question Re: Apache NiFi 2.6.0/2.7.2 ListSFTP Hostname not working when using Proxy Configuration Service. in Support Questions

Apache NiFi 2.6.0/2.7.2 ListSFTP Hostname not working when using Proxy Configuration Service.

NSX — Fri, 09 Jan 2026 19:23:31 GMT

Apache NiFi 2.6.0/2.7.2 ListSFTP Hostname not working when using Proxy Configuration Service. It works when an IP address is listed.

Example:
Hostname: cloudera.com
Port: 22
Proxy Configuration Service: StandardProxyConfigurationService (Proxy Type=HTTP)

When executed (run once), it gets the following error:
ListSFTP[id=a423ae96-019b-1000-c5c2-8e609a342bc5] Processing failed: org.apache.nifi.processors.standard.socket.ClientConnectException: SSH Connection failed [cloudera.com:22]
- Caused by: org.apache.sshd.common.SshException: DefaultConnectFuture[A@cloudera.com/<unresolved>:22]: Failed (UnknownHostException) to execute: cloudera.com
- Caused by: java.net.UnknownHostException: cloudera.com

When using the IP address of cloudera.com as 151.101.127.10 will work (disregard the proxy 403 error as it is not white listed)
ListSFTP[id=a423ae96-019b-1000-c5c2-8e609a342bc5] Processing failed: org.apache.nifi.processors.standard.socket.ClientAuthenticationException: SSH Authentication failed [151.101.127.10:22]
- Caused by: org.apache.sshd.common.SshException: [ssh-connection]: Failed (HttpProxyConnectException) to execute: http, none, proxy.*****.**/xxx.xx.xx.xxx:8080 => /151.101.127.10:22, status: 403 Forbidden
- Caused by: io.netty.handler.proxy.HttpProxyHandler$HttpProxyConnectException: http, none, proxy.*****.**/xxx.xx.xx.xxx:8080 => /151.101.127.10:22, status: 403 Forbidden

When the above is executed under NiFi 1.26.0 works fine with hostname or IP address when using the proxy.

Anyone have seen this issue?

Please advise.

Re: Apache NiFi 2.6.0/2.7.2 ListSFTP Hostname not working when using Proxy Configuration Service.

VidyaSargur — Mon, 12 Jan 2026 06:00:52 GMT

@NSX, Welcome to our community! To help you get the best possible answer, I have tagged in our NiFi experts @MattWho @haridjh @vats who may be able to assist you further.

Please feel free to provide any additional information or details about your query, and we hope that you will find a satisfactory solution to your question.

Re: Apache NiFi 2.6.0/2.7.2 ListSFTP Hostname not working when using Proxy Configuration Service.

MattWho — Mon, 12 Jan 2026 13:34:03 GMT

@NSX

Caused by: java.net.UnknownHostException: cloudera.com

Above is telling you that your Apache NIFi 2.6.0 /2.7.2 server is unable to resolve "cloudera.com to an IP address. You Apache NiFi 1.26 must be successful in hostname resolution and thus working.

What if you manually added following to your hosts file on your 2.7.2 servers?
151.101.127.10 cloudera.com

Have you tried pinging cloudera.com from both your 2.7.2 and 1.26 servers?

Please help our community grow. If you found any of the suggestions/solutions provided helped you with solving your issue or answering your question, please take a moment to login and click "Accept as Solution" on one or more of them that helped.

Thank you,
Matt

Re: Apache NiFi 2.6.0/2.7.2 ListSFTP Hostname not working when using Proxy Configuration Service.

NSX — Mon, 12 Jan 2026 14:06:20 GMT

@MattWho

Server under 1.26.0 and 2.7.2 are behind the firewall. Both servers were in the same subnet. After we upgraded one of the server from 1.26.0 to 2.6.0 then 2.7.2 having issue using the Proxy Configuration service (Proxy server) to reach the internet ie: cloudera.com.

$ curl -x http://proxy.xxxx.ca:8080 sftp://cloudera.com:22 -v
* Trying xxx.xx.xx.xxx:8080...
* Connected to proxy.xxxx.ca (xxx.xx.xx.xxx) port 8080 (#0)
* allocate connect buffer!
* Establish HTTP proxy tunnel to cloudera.com:22
> CONNECT cloudera.com:22 HTTP/1.1
> Host: cloudera.com:22
> User-Agent: curl/7.76.1
> Proxy-Connection: Keep-Alive
>
< HTTP/1.1 403 Forbidden
< Cache-Control: no-cache
< X-XSS-Protection: 1
< Connection: Keep-Alive
< Content-Type: text/html; charset=utf-8
< Content-Length: 729
< Pragma: no-cache
<
* Received HTTP code 403 from proxy after CONNECT
* CONNECT phase completed!
* Closing connection 0
curl: (56) Received HTTP code 403 from proxy after CONNECT

Disregard the proxy 403 error as it cloudera.com is not listed in the proxy white list.

The OS curl connection is working so it is not related to the host file (we cant use it behind the firewall). In NiFi 1.26.0 works fine. The server upgraded to 2.6.0/2.7.2 was 1.26.0 previously and didnt have this issue. Seems to be a bug with 2.x.

If we use IP address in NiFi, the ListSFTP will work but not when using the hostname ie: cloudera.com; seems to be an issue passing the hostname to the proxy.

DefaultConnectFuture[A@cloudera.com/<unresolved>:22]: Failed (UnknownHostException) to execute: cloudera.com

Please advise.

Re: Apache NiFi 2.6.0/2.7.2 ListSFTP Hostname not working when using Proxy Configuration Service.

haridjh — Tue, 20 Jan 2026 14:30:42 GMT

@NSX
As stated previously, have you tried pinging cloudera.com from 2.6.0/2.7.2 server.

Re: Apache NiFi 2.6.0/2.7.2 ListSFTP Hostname not working when using Proxy Configuration Service.

NSX — Tue, 20 Jan 2026 14:51:06 GMT

Pinging directly will not work as it is behind the firewall. We need to use curl pointing to the proxy to connect to cloudera.com at the OS level (could be any internet hostname)

My previous responses tested using curl calling our proxy server at the OS level where NiFi is running and it is working.

Only NiFi using Configuration service (Proxy server: HTTP) seems to broken with 2.7.2. Before the upgrade from 1.26 to 2.7.2, NiFi worked connecting to cloudera using our own proxy server.

Re: Apache NiFi 2.6.0/2.7.2 ListSFTP Hostname not working when using Proxy Configuration Service.

NSX — Wed, 03 Jun 2026 12:29:22 GMT

ListSFTP[id=7b88bae5-5932-3efb-d1ad-44d1835a4d36] Processing failed: org.apache.nifi.processors.standard.socket.ClientConnectException: SSH Connection failed [sftp.uber.com:2222]
- Caused by: org.apache.sshd.common.SshException: DefaultConnectFuture[82d495ce@sftp.uber.com/<unresolved>:2222]: Failed (UnknownHostException) to execute: sftp.uber.com
- Caused by: java.net.UnknownHostException: sftp.uber.com

No issues with NiFi 1.26!

Updated to the latest 2.9.0 still the same issue. Anyone?

Re: Apache NiFi 2.6.0/2.7.2 ListSFTP Hostname not working when using Proxy Configuration Service.

NSX — Fri, 12 Jun 2026 13:11:21 GMT

I wanted to add that when using the IP address:104.36.197.137 of sftp.uber.com it worked with NiFi 2.9.0 using PROXY HTTP Configuration service.

It has nothing to do with the OS DNS resolution because it is connected to the proxy server to resolve the destination.

When using sftp.uber.com, NiFi PROXY HTTP configuration service, it never reached the proxy server at all from the Proxy trace debug. It has to be a NiFi PROXY configuration resolution with hostname when it works with 1.2x and not 2.x.

Re: Apache NiFi 2.6.0/2.7.2 ListSFTP Hostname not working when using Proxy Configuration Service.

alightmotion — Sat, 11 Jul 2026 08:57:24 GMT

Thanks for the suggestions, Matt.

That's a good point about the hostname resolution happening before the proxy connection. I haven't tried adding the hostname to the hosts file yet, so I'll test that next.

I'll also compare the ping and nslookup results on both the NiFi 1.26.0 and 2.7.2 servers to see if there's any difference in DNS resolution. If the hostname resolves correctly but the issue still occurs only in 2.7.2, it may point to a regression in the newer version's handling of proxy or DNS resolution.

I'll update the thread once I have the results. Thanks again!