Test an FTP server

FTP_PASSWORD=secret vegaload run -vus 4 -duration 10s -protocol ftp \
  -target ftp://localhost -opt mode=roundtrip -opt path=/upload/vl-{id}.bin \
  -opt size=1MiB -opt allow_writes=true -opt username=vegaload \
  -opt password_env=FTP_PASSWORD

-target is ftp://host (port 21, or 990 with -opt tls=implicit) or ftps://host (implicit TLS, port 990). A port in the URL always wins. vegaload doctor takes no -opt, so it reads only the URL: it checks port 21 for ftp://host. To check port 990, give it ftps://host or ftp://host:990. Put the password in an environment variable. Do not put it in the URL. With no username and no password_env, the client logs in as anonymous with the password vegaload@. A username other than anonymous needs password_env. tls=explicit on ftp:// is AUTH TLS. tls=none is not allowed with ftps://. -insecure skips certificate checks for a test server.

-opt keys:

Key	Default	Meaning
`mode`	`download`	`connect`, `download`, `upload`, `list`, `stat`, `delete`, `roundtrip`
`path`		The file or directory. `{id}` is replaced in the path and in a body.
`size`		Upload this many bytes (`1KiB`, `1MiB`, up to 4GiB) instead of a body. `size=0` is an empty file.
`fill`	`random`	`random`, `zero` or `text`, used with `size`.
`expect_size`		Download must be exactly this many bytes.
`expect_sha256`		Download must hash to this SHA-256 (64 hex characters).
`expect`		Text the download must contain, searched in the first 1MiB, or a name the listing must contain.
`limit`	`1000`	How many listing entries the reply keeps (1 to 100000).
`hidden`	false	For `list` only: send `LIST -a`. MLSD already returns names that start with `.`.
`username`	`anonymous`	Login name.
`password_env`		Environment variable that holds the password.
`tls`	from the URL	`none`, `explicit` or `implicit`. With `implicit` and no port in the URL, the port is 990.
`tls_verify`	true	Check the server certificate. `-insecure` turns this off.
`tls_max`	`1.2`	Highest TLS version, `1.2` or `1.3`. It is `1.2` because vsftpd 3.0.5 fails large uploads over TLS 1.3 (`426 Failure reading network stream`). Use `1.3` for a server that needs it.
`ca_file`, `cert_file`, `key_file`, `tls_server_name`		See TLS with your own CA.
`sessions`	`10`	How many control connections this run may hold. Match it to `-vus`. Extra users wait.
`connection`	`shared`	`per_call` dials a new session and drops it. It still takes one of the `sessions` slots, so the number in flight stays bounded.
`data_host`	`control`	`control` dials the data connection to the host you named. `announced` uses the PASV address, which must be an IP.
`epsv`	`auto`	`off` uses PASV only.
`allow_writes`	false	Required for `upload`, `roundtrip` and `delete`.
`allow_admin`	false	Also required for `delete`, and for an `upload` whose path has no `{id}`. Needs `allow_writes` as well.

Transfers are passive and binary. There is no active mode, no ASCII mode, no resume and no recursion. One server per run.
connect logs in and does nothing else. download reads one file. upload writes one file. list lists one directory. stat asks for the size. delete removes one file. roundtrip uploads, downloads, checks the bytes and deletes that file. It needs {id} in the path, so it never removes a file that was already there.
sessions is how many control connections the run may hold at once. Set it to the same number as -vus, or extra users wait for a free session. A session that the server closes is not reused. The next call dials again. There is no hidden retry.
{id} in a path or a body becomes a new value on every call. It is not written into the bytes that size generates.
An upload without size and without a body is an error. A failed upload can leave a partial file. roundtrip still tries to delete its file. If that delete fails, the call can still pass and the text names the file that is left. A call that the end of the run cuts off can also leave its file, at most one per user. Use a scratch directory.
The account is the real lock. allow_writes and allow_admin only stop VegaLoad from sending the command. Give the account a scratch directory.
A listing skips lines the client cannot parse. limit trims what the reply returns. The client still reads the whole listing first, so a huge directory uses memory for every name. Many servers expand a wildcard in a list path. hidden changes LIST only.
data_host=control ignores the address in the PASV reply and dials the host from -target. Use that when the server is behind NAT and announces an address the client cannot reach. data_host=announced dials the announced IP. A firewall must allow the passive port range.
The timeout covers the whole call, including the transfer. A call that takes too long says timed out after <duration>. Throughput in the report is the bytes of the call divided by the time the call took.
A script's ftp reply has entries (each name, type, size and time), size, total, timing (connectMs, loginMs, transferMs, uploadMs, downloadMs, deleteMs) and text. time is UTC, such as 2020-01-02T15:04:05Z, or "" when the server gave none. Give the password as password: env.FTP_PASSWORD.
The host allowlist and caps apply as for HTTP targets.