[jira] [Created] (NIFI-10221) Nifi does not respect multirecord domain in hostname field.

["Wiktor Kubicki (Jira)" <ji...@apache.org>]

Wiktor Kubicki created NIFI-10221:
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             Summary: Nifi does not respect multirecord domain in hostname field.
                 Key: NIFI-10221
                 URL: https://issues.apache.org/jira/browse/NIFI-10221
             Project: Apache NiFi
          Issue Type: Bug
    Affects Versions: 1.16.0
            Reporter: Wiktor Kubicki


*Short description:*

Using DNS we are able to add multiple A records with several IP addresses to domain, but Nifi use always only (first?) one.

 

*Background:*

We can add multiple A records in DNS to provide round robin "load balancer", which can also be used as failover server in Active - Active server schema. A good example of that implementation is there: [How To Configure DNS Round-Robin Load-Balancing For High-Availability | DigitalOcean|https://www.digitalocean.com/community/tutorials/how-to-configure-dns-round-robin-load-balancing-for-high-availability].

We use this solution to provide address to our two sFTP servers in  different geographical locations.

 

{*}How it works now{*}:

When i put domain into hostname field in listSFTP, Nifi will solve DNS and obtain only one address (probably the first one but i cannot comfirm) and connect to it. But when this one IP is unreachable, NiFi will not try with second one nor try the second one in any next run.

 

*How it should works:*

Addresses should be used randomly (round robin), and if one is unavailable, then in the same run should be tried another one till end of IP's or successful connection.

 

{*}Example{*}:

Using sftp client (OpenSSH_7.4p1, OpenSSL 1.0.2k-fips  26 Jan 2017) i can connect to host by domain, even if one of IP addresses is down:

 
{code:java}
$ sftp -vvv -oPort=22 user@example.com
OpenSSH_7.4p1, OpenSSL 1.0.2k-fips  26 Jan 2017
debug1: Reading configuration data /XXX/.ssh/config
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 58: Applying options for *
debug2: resolving "example.com" port 22
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to example.com [X.X.X.203] port 22.
debug1: connect to address X.X.X.203 port 22: Connection refused
debug1: Connecting to example.com [Y.Y.Y.123] port 22.
debug1: Connection established.{code}
As you can see, sftp tries to connect to first, when connections refused then it try to second one with success. And that's how it should work in NiFi

 



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