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RedisListTrigger Azure Function (preview)

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The RedisListTrigger pops new elements from a list and surfaces those entries to the function.

Scope of availability for functions triggers

Tier Basic Standard, Premium Enterprise, Enterprise Flash
Lists Yes Yes Yes

Important

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

Example

The following sample polls the key listTest at a localhost Redis instance at 127.0.0.1:6379:

The isolated process examples aren't available in preview.

The following sample polls the key listTest at a localhost Redis instance at redisLocalhost:

    @FunctionName("ListTrigger")
    public void ListTrigger(
            @RedisListTrigger(
                name = "entry",
                connectionStringSetting = "redisLocalhost",
                key = "listTest",
                pollingIntervalInMs = 100,
                messagesPerWorker = 10,
                count = 1,
                listPopFromBeginning = false)
                String entry,
            final ExecutionContext context) {
            context.getLogger().info(entry);
    }

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": "redisListTrigger",
      "listPopFromBeginning": true,
      "connectionStringSetting": "redisLocalhost",
      "key": "listTest",
      "pollingIntervalInMs": 1000,
      "messagesPerWorker": 100,
      "count": 10,
      "name": "entry",
      "direction": "in"
    }
  ],
  "scriptFile": "index.js"
}

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

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

{
  "bindings": [
    {
      "type": "redisListTrigger",
      "listPopFromBeginning": true,
      "connectionStringSetting": "redisLocalhost",
      "key": "listTest",
      "pollingIntervalInMs": 1000,
      "messagesPerWorker": 100,
      "count": 10,
      "name": "entry",
      "direction": "in"
    }
  ],
  "scriptFile": "run.ps1"
}

This sample uses the same __init__.py file, with binding data in the function.json file.

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.

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": "redisListTrigger",
      "listPopFromBeginning": true,
      "connectionStringSetting": "redisLocalhost",
      "key": "listTest",
      "pollingIntervalInMs": 1000,
      "messagesPerWorker": 100,
      "count": 10,
      "name": "entry",
      "direction": "in"
    }
  ],
  "scriptFile": "__init__.py"
}

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
Key Key to read from. This field can be resolved using INameResolver. Yes
PollingIntervalInMs How often to poll Redis in milliseconds. Optional 1000
MessagesPerWorker How many messages each functions instance should process. Used to determine how many instances the function should scale to. Optional 100
Count Number of entries to pop from Redis at one time. These are processed in parallel. Only supported on Redis 6.2+ using the COUNT argument in LPOP and RPOP. Optional 10
ListPopFromBeginning Determines whether to pop entries from the beginning using LPOP, or to pop entries from the end using RPOP. Optional true

Annotations

Parameter Description Required Default
name "entry"
connectionStringSetting The name of the setting in the appsettings that contains the cache connection string. For example: <cacheName>.redis.cache.windows.net:6380,password... Yes
key This field can be resolved using INameResolver. Yes
pollingIntervalInMs How often to poll Redis in milliseconds. Optional 1000
messagesPerWorker How many messages each functions instance should process. Used to determine how many instances the function should scale to. Optional 100
count Number of entries to read from Redis at one time. These are processed in parallel. Optional 10
listPopFromBeginning Whether to delete the stream entries after the function has run. Yes true

Configuration

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

function.json Property Description Optional Default
type Name of the trigger. No
listPopFromBeginning Whether to delete the stream entries after the function has run. Set to true. Yes true
connectionString The name of the setting in the appsettings that contains the cache connection string. For example: <cacheName>.redis.cache.windows.net:6380,password... No
key This field can be resolved using INameResolver. No
pollingIntervalInMs How often to poll Redis in milliseconds. Yes 1000
messagesPerWorker How many messages each functions instance should process. Used to determine how many instances the function should scale to. Yes 100
count Number of entries to read from the cache at one time. These are processed in parallel. Yes 10
name ? Yes
direction Set to in. No

See the Example section for complete examples.

Usage

The RedisListTrigger pops new elements from a list and surfaces those entries to the function. The trigger polls Redis at a configurable fixed interval, and uses LPOP and RPOP to pop entries from the lists.

Output

Note

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

StackExchange.Redis.RedisValue

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

Note

Once the RedisListTrigger 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.

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