cname_lookup and eventlet 0.20

[Romain LE DISEZ]

Behavior: when using eventlet 0.20, if the domain from Host header does not have a CNAME record, the cname_lookup middleware throw an exception, so the user get a 500 error.

With this commit[1] included in eventlet 0.20, eventlet define its own NoAnswer exception (and NXDOMAIN). It seems it is not catched by
    except (DNSException, NXDOMAIN, NoAnswer)
in lookup_cname()

But If I change the except to dns.resolver.NoAnswer it works.

[1] https://github.com/eventlet/eventlet/commit/52b09becacd23f384cf69ae37d70c893c43e3b13

[Romain LE DISEZ (rledisez)]

Proposal: https://review.openstack.org/#/c/435770/

[Tim Burke (1-tim-z)]

Traceback looks something like

Mar 7 18:52:17 saio proxy-server: Error: An error occurred:
Traceback (most recent call last):
  File "/vagrant/swift/swift/common/middleware/catch_errors.py", line 41, in handle_request
    resp = self._app_call(env)
  File "/vagrant/swift/swift/common/wsgi.py", line 1058, in _app_call
    resp = self.app(env, self._start_response)
  File "/vagrant/swift/swift/common/middleware/gatekeeper.py", line 102, in __call__
    return self.app(env, gatekeeper_response)
  File "/vagrant/swift/swift/common/middleware/healthcheck.py", line 52, in __call__
    return self.app(env, start_response)
  File "/vagrant/swift/swift/common/middleware/proxy_logging.py", line 346, in __call__
    six.reraise(exc_type, exc_value, exc_traceback)
  File "/vagrant/swift/swift/common/middleware/proxy_logging.py", line 338, in __call__
    iterable = self.app(env, my_start_response)
  File "/vagrant/swift/swift/common/middleware/copy.py", line 318, in __call__
    return self.app(env, start_response)
  File "/vagrant/swift/swift/common/middleware/cname_lookup.py", line 135, in __call__
    ttl, found_domain = lookup_cname(a_domain)
  File "/vagrant/swift/swift/common/middleware/cname_lookup.py", line 58, in lookup_cname
    answer = dns.resolver.query(domain, 'CNAME').rrset
  File "/usr/local/lib/python2.7/dist-packages/eventlet/support/dns/resolver.py", line 1132, in query
    raise_on_no_answer, source_port)
  File "/usr/local/lib/python2.7/dist-packages/eventlet/support/dns/resolver.py", line 1051, in query
    raise NXDOMAIN(qnames=qnames_to_try, responses=nxdomain_responses)
NXDOMAIN: The DNS query name does not exist: saio.swiftstack.org. (txn: tx96c22536d08d443d94b81-0058bf0161)

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/435770
Committed: https://git.openstack.org/cgit/openstack/swift/commit/?id=d621277feb235e8da2a1e155a21e80f5daf6d892
Submitter: Jenkins
Branch: master

commit d621277feb235e8da2a1e155a21e80f5daf6d892
Author: Romain LE DISEZ <email address hidden>
Date: Sat Feb 18 17:01:08 2017 +0100

    Fix cname_lookup/eventlet 0.20+ DNS exceptions

    Since version 0.20, eventlet bundle a dnspython version (commit:
    52b09becacd23f384cf69ae37d70c893c43e3b13). Since then, catching
    exceptions require the full module path.

    Closes-Bug: #1656891

    Change-Id: Iac6bb974c1a5d084e450057cf5de1eec80ae21a1

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/swift 2.14.0 release.