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title description author zone_pivot_groups ms.author ms.service ms.custom ms.topic ms.date
RedisStreamTrigger for Azure Functions
Learn how to use RedisStreamTrigger Azure Function for Azure Cache for Redis.
flang-msft
programming-languages-set-functions-lang-workers
franlanglois
azure-functions
devx-track-dotnet, devx-track-extended-java, devx-track-js, devx-track-python, ignite-2024
reference
07/12/2024

RedisStreamTrigger for Azure Functions

The RedisStreamTrigger reads new entries from a stream and surfaces those elements to the function.

Scope of availability for functions triggers

Trigger Type Azure Managed Redis Azure Cache for Redis
Streams Yes Yes

Important

When using Azure Managed Redis or the Enterprise tiers of Azure Cache for Redis, use port 10000 rather than port 6380 or 6379.

Important

Redis triggers aren't currently supported for functions running in the Consumption plan.

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

[!INCLUDE functions-nodejs-model-tabs-redis-preview]
::: zone-end
::: zone pivot="programming-language-python"

[!INCLUDE functions-python-model-tabs-redis-preview] ::: zone-end

Example

Important

For .NET functions, using the isolated worker model is recommended over the in-process model. For a comparison of the in-process and isolated worker models, see differences between the isolated worker model and the in-process model for .NET on Azure Functions.

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

[!INCLUDE dotnet-execution]

Isolated worker model

using Microsoft.Extensions.Logging;

namespace Microsoft.Azure.Functions.Worker.Extensions.Redis.Samples.RedisStreamTrigger
{
    internal class SimpleStreamTrigger
    {
        private readonly ILogger<SimpleStreamTrigger> logger;

        public SimpleStreamTrigger(ILogger<SimpleStreamTrigger> logger)
        {
            this.logger = logger;
        }

        [Function(nameof(SimpleStreamTrigger))]
        public void Run(
            [RedisStreamTrigger(Common.connectionStringSetting, "streamKey")] string entry)
        {
            logger.LogInformation(entry);
        }
    }
}

In-process model

[!INCLUDE functions-in-process-model-retirement-note]

using Microsoft.Extensions.Logging;

namespace Microsoft.Azure.WebJobs.Extensions.Redis.Samples.RedisStreamTrigger
{
    internal class SimpleStreamTrigger
    {
        [FunctionName(nameof(SimpleStreamTrigger))]
        public static void Run(
            [RedisStreamTrigger(Common.connectionStringSetting, "streamKey")] string entry,
            ILogger logger)
        {
            logger.LogInformation(entry);
        }
    }
}

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

package com.function.RedisStreamTrigger;

import com.microsoft.azure.functions.*;
import com.microsoft.azure.functions.annotation.*;
import com.microsoft.azure.functions.redis.annotation.*;

public class SimpleStreamTrigger {
    @FunctionName("SimpleStreamTrigger")
    public void run(
            @RedisStreamTrigger(
                name = "req",
                connection = "redisConnectionString",
                key = "streamTest",
                pollingIntervalInMs = 1000,
                maxBatchSize = 1)
                String message,
            final ExecutionContext context) {
            context.getLogger().info(message);
    }
}

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

Model v3

This sample uses the same index.js file, with binding data in the function.json file.

Here's the index.js file:

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

From function.json, here's the binding data:

{
  "bindings": [
    {
      "type": "redisStreamTrigger",
      "connection": "redisConnectionString",
      "key": "streamTest",
      "pollingIntervalInMs": 1000,
      "maxBatchSize": 16,
      "name": "entry",
      "direction": "in"
    }
  ],
  "scriptFile": "index.js"
}

Model v4

[!INCLUDE functions-nodejs-model-tabs-redis-preview]

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

This sample uses the same run.ps1 file, with binding data in the function.json file.

Here's the run.ps1 file:

param($entry, $TriggerMetadata)
Write-Host ($entry | ConvertTo-Json)

From function.json, here's the binding data:

{
  "bindings": [
    {
      "type": "redisStreamTrigger",
      "connection": "redisConnectionString",
      "key": "streamTest",
      "pollingIntervalInMs": 1000,
      "maxBatchSize": 16,
      "name": "entry",
      "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.

Here's the __init__.py file:

import logging

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

From function.json, here's the binding data:

{
  "bindings": [
    {
      "type": "redisStreamTrigger",
      "connection": "redisConnectionString",
      "key": "streamTest",
      "pollingIntervalInMs": 1000,
      "maxBatchSize": 16,
      "name": "entry",
      "direction": "in"
    }
  ],
  "scriptFile": "__init__.py"
}

v2

[!INCLUDE functions-python-model-tabs-redis-preview]

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

Attributes

Parameters Description Required Default
Connection The name of the application setting that contains the cache connection string, such as: <cacheName>.redis.cache.windows.net:6380,password... Yes
Key Key to read from. Yes
PollingIntervalInMs How often to poll the Redis server in milliseconds. Optional 1000
MessagesPerWorker The number of messages each functions worker should process. Used to determine how many workers the function should scale to. Optional 100
Count Number of elements to pull from Redis at one time. Optional 10
DeleteAfterProcess Indicates if the function deletes the stream entries after processing. Optional false

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

Annotations

Parameter Description Required Default
name entry Yes
connection The name of the application setting that contains the cache connection string, such as: <cacheName>.redis.cache.windows.net:6380,password... Yes
key Key to read from. Yes
pollingIntervalInMs How frequently to poll Redis, in milliseconds. Optional 1000
messagesPerWorker The number of messages each functions worker should process. It's used to determine how many workers the function should scale to. Optional 100
count Number of entries to read from Redis at one time. Entries are processed in parallel. Optional 10
deleteAfterProcess Whether to delete the stream entries after the function has run. Optional false

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

Configuration

The following table explains the binding configuration properties that you set in the function.json file.

function.json Properties Description Required Default
type Yes
deleteAfterProcess Optional false
connection The name of the application setting that contains the cache connection string, such as: <cacheName>.redis.cache.windows.net:6380,password... Yes
key The key to read from. Yes
pollingIntervalInMs How often to poll Redis in milliseconds. Optional 1000
messagesPerWorker (optional) The number of messages each functions worker should process. Used to determine how many workers the function should scale Optional 100
count Number of entries to read from Redis at one time. These are processed in parallel. Optional 10
name Yes
direction Yes

::: zone-end

See the Example section for complete examples.

Usage

The RedisStreamTrigger Azure Function reads new entries from a stream and surfaces those entries to the function.

The trigger polls Redis at a configurable fixed interval, and uses XREADGROUP to read elements from the stream.

The consumer group for all instances of a function is the name of the function, that is, SimpleStreamTrigger for the StreamTrigger sample.

Each functions instance uses the WEBSITE_INSTANCE_ID or generates a random GUID to use as its consumer name within the group to ensure that scaled out instances of the function don't read the same messages from the stream.

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

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

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