[NIFI-9507] FetchSFTP spawns multiple keep-alive threads on failed connections

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.12.0, 1.15.1
• Fix Version/s: 1.16.0, 1.15.2
• Component/s: Extensions
• Assignee: David Handermann
• Reporter: David Handermann
• Created: 20/Dec/21 16:24
• Updated: 04/Jan/22 16:40
• Resolved: 21/Dec/21 03:24

Description

The FetchSFTP processor relies on the shared SFTPTransfer class to handle SFTP communication using the SSHJ library starting in NiFi 1.12.0.  The SFTPTransfer class instantiates and configures an SSHClient based on processor properties, calling the connect method after initial configuration.

The SSHClient.connect method can throw an IOException on failure to reach the remote SFTP server, but the NiFi SFTPTransfer class does not close in the SSHClient.  Although FetchSFTP catches the IOException in the parent FetchFileTransfer.onTrigger method, the processor never closes the failed SSHClient because SFTPTransfer never assigned the instance variable.

The creation and lifecycle of the SSHClient inside SFTPTransfer should be adjusted to ensure closure of SSHClient and the associated keep-alive thread.

Issue Links

• is related to: NIFI-7443 SFTP KeepAlive not working
• links to: GitHub Pull Request #5617