storing object in cosmos db returns bad request?

Question

I seem to be unable to store a simple object to cosmos db?

this is the database model.

public class HbModel
{
    public Guid id { get; set; }

    public string FormName { get; set; }
    
    public Dictionary<string, object> Form { get; set; }
}

and this is how I store the data into the database

private static void SeedData(HbModelContext dbContext)
{
    var cosmosClient = dbContext.Database.GetCosmosClient();  
    cosmosClient.ClientOptions.AllowBulkExecution = true;

    if (dbContext.Set<HbModel>().FirstOrDefault() == null)
    {
        // No items could be picked hence try seeding.
        var container = cosmosClient.GetContainer("hb", "hb_forms");
        HbModel first = new HbModel()
       {
                Id = Guid.NewGuid(),//Guid.Parse(x["guid"] as string),
                FormName = "asda",//x["name"] as string,
                Form = new Dictionary<string, object>() // 
        }
        
        string partitionKey = await GetPartitionKey(container.Database, container.Id);
        var response = await container.CreateItemAsync(first, new PartitionKey(partitionKey));
    }
    else
    {
        Console.WriteLine("Already have data");
    }
}


private static async Task<string> GetPartitionKey(Database database, string containerName)
{
    var query = new QueryDefinition("select * from c where c.id = @id")
        .WithParameter("@id", containerName);
    using var iterator = database.GetContainerQueryIterator<ContainerProperties>(query);

    while (iterator.HasMoreResults)
    {
        foreach (var container in await iterator.ReadNextAsync())
        {
            return container.PartitionKeyPath;
        }
    }

    return null;
}

but when creating the item I get this error message

A host error has occurred during startup operation '3b06df1f-000c-4223-a374-ca1dc48d59d1'.
[2022-07-11T15:02:12.071Z] Microsoft.Azure.Cosmos.Client: Response status code does not indicate success: BadRequest (400); Substatus: 0; ActivityId: 24bac0ba-f1f7-411f-bc57-3f91110c4528; Reason: ();.
Value cannot be null. (Parameter 'provider')

no idea why it fails? the data should not be formatted incorreclty? It also fails in case there is data in the dictionary.

What is going wrong?

Answer 1

There are several things wrong with the attached code.

1. You are enabling Bulk but you are not following the Bulk pattern

cosmosClient.ClientOptions.AllowBulkExecution = true is being set, but you are not parallelizing work. If you are going to use Bulk, make sure you are following the documentation and creating lists of concurrent Tasks. Reference: https://learn.microsoft.com/azure/cosmos-db/sql/tutorial-sql-api-dotnet-bulk-import#step-6-populate-a-list-of-concurrent-tasks. Otherwise don't use Bulk.

2. You are blocking threads.

The call to container.CreateItemAsync(first, new PartitionKey("/__partitionKey")).Result; is a blocking call, this can lead you to deadlocks. When using async operations (such as CreateItemAsync) please use the async/await pattern. Reference: https://github.com/davidfowl/AspNetCoreDiagnosticScenarios/blob/master/AsyncGuidance.md#avoid-using-taskresult-and-taskwait

3. The PartitionKey parameter should be the value not the definition.

On the call container.CreateItemAsync(first, new PartitionKey("/__partitionKey")) the Partition Key (second parameter) should be the value. Assuming your container has a Partition Key Definition of /__partitionKey then your documents should have a __partitionKey property and you should pass the Value in this parameter of such property in the current document. Reference: https://learn.microsoft.com/azure/cosmos-db/sql/troubleshoot-bad-request#wrong-partition-key-value

Optionally, if your documents do not contain such a value, just remove the parameter from the call:

container.CreateItemAsync(first)

Be advised though that this solution will not scale, you need to design your database with Partitioning in mind: https://learn.microsoft.com/azure/cosmos-db/partitioning-overview#choose-partitionkey

4. Missing id

The model has Id but Cosmos DB requires id, make sure the content of the document contains id when serialized.