SFTP boundary
01A successful login proves almost nothing about delivery.
SFTP remains a common boundary between organizations because it is simple, secure, and widely supported. Reliability depends on more than opening an SSH session: directory ownership, host identity, file visibility, naming, late arrival, and cleanup define the real exchange contract.
Trust the host, then the path
Define the trusted host identity, remote directory, file pattern, recursion, permissions, expected ownership, and arrival rule. Avoid letting a broad directory listing turn unrelated partner files into work.
Assume sessions can break
Network sessions can end mid-transfer. Decide whether partial remote files are hidden, renamed, resumed, replaced, or quarantined and how a retry proves that an already delivered file is not duplicated.
Define the partner handshake
Agree on temporary and final names, atomic handoff, timestamps, archive location, retention, acknowledgements, deletion rights, and late-file handling with the partner that owns the other side.
File-aware Flower route
02Use file state, not elapsed time, to decide what is ready.
Flower's SFTP endpoint can list and stat remote entries, stream or range-read files, create paths, upload, and use standard or POSIX rename. The flow combines those primitives with classification, validation, tracking, and controlled retry.
Discover only owned files
Directory, recursion, glob, age, size, and final-name rules define the candidate set. Flower can reject unrelated partner files before opening content and keep late arrivals visible without broad rescans.
Publish with rename
Write under a temporary name, close and validate the file, then rename to the agreed final name when the server's semantics support it. Consumers never need to infer completeness from a quiet period.
Restart at a known boundary
After disconnect, Flower reconciles remote size, name, destination evidence, and prior tracking before retry. Partial output is resumed only when the contract supports it; otherwise it is replaced or quarantined deliberately.
Partner operations
03Write the exchange contract for humans and machines.
SFTP estates are heterogeneous: servers expose different rename extensions, permissions, limits, time zones, and housekeeping. A dependable exchange records what was agreed instead of relying on tribal knowledge.
Host-key lifecycle
Pin the expected host key through a managed known-hosts process. Define key rotation, emergency change approval, account rotation, least directory permissions, and an alert path; password success alone is not server authentication.
Naming and calendar
Document temporary and final patterns, business date, time zone, expected window, late-file cutoff, duplicate suffixes, empty-file meaning, acknowledgements, archive layout, and retention. These rules are the real API.
Server limits and observability
Benchmark packet size and file concurrency against the partner server, then cap them. Track connection time, listing latency, transfer rate, remote errors, file age, backlog, retries, and quarantine so a slow partner is visible before the SLA fails.