Channel Commands

Channel commands are used to send messages to Redis Pub/Sub channels. To receive messages, see Sources (Listeners).

This page covers: PUBLISH

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PUBLISH

Publish a message to a Redis Pub/Sub channel.

📘 Redis Reference: PUBLISH

XML Example

<lettuce-redis:publish doc:name="Publish notification"
    config-ref="Redis_Config"
    channel="order-events"
    message='{"orderId": "12345", "status": "shipped"}'/>

Parameters

Parameter	Type	Required	Default	Description
channel	String	Yes	—	The name of the channel to publish to
message	String	Yes	—	The message content to publish

Output

Type: Long

The number of subscribers that received the message. A return value of 0 means no clients were subscribed to the channel when the message was published.

Message Delivery

Redis Pub/Sub is fire-and-forget. If no subscriber is listening when PUBLISH is called, the message is lost. For durable messaging, consider using Redis Streams instead.

Errors

Error Type	Condition
REDIS:COMMAND	Connection failure or server error

Usage

Configuration

PUBLISH uses the standard configuration (lettuce-redis:config), not the pub/sub configuration. Only the SUBSCRIBE and PSUBSCRIBE sources require the pub/sub configuration.

Common pattern: Publish and subscribe in the same application

<!-- Standard config for PUBLISH -->
<lettuce-redis:config name="Redis_Config">
    <lettuce-redis:connection
        host="${redis.host}"
        port="${redis.port}"
        tls="false"
        password="${secure::redis.password}"/>
</lettuce-redis:config>

<!-- Pub/Sub config for SUBSCRIBE sources -->
<lettuce-redis:pubsub-config name="Redis_PubSub_Config">
    <lettuce-redis:pubsub-connection
        host="${redis.host}"
        port="${redis.port}"
        tls="false"
        password="${secure::redis.password}"/>
</lettuce-redis:pubsub-config>

<!-- Publish messages when orders are placed -->
<flow name="order-publisher">
    <http:listener config-ref="HTTP_Config" path="/orders"/>

    <lettuce-redis:publish
        config-ref="Redis_Config"
        channel="order-events"
        message="#[payload]"/>

    <set-variable variableName="subscriberCount" value="#[payload]"/>

    <logger level="INFO"
        message="Published to #[vars.subscriberCount] subscribers"/>
</flow>

<!-- Subscribe to order events and process them -->
<flow name="order-subscriber">
    <lettuce-redis:subscribe-channel
        config-ref="Redis_PubSub_Config"
        channels="#[['order-events']]"/>

    <logger level="INFO"
        message="Received order event: #[payload]"/>

    <flow-ref name="process-order-event"/>
</flow>

See Also

• Sources (Listeners) — SUBSCRIBE and PSUBSCRIBE for receiving messages
• Redis Streams — Durable, persistent messaging with consumer groups