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Azure Cache for Redis output binding for Azure Functions (preview)

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The Azure Cache for Redis output bindings lets you change the keys in a cache based on a set of available trigger on the cache.

For information on setup and configuration details, see the overview.

Important

The Node.js v4 model for Functions isn't yet supported by the Azure Cache for Redis extension. For more details about how the v4 model works, refer to the Azure Functions Node.js developer guide. To learn more about the differences between v3 and v4, refer to the migration guide.

Important

The Python v2 model for Functions isn't yet supported by the Azure Cache for Redis extension. For more details about how the v2 model works, refer to the Azure Functions Python developer guide.

Example

A C# function can be created by using one of the following C# modes:

  • Isolated worker model: Compiled C# function that runs in a worker process that's isolated from the runtime. Isolated worker process is required to support C# functions running on LTS and non-LTS versions .NET and the .NET Framework. Extensions for isolated worker process functions use Microsoft.Azure.Functions.Worker.Extensions.* namespaces.
  • In-process model: Compiled C# function that runs in the same process as the Functions runtime. In a variation of this model, Functions can be run using C# scripting, which is supported primarily for C# portal editing. Extensions for in-process functions use Microsoft.Azure.WebJobs.Extensions.* namespaces.

The following example shows a pub/sub trigger on the set event with an output binding to the same Redis instance. The set event triggers the cache and the output binding returns a delete command for the key that triggered the function.

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.

using Microsoft.Extensions.Logging;

namespace Microsoft.Azure.WebJobs.Extensions.Redis.Samples.RedisOutputBinding
{
    internal class SetDeleter
    {
        [FunctionName(nameof(SetDeleter))]
        public static void Run(
            [RedisPubSubTrigger(Common.connectionStringSetting, "__keyevent@0__:set")] string key,
            [Redis(Common.connectionStringSetting, "DEL")] out string[] arguments,
            ILogger logger)
        {
            logger.LogInformation($"Deleting recently SET key '{key}'");
            arguments = new string[] { key };
        }
    }
}

The following example shows a pub/sub trigger on the set event with an output binding to the same Redis instance. The set event triggers the cache and the output binding returns a delete command for the key that triggered the function.

package com.function.RedisOutputBinding;

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

public class SetDeleter {
    @FunctionName("SetDeleter")
    @RedisOutput(
                name = "value",
                connection = "redisConnectionString",
                command = "DEL")
    public String run(
            @RedisPubSubTrigger(
                name = "key",
                connection = "redisConnectionString",
                channel = "__keyevent@0__:set")
                String key,
            final ExecutionContext context) {
        context.getLogger().info("Deleting recently SET key '" + key + "'");
        return key;
    }
}

This example shows a pub/sub trigger on the set event with an output binding to the same Redis instance. The set event triggers the cache and the output binding returns a delete command for the key that triggered the function.

The bindings are defined in this `function.json`` file:

{
    "bindings": [
        {
            "type": "redisPubSubTrigger",
            "connection": "redisConnectionString",
            "channel": "__keyevent@0__:set",
            "name": "key",
            "direction": "in"
        },
        {
            "type": "redis",
            "connection": "redisConnectionString",
            "command": "DEL",
            "name": "$return",
            "direction": "out"
        }
    ],
    "scriptFile": "index.js"
}

This code from the index.js file takes the key from the trigger and returns it to the output binding to delete the cached item.

module.exports = async function (context, key) {
    context.log("Deleting recently SET key '" + key + "'");
    return key;
}

This example shows a pub/sub trigger on the set event with an output binding to the same Redis instance. The set event triggers the cache and the output binding returns a delete command for the key that triggered the function.

The bindings are defined in this function.json file:

{
    "bindings": [
        {
            "type": "redisPubSubTrigger",
            "connection": "redisLocalhost",
            "channel": "__keyevent@0__:set",
            "name": "key",
            "direction": "in"
        },
        {
            "type": "redis",
            "connection": "redisLocalhost",
            "command": "DEL",
            "name": "retVal",
            "direction": "out"
        }
    ],
    "scriptFile": "run.ps1"
}

This code from the run.ps1 file takes the key from the trigger and passes it to the output binding to delete the cached item.

param($key, $TriggerMetadata)
Write-Host "Deleting recently SET key '$key'"
Push-OutputBinding -Name retVal -Value $key

This example shows a pub/sub trigger on the set event with an output binding to the same Redis instance. The set event triggers the cache and the output binding returns a delete command for the key that triggered the function.

The bindings are defined in this function.json file:

{
    "bindings": [
        {
            "type": "redisPubSubTrigger",
            "connection": "redisLocalhost",
            "channel": "__keyevent@0__:set",
            "name": "key",
            "direction": "in"
        },
        {
            "type": "redis",
            "connection": "redisLocalhost",
            "command": "DEL",
            "name": "$return",
            "direction": "out"
        }
    ],
    "scriptFile": "__init__.py"
}

This code from the __init__.py file takes the key from the trigger and passes it to the output binding to delete the cached item.

import logging

def main(key: str) -> str:
    logging.info("Deleting recently SET key '" + key + "'")
    return key

Attributes

Note

All commands are supported for this binding.

The way in which you define an output binding parameter depends on whether your C# functions runs in-process or in an isolated worker process.

The output binding is defined this way:

Definition Example Description
On an out parameter [Redis(<Connection>, <Command>)] out string <Return_Variable> The string variable returned by the method is a key value that the binding uses to execute the command against the specific cache.

In this case, the type returned by the method is a key value that the binding uses to execute the command against the specific cache.

When your function has multiple output bindings, you can instead apply the binding attribute to the property of a type that is a key value, which the binding uses to execute the command against the specific cache. For more information, see Multiple output bindings.

Regardless of the C# process mode, the same properties are supported by the output binding attribute:

Attribute property Description
Connection The name of the application setting that contains the cache connection string, such as: <cacheName>.redis.cache.windows.net:6380,password...
Command The redis-cli command to be executed on the cache, such as: DEL.

Annotations

The RedisOutput annotation supports these properties:

Property Description
name The name of the specific input binding.
connection The name of the application setting that contains the cache connection string, such as: <cacheName>.redis.cache.windows.net:6380,password...
command The redis-cli command to be executed on the cache, such as: DEL.

Configuration

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

Property Description
name The name of the specific input binding.
connection The name of the application setting that contains the cache connection string, such as: <cacheName>.redis.cache.windows.net:6380,password...
command The redis-cli command to be executed on the cache, such as: DEL.

See the Example section for complete examples.

Usage

The output returns a string, which is the key of the cache entry on which apply the specific command.

There are three types of connections that are allowed from an Azure Functions instance to a Redis Cache in your deployments. For local development, you can also use service principal secrets. Use the appsettings to configure each of the following types of client authentication, assuming the Connection was set to Redis in the function.

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