Creating an item in a Cosmos DB satellite region results in an error

[rwincewicz-alianza]

Bug Title

No response

Crate Name

azure_data_cosmos

Crate Version

0.22.1

Description

I have a Cosmos DB account set up with 3 regions (UK South - primary, UK West and West US 2) and multi-region writes are enabled.

If COSMOSDB_URL is either the global URL (e.g. https://testdb.documents.azure.com:443/) or the region-specific URL for the primary region (e.g. https://testdb-uksouth.documents.azure.com:443/) then I can create items in the database as expected. If I use the region-specific URL for either of the satellite regions (e.g. https://testdb-ukwest.documents.azure.com:443/ or https://testdb-westus2.documents.azure.com:443/) then I get the error The requested operation cannot be performed at this region.

If I conduct the same test with the Cosmos DB Python SDK then I can create an item in each of the regions without errors by providing the region-specific URL to CosmosClient. I've confirmed using the Azure Portal metrics that the requests are in fact going to the specified regions.

Steps to Reproduce

1. Create a Cosmos DB account with 3 regions (UK South - primary, UK West and West US 2), eventual consistency and multi-region writes are enabled.

2. Run the following code with COSMOSDB_URL as the URL of the primary region. I'm using the key_auth feature in the azure_data_cosmos crate for simplicity.

use azure_core::credentials::Secret;
use serde::{Serialize, Deserialize};
use azure_data_cosmos::{clients::ContainerClient, CosmosClient};

#[derive(Serialize, Deserialize, Debug)]
struct Item {
    pub id: String,
    pub partition_key: String,
    pub value: String,
}

async fn example() -> Result<(), Box<dyn std::error::Error>> {
    let item = Item {
        id: "1".into(),
        partition_key: "partition1".into(),
        value: "1".into(),
    };

    let cosmos_client: CosmosClient = CosmosClient::with_key("<COSMOSDB_URL>", Secret::from(<REDACTED>), None)?;
    
    let container: ContainerClient = cosmos_client.database_client("test").container_client("test");

    // Create an item
    container.create_item("1", item, None).await?;

    Ok(())
}

#[tokio::main]
async fn main() {
    let result = example().await;
    let _r = result.inspect(|x| println!("{:#?}", x)).inspect_err(|x| println!("{:#?}", x));
}

3. Confirm that the item has been created in the data explorer
4. Run the same code again but set COSMOSDB_URL to the URL of one of the satellite regions.
5. Observe the error The requested operation cannot be performed at this region

Checklist

• Follow our Code of Conduct
• Check that there isn't already an issue that request the same bug to avoid creating a duplicate.
• The provided reproduction is a minimal reproducible example of the bug.

[analogrelay]

At the moment, the Rust SDK doesn't support the x-ms-cosmos-allow-tentative-writes header required in order to write to the non-hub region. That's certainly something on our roadmap, but it's not present in this very early preview. You could use a custom policy to force the header in, but note that's not a tested and supported scenario at this time.

Thanks for the feedback though, we'll use this to help prioritize work as we continue to build out the official Rust SDK!

[rwincewicz-alianza]

Ah, good to know. Thanks for the explanation.

[rwincewicz-alianza]

I've just tested your suggestion of using a custom policy to set the x-ms-cosmos-allow-tentative-writes header and that worked nicely, thanks!