title	description	author	zone_pivot_groups	ms.author	ms.service	ms.custom	ms.topic	ms.date
Using RedisPubSubTrigger Azure Function (preview)	Learn how to use RedisPubSubTrigger Azure Function	flang-msft	programming-languages-set-functions-lang-workers	franlanglois	azure-functions	devx-track-dotnet, devx-track-extended-java, devx-track-js, devx-track-python	reference	08/07/2023

RedisPubSubTrigger Azure Function (preview)

Redis features publish/subscribe functionality that enables messages to be sent to Redis and broadcast to subscribers.

Scope of availability for functions triggers

Tier	Basic	Standard, Premium	Enterprise, Enterprise Flash
Pub/Sub Trigger	Yes	Yes	Yes

Warning

This trigger isn't supported on a consumption plan because Redis PubSub requires clients to always be actively listening to receive all messages. For consumption plans, your function might miss certain messages published to the channel.

Examples

::: zone pivot="programming-language-csharp"

[!INCLUDE dotnet-execution]

In-process

This sample listens to the channel pubsubTest.

[FunctionName(nameof(PubSubTrigger))]
public static void PubSubTrigger(
    [RedisPubSubTrigger("redisConnectionString", "pubsubTest")] string message,
    ILogger logger)
{
    logger.LogInformation(message);
}

This sample listens to any keyspace notifications for the key myKey.

[FunctionName(nameof(KeyspaceTrigger))]
public static void KeyspaceTrigger(
    [RedisPubSubTrigger("redisConnectionString", "__keyspace@0__:myKey")] string message,
    ILogger logger)
{
    logger.LogInformation(message);
}

This sample listens to any keyevent notifications for the delete command DEL.

[FunctionName(nameof(KeyeventTrigger))]
public static void KeyeventTrigger(
    [RedisPubSubTrigger("redisConnectionString", "__keyevent@0__:del")] string message,
    ILogger logger)
{
    logger.LogInformation(message);
}

Isolated process

The isolated process examples aren't available in preview.

//TBD

::: zone-end ::: zone pivot="programming-language-java"

This sample listens to the channel pubsubTest.

@FunctionName("PubSubTrigger")
    public void PubSubTrigger(
            @RedisPubSubTrigger(
                name = "message",
                connectionStringSetting = "redisConnectionString",
                channel = "pubsubTest")
                String message,
            final ExecutionContext context) {
            context.getLogger().info(message);
    }

This sample listens to any keyspace notifications for the key myKey.

@FunctionName("KeyspaceTrigger")
    public void KeyspaceTrigger(
            @RedisPubSubTrigger(
                name = "message",
                connectionStringSetting = "redisConnectionString",
                channel = "__keyspace@0__:myKey")
                String message,
            final ExecutionContext context) {
            context.getLogger().info(message);
    }

This sample listens to any keyevent notifications for the delete command DEL.

 @FunctionName("KeyeventTrigger")
    public void KeyeventTrigger(
            @RedisPubSubTrigger(
                name = "message",
                connectionStringSetting = "redisConnectionString",
                channel = "__keyevent@0__:del")
                String message,
            final ExecutionContext context) {
            context.getLogger().info(message);
    }

::: zone-end ::: zone pivot="programming-language-javascript"

v3

This sample uses the same index.js file, with binding data in the function.json file determining on which channel the trigger occurs.

Here's the index.js file:

module.exports = async function (context, message) {
    context.log(message);
}

From function.json:

Here's binding data to listen to the channel pubsubTest.

{
  "bindings": [
    {
      "type": "redisPubSubTrigger",
      "connectionStringSetting": "redisConnectionString",
      "channel": "pubsubTest",
      "name": "message",
      "direction": "in"
    }
  ],
  "scriptFile": "index.js"
}

Here's binding data to listen to keyspace notifications for the key myKey.

{
  "bindings": [
    {
      "type": "redisPubSubTrigger",
      "connectionStringSetting": "redisConnectionString",
       "channel": "__keyspace@0__:myKey",
      "name": "message",
      "direction": "in"
    }
  ],
  "scriptFile": "index.js"
}

Here's binding data to listen to keyevent notifications for the delete command DEL.

{
  "bindings": [
    {
      "type": "redisPubSubTrigger",
      "connectionStringSetting": "redisConnectionString",
      "channel": "__keyevent@0__:del",
      "name": "message",
      "direction": "in"
    }
  ],
  "scriptFile": "index.js"
}

v4

The JavaScript v4 programming model example isn't available in preview.

::: zone-end ::: zone pivot="programming-language-powershell"

This sample uses the same run.ps1 file, with binding data in the function.json file determining on which channel the trigger occurs.

Here's the run.ps1 file:

param($message, $TriggerMetadata)
Write-Host $message

From function.json:

Here's binding data to listen to the channel pubsubTest.

{
  "bindings": [
    {
      "type": "redisPubSubTrigger",
      "connectionStringSetting": "redisConnectionString",
      "channel": "pubsubTest",
      "name": "message",
      "direction": "in"
    }
  ],
  "scriptFile": "run.ps1"
}

Here's binding data to listen to keyspace notifications for the key myKey.

{
  "bindings": [
    {
      "type": "redisPubSubTrigger",
      "connectionStringSetting": "redisConnectionString",
       "channel": "__keyspace@0__:myKey",
      "name": "message",
      "direction": "in"
    }
  ],
  "scriptFile": "run.ps1"
}

Here's binding data to listen to keyevent notifications for the delete command DEL.

{
  "bindings": [
    {
      "type": "redisPubSubTrigger",
      "connectionStringSetting": "redisConnectionString",
      "channel": "__keyevent@0__:del",
      "name": "message",
      "direction": "in"
    }
  ],
  "scriptFile": "run.ps1"
}

::: zone-end ::: zone pivot="programming-language-python"

v1

The Python v1 programming model requires you to define bindings in a separate function.json file in the function folder. For more information, see the Python developer guide.

This sample uses the same __init__.py file, with binding data in the function.json file determining on which channel the trigger occurs.

Here's the __init__.py file:

import logging

def main(message: str):
    logging.info(message)

From function.json:

Here's binding data to listen to the channel pubsubTest.

{
  "bindings": [
    {
      "type": "redisPubSubTrigger",
      "connectionStringSetting": "redisConnectionString",
      "channel": "pubsubTest",
      "name": "message",
      "direction": "in"
    }
  ],
  "scriptFile": "__init__.py"
}

Here's binding data to listen to keyspace notifications for the key myKey.

{
  "bindings": [
    {
      "type": "redisPubSubTrigger",
      "connectionStringSetting": "redisConnectionString",
      "channel": "__keyspace@0__:myKey",
      "name": "message",
      "direction": "in"
    }
  ],
  "scriptFile": "__init__.py"
}

Here's binding data to listen to keyevent notifications for the delete command DEL.

{
  "bindings": [
    {
      "type": "redisPubSubTrigger",
      "connectionStringSetting": "redisConnectionString",
      "channel": "__keyevent@0__:del",
      "name": "message",
      "direction": "in"
    }
  ],
  "scriptFile": "__init__.py"
}

v2

The Python v2 programming model example isn't available in preview.

::: zone-end ::: zone pivot="programming-language-csharp"

Attributes

Parameter	Description	Required	Default
`ConnectionStringSetting`	Name of the setting in the `appsettings` that holds the cache connection string. For example,`<cacheName>.redis.cache.windows.net:6380,password=...`.	Yes
`Channel`	The pub sub channel that the trigger should listen to. Supports glob-style channel patterns. This field can be resolved using `INameResolver`.	Yes

::: zone-end ::: zone pivot="programming-language-java"

Annotations

| Parameter | Description | Required | Default | |---------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------|: -----:| -----:| | name | Name of the variable holding the value returned by the function. | Yes | | | connectionStringSetting | Name of the setting in the appsettings that holds the cache connection string (for example, <cacheName>.redis.cache.windows.net:6380,password=...) | Yes | | | channel | The pub sub channel that the trigger should listen to. Supports glob-style channel patterns. | Yes | |

::: zone-end ::: zone pivot="programming-language-javascript,programming-language-powershell,programming-language-python"

Configuration

function.json property	Description	Required
`type`	Trigger type. For the pub sub trigger, this is `redisPubSubTrigger`.	Yes
`connectionStringSetting`	Name of the setting in the `appsettings` that holds the cache connection string (for example, `<cacheName>.redis.cache.windows.net:6380,password=...`)	Yes
`channel`	Name of the pub sub channel that is being subscribed to	Yes
`name`	Name of the variable holding the value returned by the function.	Yes
`direction`	Must be set to `in`.	Yes

::: zone-end

Important

The connectionStringSetting parameter does not hold the Redis cache connection string itself. Instead, it points to the name of the environment variable that holds the connection string. This makes the application more secure. For more information, see Redis connection string.

Usage

Redis features publish/subscribe functionality that enables messages to be sent to Redis and broadcast to subscribers. The RedisPubSubTrigger enables Azure Functions to be triggered on pub/sub activity. The RedisPubSubTriggersubscribes to a specific channel pattern using PSUBSCRIBE, and surfaces messages received on those channels to the function.

Prerequisites and limitations

The RedisPubSubTrigger isn't capable of listening to keyspace notifications on clustered caches.
Basic tier functions don't support triggering on keyspace or keyevent notifications through the RedisPubSubTrigger.
The RedisPubSubTrigger isn't supported on a consumption plan because Redis PubSub requires clients to always be actively listening to receive all messages. For consumption plans, your function might miss certain messages published to the channel.
Functions with the RedisPubSubTrigger shouldn't be scaled out to multiple instances. Each instance listens and processes each pub sub message, resulting in duplicate processing

Warning

This trigger isn't supported on a consumption plan because Redis PubSub requires clients to always be actively listening to receive all messages. For consumption plans, your function might miss certain messages published to the channel.

Triggering on keyspace notifications

Redis offers a built-in concept called keyspace notifications. When enabled, this feature publishes notifications of a wide range of cache actions to a dedicated pub/sub channel. Supported actions include actions that affect specific keys, called keyspace notifications, and specific commands, called keyevent notifications. A huge range of Redis actions are supported, such as SET, DEL, and EXPIRE. The full list can be found in the keyspace notification documentation.

The keyspace and keyevent notifications are published with the following syntax:

PUBLISH __keyspace@0__:<affectedKey> <command>
PUBLISH __keyevent@0__:<affectedCommand> <key>

Because these events are published on pub/sub channels, the RedisPubSubTrigger is able to pick them up. See the RedisPubSubTrigger section for more examples.

Important

In Azure Cache for Redis, keyspace events must be enabled before notifications are published. For more information, see Advanced Settings.

Output

::: zone pivot="programming-language-csharp"

Note

Once the RedisPubSubTrigger becomes generally available, the following information will be moved to a dedicated Output page.

Output Type	Description
`StackExchange.Redis.ChannelMessage`	The value returned by `StackExchange.Redis`.
`StackExchange.Redis.RedisValue`	`string`, `byte[]`, `ReadOnlyMemory<byte>`: The message from the channel.
`Custom`	The trigger uses Json.NET serialization to map the message from the channel from a `string` into a custom type.

::: zone-end

::: zone pivot="programming-language-java,programming-language-javascript,programming-language-powershell,programming-language-python"

Note

Once the RedisPubSubTrigger becomes generally available, the following information will be moved to a dedicated Output page.

Output Type	Description
`byte[]`	The message from the channel.
`string`	The message from the channel.
`Custom`	The trigger uses Json.NET serialization to map the message from the channel from a `string` into a custom type.

::: zone-end ::: zone pivot="programming-language-java"

::: zone-end ::: zone pivot="programming-language-javascript,programming-language-powershell"

::: zone-end ::: zone pivot="programming-language-powershell"

::: zone-end ::: zone pivot="programming-language-python"

::: zone-end

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functions-bindings-cache-trigger-redispubsub.md

functions-bindings-cache-trigger-redispubsub.md

RedisPubSubTrigger Azure Function (preview)

Scope of availability for functions triggers

Examples

In-process

Isolated process

v3

v4

v1

v2

Attributes

Annotations

Configuration

Usage

Prerequisites and limitations

Triggering on keyspace notifications

Output

Related content

Files

functions-bindings-cache-trigger-redispubsub.md

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File metadata and controls

RedisPubSubTrigger Azure Function (preview)

Scope of availability for functions triggers

Examples

In-process

Isolated process

v3

v4

v1

v2

Attributes

Annotations

Configuration

Usage

Prerequisites and limitations

Triggering on keyspace notifications

Output

Related content