[GitHub] [airflow] mik-laj edited a comment on pull request #13424: Disables reverse IP lookup for environment check

[GitBox <gi...@apache.org>]

mik-laj edited a comment on pull request #13424:
URL: https://github.com/apache/airflow/pull/13424#issuecomment-753386669


   > It looks like there is a race condition with docker compose
   that causes services that started fast enough (before DNS)
   to get a different reverse-DNS IP lookup (usually it is
   just <SERVICE> but sometimes it is
   <DOCKER_COMPOSE_APP>_<SERVICE>_1_<NETWORK>)
   
   ```
     DNS fwd/rev mismatch: rabbitmq != docker-compose_rabbitmq_1.docker-compose_default
     rabbitmq [172.25.0.8] 5672 (amqp) : Connection refused
      sent 0, rcvd 0
   ```
   
   I think we have two separate messages here. The first is a warning that always occurs if one host have multiple DNS names and run netcat in very verbose mode (``-vv``). The second is a real error message that contains information about the problemr that happened.
   
   Take a look at an example.
   ```bash
   $ nc -zvv kdc-server-example-com 88
   DNS fwd/rev mismatch: kdc-server-example-com != docker-compose_kdc-server-example-com_1.example.com
   kdc-server-example-com [10.5.0.2] 88 (kerberos) open
    sent 0, rcvd 0
   $  echo $?
   0
   $ nc -z kdc-server-example-com 88
   $ echo $?
   0
   ```
   This warning does not affect communication in most cases and is only relevant in very restrictive network configurations, e.g. in the case of Kerberos, which tries to validate the message source a little more.
   
   So if we want to improve CI stability, this change will not help us in anything.
   


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