Find the request unit charge for operations executed in Azure Cosmos DB for Apache Cassandra

APPLIES TO: Cassandra

Azure Cosmos DB supports many APIs, such as SQL, MongoDB, Cassandra, Gremlin, and Table. Each API has its own set of database operations. These operations range from simple point reads and writes to complex queries. Each database operation consumes system resources based on the complexity of the operation.

The cost of all database operations is normalized by Azure Cosmos DB and is expressed by Request Units (or RUs, for short). Request charge is the request units consumed by all your database operations. You can think of RUs as a performance currency abstracting the system resources such as CPU, IOPS, and memory that are required to perform the database operations supported by Azure Cosmos DB. No matter which API you use to interact with your Azure Cosmos DB container, costs are always measured by RUs. Whether the database operation is a write, point read, or query, costs are always measured in RUs. To learn more, see the request units and it's considerations article.

This article presents the different ways you can find the request unit (RU) consumption for any operation executed against a container in Azure Cosmos DB for Apache Cassandra. If you are using a different API, see API for MongoDB, API for NoSQL, API for Gremlin, and API for Table articles to find the RU/s charge.

When you perform operations against the Azure Cosmos DB for Apache Cassandra, the RU charge is returned in the incoming payload as a field named RequestCharge. You have multiple options for retrieving the RU charge.

Use a Cassandra Driver

.NET Driver

When you use the .NET SDK, you can retrieve the incoming payload under the Info property of a RowSet object:

RowSet rowSet = session.Execute("SELECT table_name FROM system_schema.tables;");
double requestCharge = BitConverter.ToDouble(rowSet.Info.IncomingPayload["RequestCharge"].Reverse().ToArray(), 0);

For more information, see Quickstart: Build a Cassandra app by using the .NET SDK and Azure Cosmos DB.

Java Driver

When you use the Java SDK, you can retrieve the incoming payload by calling the getExecutionInfo() method on a ResultSet object:

ResultSet resultSet = session.execute("SELECT table_name FROM system_schema.tables;");
Double requestCharge = resultSet.getExecutionInfo().getIncomingPayload().get("RequestCharge").getDouble();

For more information, see Quickstart: Build a Cassandra app by using the Java SDK and Azure Cosmos DB.

GOCQL Driver

When you use the GOCQL driver, you can retrieve the incoming payload by calling the GetCustomPayload() method on a Iter type:

query := session.Query(fmt.Sprintf("SELECT * FROM <keyspace.table> where <value> = ?", keyspace, table)).Bind(<value>)
iter := query.Iter()
requestCharge := iter.GetCustomPayload()["RequestCharge"]
requestChargeBits := binary.BigEndian.Uint64(requestCharge)
requestChargeValue := math.Float64frombits(requestChargeBits)
fmt.Printf("%v\n", requestChargeValue)

For more information, see Quickstart: Build a Cassandra app by using GOCQL and Azure Cosmos DB.

Next steps

To learn about optimizing your RU consumption, see these articles:

• Request units and throughput in Azure Cosmos DB
• Optimize provisioned throughput cost in Azure Cosmos DB
• Optimize query cost in Azure Cosmos DB