title | description | ms.topic | ms.date | ms.devlang | ms.custom | zone_pivot_groups |
---|---|---|---|---|---|---|
Azure Cosmos DB trigger for Functions 2.x and higher |
Learn to use the Azure Cosmos DB trigger in Azure Functions. |
reference |
01/19/2024 |
csharp |
devx-track-csharp, devx-track-python, devx-track-extended-java, devx-track-js, devx-track-ts |
programming-languages-set-functions |
The Azure Cosmos DB Trigger uses the Azure Cosmos DB change feed to listen for inserts and updates across partitions. The change feed publishes new and updated items, not including updates from deletions.
For information on setup and configuration details, see the overview.
Cosmos DB scaling decisions for the Consumption and Premium plans are done via target-based scaling. For more information, see Target-based scaling.
::: zone pivot="programming-language-javascript,programming-language-typescript" [!INCLUDE functions-nodejs-model-tabs-description] ::: zone-end ::: zone pivot="programming-language-python" [!INCLUDE functions-bindings-python-models-intro]
::: zone-end
::: zone pivot="programming-language-csharp"
The usage of the trigger depends on the extension package version and the C# modality used in your function app, which can be one of the following:
An isolated worker process class library compiled C# function runs in a process isolated from the runtime.
[!INCLUDE functions-in-process-model-retirement-note]
An in-process class library is a compiled C# function runs in the same process as the Functions runtime.
The following examples depend on the extension version for the given C# mode.
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:
:::code language="csharp" source="~/azure-functions-dotnet-worker/samples/Extensions/CosmosDB/CosmosDBFunction.cs" range="49-58":::
An IReadOnlyList<T>
is used as the Azure Cosmos DB trigger binding parameter in the following example:
:::code language="csharp" source="~/azure-functions-dotnet-worker/samples/Extensions/CosmosDB/CosmosDBFunction.cs" id="docsnippet_exponential_backoff_retry_example":::
This example requires the following using
statements:
:::code language="csharp" source="~/azure-functions-dotnet-worker/samples/Extensions/CosmosDB/CosmosDBFunction.cs" range="4-7":::
::: zone-end ::: zone pivot="programming-language-java"
This function is invoked when there are inserts or updates in the specified database and container.
[!INCLUDE functions-cosmosdb-extension-java-note]
@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.");
}
In the Java functions runtime library, use the @CosmosDBTrigger
annotation on parameters whose value would come from Azure Cosmos DB. This annotation can be used with native Java types, POJOs, or nullable values using Optional<T>
.
::: zone-end
::: zone pivot="programming-language-typescript"
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.
:::code language="typescript" source="~/azure-functions-nodejs-v4/ts/src/functions/cosmosDBTrigger1.ts" :::
TypeScript samples aren't documented for model v3.
::: zone-end
::: zone pivot="programming-language-javascript"
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.
:::code language="javascript" source="~/azure-functions-nodejs-v4/js/src/functions/cosmosDBTrigger1.js" :::
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:
[!INCLUDE functions-cosmosdb-trigger-attributes]
Here's the JavaScript code:
module.exports = async function (context, documents) {
context.log('First document Id modified : ', documents[0].id);
}
::: zone-end
::: zone pivot="programming-language-powershell"
The following example shows how to run a function as data changes in Azure Cosmos DB.
[!INCLUDE functions-cosmosdb-trigger-attributes]
In the run.ps1 file, you have access to the document that triggers the function via the $Documents
parameter.
param($Documents, $TriggerMetadata)
Write-Host "First document Id modified : $($Documents[0].id)"
::: zone-end
::: zone pivot="programming-language-python"
The following example shows an Azure Cosmos DB trigger binding. The example depends on whether you use the v1 or v2 Python programming model.
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:
[!INCLUDE functions-cosmosdb-trigger-attributes]
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'])
::: zone-end
::: zone pivot="programming-language-csharp"
Both in-process and isolated process C# libraries use the CosmosDBTriggerAttribute to define the function. C# script instead uses a function.json configuration file as described in the C# scripting guide.
[!INCLUDE functions-cosmosdb-attributes-v4]
[!INCLUDE functions-cosmosdb-attributes-v3]
[!INCLUDE functions-cosmosdb-attributes-v4]
[!INCLUDE functions-cosmosdb-attributes-v3]
::: zone-end
::: zone pivot="programming-language-python"
Applies only to the Python v2 programming model.
For Python v2 functions defined using a decorator, the following properties on the cosmos_db_trigger
:
Property | Description |
---|---|
arg_name |
The variable name used in function code that represents the list of documents with changes. |
database_name |
The name of the Azure Cosmos DB database with the collection being monitored. |
collection_name |
The name of the Azure Cosmos DB collection being monitored. |
connection |
The connection string of the Azure Cosmos DB being monitored. |
For Python functions defined by using function.json, see the Configuration section. ::: zone-end
::: zone pivot="programming-language-java"
[!INCLUDE functions-cosmosdb-extension-java-note]
Use the @CosmosDBTrigger
annotation on parameters that read data from Azure Cosmos DB. The annotation supports the following properties:
Attribute property | Description |
---|---|
connection | The name of an app setting or setting collection that specifies how to connect to the Azure Cosmos DB account being monitored. For more information, see Connections. |
name | The name of the function. |
databaseName | The name of the Azure Cosmos DB database with the container being monitored. |
containerName | The name of the container being monitored. |
leaseConnectionStringSetting | (Optional) The name of an app setting or setting collection that specifies how to connect to the Azure Cosmos DB account that holds the lease container. When not set, the Connection value is used. This parameter is automatically set when the binding is created in the portal. The connection string for the leases container must have write permissions. |
leaseDatabaseName | (Optional) The name of the database that holds the container used to store leases. When not set, the value of the databaseName setting is used. |
leaseContainerName | (Optional) The name of the container used to store leases. When not set, the value leases is used. |
createLeaseContainerIfNotExists | (Optional) When set to true , the leases container is automatically created when it doesn't already exist. The default value is false . When using Microsoft Entra identities if you set the value to true , creating containers isn't an allowed operation and your Function won't start. |
leasesContainerThroughput | (Optional) Defines the number of Request Units to assign when the leases container is created. This setting is only used when CreateLeaseContainerIfNotExists is set to true . This parameter is automatically set when the binding is created using the portal. |
leaseContainerPrefix | (Optional) When set, the value is added as a prefix to the leases created in the Lease container for this function. Using a prefix allows two separate Azure Functions to share the same Lease container by using different prefixes. |
feedPollDelay | (Optional) The time (in milliseconds) for the delay between polling a partition for new changes on the feed, after all current changes are drained. Default is 5,000 milliseconds, or 5 seconds. |
leaseAcquireInterval | (Optional) When set, it defines, in milliseconds, the interval to kick off a task to compute if partitions are distributed evenly among known host instances. Default is 13000 (13 seconds). |
leaseExpirationInterval | (Optional) When set, it defines, in milliseconds, the interval for which the lease is taken on a lease representing a partition. If the lease isn't renewed within this interval, it will expire and ownership of the partition moves to another instance. Default is 60000 (60 seconds). |
leaseRenewInterval | (Optional) When set, it defines, in milliseconds, the renew interval for all leases for partitions currently held by an instance. Default is 17000 (17 seconds). |
maxItemsPerInvocation | (Optional) When set, this property sets the maximum number of items received per Function call. If operations in the monitored container are performed through stored procedures, transaction scope is preserved when reading items from the change feed. As a result, the number of items received could be higher than the specified value so that the items changed by the same transaction are returned as part of one atomic batch. |
startFromBeginning | (Optional) This option tells the Trigger to read changes from the beginning of the container's change history instead of starting at the current time. Reading from the beginning only works the first time the trigger starts, as in subsequent runs, the checkpoints are already stored. Setting this option to true when there are leases already created has no effect. |
preferredLocations | (Optional) Defines preferred locations (regions) for geo-replicated database accounts in the Azure Cosmos DB service. Values should be comma-separated. For example, "East US,South Central US,North Europe". |
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
::: zone-end
::: zone pivot="programming-language-javascript,programming-language-typescript,programming-language-powershell,programming-language-python"
::: zone-end
::: zone pivot="programming-language-python" Applies only to the Python v1 programming model.
::: zone-end ::: zone pivot="programming-language-javascript,programming-language-typescript"
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:
::: zone-end ::: zone pivot="programming-language-powershell,programming-language-python"
The following table explains the binding configuration properties that you set in the function.json file, where properties differ by extension version:
::: zone-end ::: zone pivot="programming-language-javascript,programming-language-typescript,programming-language-powershell,programming-language-python"
[!INCLUDE functions-cosmosdb-settings-v4]
[!INCLUDE functions-cosmosdb-settings-v3]
::: zone-end
See the Example section for complete examples.
The trigger requires a second collection that it uses to store leases over the partitions. Both the collection being monitored and the collection that contains the leases must be available for the trigger to work.
::: zone pivot="programming-language-csharp"
Important
If multiple functions are configured to use an Azure Cosmos DB trigger for the same collection, each of the functions should use a dedicated lease collection or specify a different LeaseCollectionPrefix
for each function. Otherwise, only one of the functions is triggered. For information about the prefix, see the Attributes section.
::: zone-end
::: zone pivot="programming-language-java"
[!IMPORTANT]
If multiple functions are configured to use an Azure Cosmos DB trigger for the same collection, each of the functions should use a dedicated lease collection or specify a different leaseCollectionPrefix
for each function. Otherwise, only one of the functions is triggered. For information about the prefix, see the Annotations section.
::: zone-end
::: zone pivot="programming-language-javascript,programming-language-typescript,programming-language-powershell,programming-language-python"
[!IMPORTANT]
If multiple functions are configured to use an Azure Cosmos DB trigger for the same collection, each of the functions should use a dedicated lease collection or specify a different leaseCollectionPrefix
for each function. Otherwise, only one of the functions will be triggered. For information about the prefix, see the Configuration section.
::: zone-end
The trigger doesn't indicate whether a document was updated or inserted, it just provides the document itself. If you need to handle updates and inserts differently, you could do that by implementing timestamp fields for insertion or update.
::: zone pivot="programming-language-csharp"
The parameter type supported by the Azure Cosmos DB trigger depends on the Functions runtime version, the extension package version, and the C# modality used.
See Binding types for a list of supported types.
See Binding types for a list of supported types.
[!INCLUDE functions-bindings-cosmosdb-v2-trigger-dotnet-isolated-types]
See Binding types for a list of supported types.
::: zone-end
[!INCLUDE functions-cosmosdb-connections]