Azure Cosmos DB trigger for Azure Functions 2.x and higher

The Python v2 programming model lets you define bindings using decorators directly in your Python function code. For more information, see the Python developer guide.

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.

An isolated worker process class library compiled C# function runs in a process isolated from the runtime.

An in-process class library is a compiled C# function runs in the same process as the Functions runtime.

Apps using Azure Cosmos DB extension version 4.x or higher have different attribute properties, which are shown here. This example refers to a simple ToDoItem type.

namespace CosmosDBSamplesV2
{
    // Customize the model with your own desired properties
    public class ToDoItem
    {
        public string id { get; set; }
        public string Description { get; set; }
    }
}

using System.Collections.Generic;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Host;
using Microsoft.Extensions.Logging;

namespace CosmosDBSamplesV2
{
    public static class CosmosTrigger
    {
        [FunctionName("CosmosTrigger")]
        public static void Run([CosmosDBTrigger(
            databaseName: "databaseName",
            containerName: "containerName",
            Connection = "CosmosDBConnectionSetting",
            LeaseContainerName = "leases",
            CreateLeaseContainerIfNotExists = true)]IReadOnlyList<ToDoItem> input, ILogger log)
        {
            if (input != null && input.Count > 0)
            {
                log.LogInformation("Documents modified " + input.Count);
                log.LogInformation("First document Id " + input[0].id);
            }
        }
    }
}

The following example shows a C# function that is invoked when there are inserts or updates in the specified database and collection.

using Microsoft.Azure.Documents;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Host;
using System.Collections.Generic;
using Microsoft.Extensions.Logging;

namespace CosmosDBSamplesV2
{
    public static class CosmosTrigger
    {
        [FunctionName("CosmosTrigger")]
        public static void Run([CosmosDBTrigger(
            databaseName: "ToDoItems",
            collectionName: "Items",
            ConnectionStringSetting = "CosmosDBConnection",
            LeaseCollectionName = "leases",
            CreateLeaseCollectionIfNotExists = true)]IReadOnlyList<Document> documents,
            ILogger log)
        {
            if (documents != null && documents.Count > 0)
            {
                log.LogInformation($"Documents modified: {documents.Count}");
                log.LogInformation($"First document Id: {documents[0].Id}");
            }
        }
    }
}

This example refers to a simple ToDoItem type:

public class ToDoItem
{
    public string? Id { get; set; }
    public string? Description { get; set; }
}

The following function is invoked when there are inserts or updates in the specified database and collection.

[Function("CosmosTrigger")]
public void Run([CosmosDBTrigger(
    databaseName: "ToDoItems",
    containerName:"TriggerItems",
    Connection = "CosmosDBConnection",
    LeaseContainerName = "leases",
    CreateLeaseContainerIfNotExists = true)] IReadOnlyList<ToDoItem> todoItems,
    FunctionContext context)
{
    if (todoItems is not null && todoItems.Any())
    {
        foreach (var doc in todoItems)
        {
            _logger.LogInformation("ToDoItem: {desc}", doc.Description);
        }
    }
}

The following code defines a MyDocument type:

    public class MyDocument
    {
        public string Id { get; set; }

        public string Text { get; set; }

        public int Number { get; set; }

        public bool Boolean { get; set; }
    }

An IReadOnlyList<T> is used as the Azure Cosmos DB trigger binding parameter in the following example:

// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the MIT License. See License.txt in the project root for license information.

using System.Collections.Generic;
using System.Linq;
using Microsoft.Azure.Functions.Worker;
using Microsoft.Extensions.Logging;

namespace SampleApp
{
    public class CosmosDBFunction
    {
        private readonly ILogger<CosmosDBFunction> _logger;

        public CosmosDBFunction(ILogger<CosmosDBFunction> logger)
        {
            _logger = logger;
        }

        //<docsnippet_exponential_backoff_retry_example>
        [Function(nameof(CosmosDBFunction))]
        [ExponentialBackoffRetry(5, "00:00:04", "00:15:00")]
        [CosmosDBOutput("%CosmosDb%", "%CosmosContainerOut%", Connection = "CosmosDBConnection", CreateIfNotExists = true)]
        public object Run(
            [CosmosDBTrigger(
                "%CosmosDb%",
                "%CosmosContainerIn%",
                Connection = "CosmosDBConnection",
                LeaseContainerName = "leases",
                CreateLeaseContainerIfNotExists = true)] IReadOnlyList<MyDocument> input,
            FunctionContext context)
        {
            if (input != null && input.Any())
            {
                foreach (var doc in input)
                {
                    _logger.LogInformation("Doc Id: {id}", doc.Id);
                }

                // Cosmos Output
                return input.Select(p => new { id = p.Id });
            }

            return null;
        }
        //</docsnippet_exponential_backoff_retry_example>
    }

    public class MyDocument
    {
        public string Id { get; set; }

        public string Text { get; set; }

        public int Number { get; set; }

        public bool Boolean { get; set; }
    }
}

This example requires the following using statements:

using System.Collections.Generic;
using System.Linq;
using Microsoft.Azure.Functions.Worker;
using Microsoft.Extensions.Logging;

Because of schema changes in the Azure Cosmos DB SDK, version 4.x of the Azure Cosmos DB extension requires azure-functions-java-library V3.0.0 for Java functions.

    @FunctionName("CosmosDBTriggerFunction")
    public void run(
        @CosmosDBTrigger(
            name = "items",
            databaseName = "ToDoList",
            containerName = "Items",
            leaseContainerName="leases",
            connection = "AzureCosmosDBConnection",
            createLeaseContainerIfNotExists = true
        )
        Object inputItem,
        final ExecutionContext context
    ) {
        context.getLogger().info("Items modified: " + inputItems.size());
    }

    @FunctionName("cosmosDBMonitor")
    public void cosmosDbProcessor(
        @CosmosDBTrigger(name = "items",
            databaseName = "ToDoList",
            collectionName = "Items",
            leaseCollectionName = "leases",
            createLeaseCollectionIfNotExists = true,
            connectionStringSetting = "AzureCosmosDBConnection") String[] items,
            final ExecutionContext context ) {
                context.getLogger().info(items.length + "item(s) is/are changed.");
            }

The following example shows an Azure Cosmos DB trigger TypeScript function. The function writes log messages when Azure Cosmos DB records are added or modified.

import { app, InvocationContext } from '@azure/functions';

export async function cosmosDBTrigger1(documents: unknown[], context: InvocationContext): Promise<void> {
    context.log(`Cosmos DB function processed ${documents.length} documents`);
}

app.cosmosDB('cosmosDBTrigger1', {
    connection: '<connection-app-setting>',
    databaseName: 'Tasks',
    containerName: 'Items',
    createLeaseContainerIfNotExists: true,
    handler: cosmosDBTrigger1,
});

TypeScript samples aren't documented for model v3.

The following example shows an Azure Cosmos DB trigger JavaScript function. The function writes log messages when Azure Cosmos DB records are added or modified.

const { app } = require('@azure/functions');

app.cosmosDB('cosmosDBTrigger1', {
    connection: '<connection-app-setting>',
    databaseName: 'Tasks',
    containerName: 'Items',
    createLeaseContainerIfNotExists: true,
    handler: (documents, context) => {
        context.log(`Cosmos DB function processed ${documents.length} documents`);
    },
});

The following example shows an Azure Cosmos DB trigger binding in a function.json file and a JavaScript function that uses the binding. The function writes log messages when Azure Cosmos DB records are added or modified.

Here's the binding data in the function.json file:

{
    "type": "cosmosDBTrigger",
    "name": "documents",
    "direction": "in",
    "leaseCollectionName": "leases",
    "connectionStringSetting": "<connection-app-setting>",
    "databaseName": "Tasks",
    "collectionName": "Items",
    "createLeaseCollectionIfNotExists": true
}

{
    "type": "cosmosDBTrigger",
    "name": "documents",
    "direction": "in",
    "leaseContainerName": "leases",
    "connection": "<connection-app-setting>",
    "databaseName": "Tasks",
    "containerName": "Items",
    "createLeaseContainerIfNotExists": true
}

Note that some of the binding attribute names changed in version 4.x of the Azure Cosmos DB extension.

Here's the JavaScript code:

    module.exports = async function (context, documents) {
      context.log('First document Id modified : ', documents[0].id);
    }

{
    "type": "cosmosDBTrigger",
    "name": "documents",
    "direction": "in",
    "leaseCollectionName": "leases",
    "connectionStringSetting": "<connection-app-setting>",
    "databaseName": "Tasks",
    "collectionName": "Items",
    "createLeaseCollectionIfNotExists": true
}

{
    "type": "cosmosDBTrigger",
    "name": "documents",
    "direction": "in",
    "leaseContainerName": "leases",
    "connection": "<connection-app-setting>",
    "databaseName": "Tasks",
    "containerName": "Items",
    "createLeaseContainerIfNotExists": true
}

import logging
import azure.functions as func

app = func.FunctionApp()

@app.function_name(name="CosmosDBTrigger")
@app.cosmos_db_trigger(name="documents", 
                       connection="CONNECTION_SETTING",
                       database_name="DB_NAME", 
                       container_name="CONTAINER_NAME", 
                       lease_container_name="leases",
                       create_lease_container_if_not_exists="true")
def test_function(documents: func.DocumentList) -> str:
    if documents:
        logging.info('Document id: %s', documents[0]['id'])

The function writes log messages when Azure Cosmos DB records are modified. Here's the binding data in the function.json file:

{
    "type": "cosmosDBTrigger",
    "name": "documents",
    "direction": "in",
    "leaseCollectionName": "leases",
    "connectionStringSetting": "<connection-app-setting>",
    "databaseName": "Tasks",
    "collectionName": "Items",
    "createLeaseCollectionIfNotExists": true
}

{
    "type": "cosmosDBTrigger",
    "name": "documents",
    "direction": "in",
    "leaseContainerName": "leases",
    "connection": "<connection-app-setting>",
    "databaseName": "Tasks",
    "containerName": "Items",
    "createLeaseContainerIfNotExists": true
}

Note that some of the binding attribute names changed in version 4.x of the Azure Cosmos DB extension.

Here's the Python code:

    import logging
    import azure.functions as func


    def main(documents: func.DocumentList) -> str:
        if documents:
            logging.info('First document Id modified: %s', documents[0]['id'])

Because of schema changes in the Azure Cosmos DB SDK, version 4.x of the Azure Cosmos DB extension requires azure-functions-java-library V3.0.0 for Java functions.

Use the @CosmosDBTrigger annotation on parameters that read data from Azure Cosmos DB. The annotation supports the following properties:

From the Java functions runtime library, use the @CosmosDBTrigger annotation on parameters that read data from Azure Cosmos DB. The annotation supports the following properties:

• name
• connectionStringSetting
• databaseName
• collectionName
• leaseConnectionStringSetting
• leaseDatabaseName
• leaseCollectionName
• createLeaseCollectionIfNotExists
• leasesCollectionThroughput
• leaseCollectionPrefix
• feedPollDelay
• leaseAcquireInterval
• leaseExpirationInterval
• leaseRenewInterval
• checkpointInterval
• checkpointDocumentCount
• maxItemsPerInvocation
• startFromBeginning
• preferredLocations

The following table explains the properties that you can set on the options object passed to the app.cosmosDB() method. The type, direction, and name properties don't apply to the v4 model.

The following table explains the binding configuration properties that you set in the function.json file, where properties differ by extension version:

See Binding types for a list of supported types.

See Binding types for a list of supported types.

When you want the function to process a single document, the Cosmos DB trigger can bind to the following types:

When you want the function to process a batch of documents, the Cosmos DB trigger can bind to the following types:

See Binding types for a list of supported types.