NATS

The NATS output publishes messages to a NATS server, either to a regular subject or to a JetStream stream. It supports optional username/password or token authentication.

Configuration

Field	Type	Required	Default	Description
type	string	yes	—	Fixed value "nats"
url	string	yes	—	NATS server URL (e.g. nats://localhost:4222).
mode	object	yes	—	Publishing mode (see below).
auth	object	no	—	Authentication configuration (see below).
value_field	string	no	—	Binary or string column whose per-row value becomes that message's payload (a null value or a missing column is an error). When unset, the codec encoding of the batch applies.

mode

mode is a tagged object (selected by its type field).

Field	Type	Required	Default	Description
type	string	yes	—	regular or jet_stream.
subject	object	yes	—	NATS subject to publish to (expression; see below).

subject (Expr<String>)

Field	Type	Required	Description
type	string	yes	value (static) or expr (SQL expression).
value	string	yes (value)	Static subject name.
expr	string	yes (expr)	SQL expression evaluated per message.

An expression must yield a non-null string for every row: a NULL result for any row fails the batch with the expression and the row named (wrap it in COALESCE(expr, 'fallback') or filter such rows upstream).

auth

Field	Type	Required	Default	Description
username	string	no	—	Username (use with password).
password	string	no	—	Password (use with username).
token	string	no	—	Authentication token.

Only one of username/password or token should be configured; if both are present, username/password takes precedence.

Examples

Regular subject with username/password

yaml

output:
  type: "nats"
  url: "nats://localhost:4222"
  mode:
    type: "regular"
    subject:
      type: "expr"
      expr: "concat('orders.', id)"
  auth:
    username: "user"
    password: "pass"
  value_field: "message"

JetStream with token

yaml

output:
  type: "nats"
  url: "nats://localhost:4222"
  mode:
    type: "jet_stream"
    subject:
      type: "value"
      value: "orders.new"
  auth:
    token: "secret-token"

TLS

Use a tls:// URL scheme to connect over TLS (for example tls://nats.example.com:4422); async-nats negotiates TLS natively for tls:// URLs and requires the server to support TLS.