accept call is interrupted by a SIGCHLD and results in a useless handle that can_read says cannot be read. This puts Server.pm into an infinite accept/read/fail loop. The serve() method of the ForkingServer needs to explicitly ignore SIGCHLD to work properly.

I've observed this behavior as far back as thrift-0.8.0 up through 0.9.3.

The workaround is to add the following code before calling serve():

$SIG{CHLD} = 'IGNORE';

Issue Links

• breaks: THRIFT-4065 Document Perl ForkingServer signal restriction imposed by THRIFT-3848 and remove unnecessary code
• links to: GitHub Pull Request #1040