Source Properties by Connector

Reference for all properties available in the from block when reading from each connector type. Every from block shares a set of universal attributes; the sections below document what operation means for each connector and what input.* variables are available in transforms.

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Universal Attributes

Available on every from block regardless of connector type:

Attribute	Type	Required	Description
connector	string	yes	Name of the source connector
operation	string	yes	Event type or endpoint (meaning varies per connector — see below)
format	string	no	Input format: json, xml, csv (default: json)
filter	string/block	no	CEL condition to skip non-matching events

Filter (block form — message queues)

from {
  connector = "rabbit"
  operation = "payments"

  filter {
    condition   = "input.amount > 0"
    on_reject   = "requeue"    # "ack" (discard), "reject" (DLQ), "requeue" (retry)
    id_field    = "input.payment_id"
    max_requeue = 3
  }
}

Schedule trigger (when)

Any flow can add a when block (cron) instead of an event-based from:

flow "nightly_sync" {
  when {
    schedule = "0 0 * * *"    # Standard cron expression
    timezone = "UTC"
  }
  to { ... }
}

---

REST Server

Property	Value
Connector type	rest
operation format	"METHOD /path" — e.g., "GET /users", "POST /orders", "GET /users/:id"

Path parameters use colon syntax (:id, :user_id).

input.* variables

Variable	Source	Description
input.<param>	Path	Path parameters by name (input.id, input.user_id)
input.<param>	Query	Query string parameters by name (input.page, input.limit)
input.<field>	Body	JSON/XML body fields merged directly (POST/PUT/PATCH)
input.headers	Headers	Map of all request headers (lowercased keys)
input.<field>	Multipart	File uploads: {filename, size, content_type, data} (base64)

from {
  connector = "api"
  operation = "POST /users/:id/upload"
}

# Available: input.id (path), input.name (body), input.headers (map), input.avatar (file)

---

GraphQL Server

Property	Value
Connector type	graphql
operation format	"Query.fieldName", "Mutation.fieldName", "Subscription.fieldName"

input.* variables

Variable	Source	Description
input.<arg>	Arguments	GraphQL arguments passed to the field resolver

from {
  connector = "gql"
  operation = "Mutation.createUser"
}

# Available: input.name, input.email (from mutation arguments)

---

gRPC Server

Property	Value
Connector type	grpc
operation format	"Service/Method" or "package.Service/Method"

input.* variables

Variable	Source	Description
input.<field>	Proto message	All protobuf message fields (decoded via JSON)

from {
  connector = "grpc_server"
  operation = "UserService/CreateUser"
}

# Available: input.name, input.email (from proto request message)

---

SOAP Server

Property	Value
Connector type	soap (with driver = "server")
operation format	SOAP operation name — e.g., "CreateOrder", "GetUser"

Extracted from the SOAP envelope body element name.

input.* variables

Variable	Source	Description
input.<field>	SOAP body	Parameters parsed from the SOAP envelope body

from {
  connector = "soap_server"
  operation = "CreateOrder"
}

# Available: input.customer_id, input.items (from SOAP body elements)

---

TCP Server

Property	Value
Connector type	tcp
operation format	Message type string (json/msgpack) or NestJS pattern string

input.* variables

Variable	Source	Description
input.<field>	Message data	All fields from msg.Data merged directly

from {
  connector = "tcp_server"
  operation = "create_order"
}

# Available: input.product_id, input.quantity (from message data)

---

RabbitMQ

Property	Value
Connector type	queue (with driver = "rabbitmq")
operation format	Routing key — e.g., "orders.created", "user.*", "#"

Supports AMQP topic exchange patterns: * matches one word, # matches zero or more.

input.* variables

Variable	Source	Description
input.body	Payload	Parsed JSON (or raw string)
input.headers	AMQP	AMQP headers as map
input.properties	AMQP	Message properties (see below)
input.routing_key	AMQP	The routing key
input.exchange	AMQP	The exchange name

input.properties fields: message_id, correlation_id, content_type, content_encoding, delivery_mode, priority, reply_to, expiration, type, user_id, app_id, timestamp, delivery_tag, redelivered.

from {
  connector = "rabbit"
  operation = "orders.created"
}

# Available: input.body.order_id, input.routing_key, input.properties.correlation_id

---

Kafka

Property	Value
Connector type	queue (with driver = "kafka")
operation format	Topic name — e.g., "orders", "user-events"

input.* variables

Variable	Source	Description
input.body	Payload	Parsed JSON (or raw string)
input.headers	Kafka	Kafka headers as map
input.topic	Kafka	Topic name
input.partition	Kafka	Partition number
input.offset	Kafka	Message offset
input.key	Kafka	Message key (string)
input.timestamp	Kafka	Unix timestamp

from {
  connector = "kafka"
  operation = "order-events"
}

# Available: input.body.event_type, input.key, input.partition, input.offset

---

Redis Pub/Sub

Property	Value
Connector type	queue (with driver = "redis")
operation format	Channel name or glob pattern — e.g., "orders", "user.*", "*"

Exact channel match first, then pattern match (from PSubscribe), then wildcard "*".

input.* variables

Variable	Source	Description
input._channel	Redis	Channel the message was published to
input._pattern	Redis	Pattern (if matched via PSubscribe), omitted for exact subscriptions
input.<field>	Payload	JSON payload fields merged directly
input.raw	Payload	Raw string payload (if not valid JSON)

from {
  connector = "redis_events"
  operation = "orders.*"
}

# Available: input._channel ("orders.created"), input._pattern ("orders.*"), input.order_id

---

MQTT

Property	Value
Connector type	mqtt
operation format	MQTT topic pattern — e.g., "sensors/+/temperature", "home/#"

Supports MQTT wildcards: + matches single level, # matches multi-level.

input.* variables

Variable	Source	Description
input._topic	MQTT	Topic the message was received on
input._message_id	MQTT	MQTT message ID
input._qos	MQTT	QoS level (0, 1, or 2)
input._retained	MQTT	Whether the message was retained
input.<field>	Payload	JSON payload fields merged directly
input._raw	Payload	Raw string payload (if not valid JSON)

from {
  connector = "mqtt_broker"
  operation = "sensors/+/temperature"
}

# Available: input._topic ("sensors/room1/temperature"), input._qos, input.value, input.unit

---

WebSocket

Property	Value
Connector type	websocket
operation format	Event type: "connect", "disconnect", "message", or custom type string

input.* variables

Event	Variables
"connect"	input.event, input.remote_addr
"disconnect"	input.event
"message"	input.event, data fields merged into input, input.user_id
custom type	input.event, input.data, input.room

from {
  connector = "ws"
  operation = "message"
}

# Available: input.event ("message"), input.user_id, input.text (from message data)

---

SSE (Server-Sent Events)

Property	Value
Connector type	sse
operation format	"connect" or "disconnect"

SSE is unidirectional (server-to-client push). The from block only fires on lifecycle events.

input.* variables

Event	Variables
"connect"	input.event, input.client_id, input.remote_addr
"disconnect"	input.event, input.client_id

from {
  connector = "sse"
  operation = "connect"
}

# Available: input.event, input.client_id, input.remote_addr

---

CDC (Change Data Capture)

Property	Value
Connector type	cdc
operation format	"TRIGGER:table" — e.g., "INSERT:users", "UPDATE:orders", "*:*"

Trigger is uppercase (INSERT, UPDATE, DELETE). Wildcards: "*:users" (any trigger), "INSERT:*" (any table), "*:*" or "*" (all).

input.* variables

Variable	Source	Description
input.trigger	CDC	"INSERT", "UPDATE", or "DELETE"
input.table	CDC	Table name (lowercase)
input.schema	CDC	Schema name (e.g., "public")
input.timestamp	CDC	RFC3339 timestamp
input.new	CDC	New row data (INSERT/UPDATE)
input.old	CDC	Old row data (UPDATE/DELETE)

from {
  connector = "cdc"
  operation = "INSERT:users"
}

# Available: input.trigger, input.table, input.new.email, input.new.id

---

File Watch

Property	Value
Connector type	file (with watch = true)
operation format	Glob pattern — e.g., "*.csv", "reports/*.json", "**/*.csv"

Matches against filename, relative path, or **/ prefix with filename suffix.

input.* variables

Variable	Source	Description
input._path	File	Relative path from base_path
input._name	File	Filename only
input._size	File	File size in bytes
input._mod_time	File	RFC3339 modification time
input._event	File	"created" or "modified"
input._error	File	Error string (if file could not be read)
input.<field>	Content	Single-row file fields merged directly
input.rows	Content	Multi-row file content as array of maps

from {
  connector = "data_files"
  operation = "*.csv"
}

# Available: input._path, input._name, input._event, input.rows (array of CSV rows)

---

Summary

Connector	operation format	Key input.* fields
REST	"METHOD /path" (e.g., "GET /users/:id")	path params, query params, body fields, headers
GraphQL	"Query.field" / "Mutation.field" / "Subscription.field"	argument fields
gRPC	"Service/Method"	proto message fields
SOAP	"OperationName"	SOAP body element children
TCP	message type/pattern string	msg.Data fields
RabbitMQ	routing key (* / # wildcards)	body, headers, properties, routing_key, exchange
Kafka	topic name	body, headers, topic, partition, offset, key, timestamp
Redis Pub/Sub	channel name or glob pattern	_channel, _pattern, payload fields
MQTT	topic pattern (+ / # wildcards)	_topic, _message_id, _qos, _retained, payload fields
WebSocket	"connect" / "disconnect" / "message" / custom type	event, data fields, user_id, room
SSE	"connect" / "disconnect"	event, client_id, remote_addr
CDC	"TRIGGER:table" (e.g., "INSERT:users")	trigger, table, schema, new, old, timestamp
File watch	glob pattern (e.g., "*.csv")	_path, _name, _size, _mod_time, _event, content fields

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See also: Flows for from block syntax, Destination Properties for to block properties, Configuration Reference for all HCL blocks.