SFTP Integration

SFTP is the primary file transport protocol for enterprise partners. The platform supports both directions: inbound (we poll and download) and outbound (we push after transform).

Library Choice

Library	Verdict
JSch	Widely used, stable, but unmaintained (use fork com.github.mwiede:jsch)
Apache MINA SSHD	Actively maintained, full SSH2, better for connection pooling — recommended
sshj	Modern, clean API, good alternative

Use Apache MINA SSHD (org.apache.sshd:sshd-sftp). It supports connection multiplexing, key exchange algorithms needed by modern servers, and a proper connection pool abstraction.

Inbound (Download) Flow

Outbound (Send) Flow

Connection Pool Design

• Each SftpConnector owns its pool (max size configurable, default 3)
• Sessions are validated before borrow (send keep-alive / test channel)
• On validation failure: recreate session, re-authenticate
• Pool is torn down when integration is deleted or updated

Authentication Options

Prefer private key auth for production — passwords are susceptible to brute force and rotation is harder.

File Acknowledgement Strategy

Strategy	Config	When to use
Move to /processed	moveToPath: "/archive/processed"	Partner needs to verify delivery
Move to /error	Automatic on pipeline failure	Quarantine bad files
Delete after download	deleteAfterDownload: true	Simplest, no archive needed
Leave in place	Default (no config)	When partner manages cleanup

SFTP Config Example

{
  "name": "Bank ABC Inbound Transactions",
  "type": "SFTP",
  "direction": "INBOUND",
  "config": {
    "host": "sftp.bankabc.com",
    "port": 22,
    "username": "transform_svc",
    "remotePath": "/outbound/transactions/",
    "filePattern": "*.csv",
    "pollIntervalSeconds": 300,
    "moveToPath": "/outbound/transactions/processed",
    "authMethod": "PRIVATE_KEY"
  },
  "credentials": {
    "privateKey": "-----BEGIN RSA PRIVATE KEY-----\n...",
    "passphrase": "optional"
  }
}

warning

The credentials object in the request is write-only. It is encrypted immediately on receipt and never returned in GET responses.