dns.setServers() crash

[BLeQuerrec]

Hi,

In a Vagrant Ubuntu environment, io.js crashes with this code:

$ cat dns.js
var dns = require('dns');

dns.resolveSoa('example.org', function(err, soa){
    console.log(soa.nsname);
    dns.resolve4(soa.nsname, function (err, nameServers) {
        console.log(dns.getServers());
        dns.setServers(nameServers);
        console.log(dns.getServers());
    });
});

Expected result:

$ iojs dns.js
sns.dns.icann.org
[ '10.0.2.3' ]
[ '199.4.28.26' ]

Actual result:

$ iojs dns.js
sns.dns.icann.org
[ '10.0.2.3' ]
iojs: ../deps/cares/src/ares_destroy.c:102: ares__destroy_servers_state: Assertion `ares__is_list_empty(&server->queries_to_server)' failed.
Aborted (core dumped)

Other informations:

$ cat /etc/os-release
NAME="Ubuntu"
VERSION="14.04.1 LTS, Trusty Tahr"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 14.04.1 LTS"
VERSION_ID="14.04"
HOME_URL="http://www.ubuntu.com/"
SUPPORT_URL="http://help.ubuntu.com/"
BUG_REPORT_URL="http://bugs.launchpad.net/ubuntu/"
$ iojs -v
v1.2.0

DNS test (in test/simple/test-dns.js) ends successfully. This bug can be fixed by removing line 102 in deps/cares/src/ares_destroy.c.
Node.js bug: nodejs/node-v0.x-archive#9243

[tellnes]

I'm seeing similar results on os x 10.9.5

$ iojs dns.js
sns.dns.icann.org
[ '10.0.0.1' ]
Assertion failed: (ares__is_list_empty(&server->queries_to_server)), function ares__destroy_servers_state, file ../deps/cares/src/ares_destroy.c, line 102.
Abort trap: 6

[rvagg]

@iojs/tc can someone qualified jump on this? otherwise it'll have to go in to "known issues" in 1.3.0.

[indutny]

Will do.

[indutny]

I have two solutions to the problem:

• cares: fix set_servers during active queries #899
• throw in JS if there is any active queries
• wait until query completion before changing the servers

What do you think will be most preferable? cc @bnoordhuis

[silverwind]

wait until query completion before changing the servers

Would that block new queries from using the updated servers until all outstanding requests finish? If so, any way to have setServers apply for all following queries?

[tellnes]

The best solution would be that queries created before calling setServers is using the old servers while queries created after calling setServers is using the new servers.

If I understand your solutions correctly, that would mean wait until query completion and queue up new queries.

[silverwind]

Meant what @tellnes said. If that's possible, there's no need to throw.

[indutny]

Good suggestion. I'll see what I can do.