Mapp Engage can transfer files using SFTP. Files can be transferred to either of the following:
A Mapp-provided SFTP account
An external SFTP account
Please note that Mapp Engage does not support file transfers via FTP or FTPS.
How Mapp Engage transfers files by SFTP
Mapp Engage may use multiple SFTP sessions to complete a file upload. These sessions can include:
A connection to check whether the remote folder exists and is writable
A connection to transfer the file to the remote server using a unique temporary filename
A connection to verify that the file was transferred successfully and rename it to its final filename
When Mapp Engage uploads or downloads a file, it temporarily renames the file by appending a unique extension. This extension includes the upload process ID of the current Mapp Engage server.
After the transfer is complete and verified, Mapp Engage removes the temporary extension and renames the file to its final filename.
This temporary naming process prevents processing collisions. Files can be large and may take time to transfer. Without a temporary filename, Mapp Engage or an external client process could detect and start processing a file before the transfer is complete.
Compatibility issue with write-once SFTP servers
Some high-security external SFTP servers use a “write once” process. In this configuration, a file is moved away from the upload folder immediately after it is written or after the transfer session disconnects.
This behavior can cause Mapp Engage file transfers to fail.
Mapp Engage expects the transferred file to remain in the upload folder until the transfer checks and final rename are complete. If the external SFTP server moves the file immediately, Mapp Engage can no longer find the file in the expected location. As a result, the verification step or final rename fails.
Recommended configuration
For external SFTP servers, configure the server or downstream process to wait several minutes before moving files from the upload folder. This delay gives Mapp Engage enough time to complete the transfer verification and final rename.
If the external SFTP server cannot support this delay, use a Mapp-provided and Mapp-managed SFTP account instead. Mapp-managed SFTP accounts support the required transfer, verification, and rename process.