Uncatchable crash if ping command not available - returns "spawn ping ENOENT"

[kevinburkenotion]

See 3rd-Eden#342 for the original, the same issue exists in this fork. I've repasted the contents below.

If you get in a state where memcached attempts to reconnect, it will call ping(this.tokens[1]), which attempts to spawn a binary to call ping -c 3. The ping function in Javascript does not handle the case where the ping binary is not present - specifically it's missing an .on(error) handler that could catch the situation where ping is not found, has the wrong permissions, or the running process does not have permission to spawn children.

function ping (host, callback) {
  var isWin = process.platform.indexOf('win') === 0; // win32 or win64
  var arg = isWin ? '-n' : '-c';
  var pong = spawn('ping', [arg, '3', host]); // only ping 3 times

  pong.stdout.on('data', function stdoutdata (data) {
    callback(false, data.toString().split('\n')[0].substr(14));
    pong.kill();
  });

  pong.stderr.on('data', function stderrdata (data) {
    callback(new Error(data.toString().split('\n')[0].substr(14)), false);
    pong.kill();
  });
}

The lack of a .on('error') handler means that any failure here is uncatchable and crashes the process.

More broadly I have to wonder about the effectiveness of calling ping if a connection fails - it's not clear that one TCP packet is going to have any more luck than another if the connection is in trouble.