Azure Function output binding to Cosmos DB error with PartitionKey

Question

I'm trying to make an Azure Function run with CosmosDB output binding.

The trigger is HTTP, the DB is defined with SQL API.

Here is my code:

[FunctionName("ProcessOrderCosmos")]
public static void Run(
    [HttpTrigger(AuthorizationLevel.Anonymous, "post", Route = null)] HttpRequest req,
    [CosmosDB(
         databaseName: "myDB",
         collectionName: "items",
         ConnectionStringSetting = "CosmosDBConnection")]out Item item,
    ILogger log)
    {
        string requestBody = new StreamReader(req.Body).ReadToEndAsync().Result;  

        item=JsonConvert.DeserializeObject<Item>(requestBody);  
    }

However, the function shows the following error:

PartitionKey extracted from document doesn't match the one specified in the header

What is the problem? Since I'm using the binding, I have no control over the payload sent to the server, and don't have access to the headers.

What am I missing?

DSpirit DSpirit · Accepted Answer · 2020-11-26T13:29:23

Since you have created the collection with a partition key, you need your Item object to include this field. So if you have chosen let's say id as partition key, your model needs to include the property.

Azure Function output binding to Cosmos DB error with PartitionKey

2 Answers