{"id":623,"date":"2020-03-25T10:00:21","date_gmt":"2020-03-25T17:00:21","guid":{"rendered":"https:\/\/devblogs.microsoft.com\/cosmosdb\/?p=623"},"modified":"2020-03-31T09:03:25","modified_gmt":"2020-03-31T16:03:25","slug":"java-sdk-v4-async-vs-sync","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/cosmosdb\/java-sdk-v4-async-vs-sync\/","title":{"rendered":"Azure Cosmos DB Java SDK v4 – Exploring the new Async API"},"content":{"rendered":"

In this second of our series for the Azure Cosmos DB<\/a> Java SDK v4 for Core (SQL) API, I\u2019m going to explore our new Async API.<\/span><\/p>\n

To get you caught up though go check out the first post in this series Azure Cosmos DB Java SDK v4 – New Java SDK Quickstart Guide and Sample Code!<\/a><\/span><\/p>\n

Current users of our Java SDK v2 are familiar with our Sync API and may have tried our Java SDK v3 with mixed results. We are really excited about our new Java SDK v4 because the performance is much better than our v3 SDK but also because the Java SDK v4 implements both an Async API and Sync API.<\/span><\/p>\n

If you are a Sync API user you may be wondering why would I want to use the Async API. The answer is that asynchronous calls will allow you to better saturate your available throughput. This is important because you always want to squeeze every ounce of performance for the provisioned throughput you are paying for.<\/span><\/p>\n

Another thing to understand about our new Async API is that it is built upon a Reactive programming<\/a> model. Reactive programming is a declarative programming data flow paradigm in which program operation and control flow are described as a stream of data items passing through a pipeline of operations in which each operation affects the data which flows downstream. In practical terms, your code will describe a directed graph of operations which represents the logic of the program. Here\u2019s a simple declarative data flow in pseudo-code:<\/span><\/p>\n

asynchronous data source => operation1 => operation2 => operation3 => print<\/span><\/p>\n

With the Async API, Java SDK 4.0 requires that you use\u00a0Reactor<\/a>\u00a0framework to describe the logic of your application. In the rest of this post. I\u2019ll demonstrate some common Cosmos DB tasks with Async API and Reactor. Then I\u2019ll show the same tasks with Sync API for comparison. When you’re done, take a look at our new Reactor Pattern Guide<\/a> to help you get started with Reactive Programming!<\/span><\/p>\n

Note: <\/strong>Real Azure Cosmos DB performance test results are shown below. Reproducing them will incur container throughput and storage costs<\/a>.<\/p>\n

Async API<\/strong><\/span><\/h2>\n

The Async API sends requests to Azure Cosmos DB using Reactor Netty<\/a> with asynchronous I\/O at the OS level \u2013 therefore your application won\u2019t block waiting for the response to each request. Instead your application will push out as many requests per second as your system hardware and your\u00a0provisioned throughput<\/a>\u00a0allow. Meanwhile responses from the server will be handled as they arrive. This raises the upper bound on request throughput substantially.<\/p>\n

This code is from the Async Request Throughput sample<\/a>. Here is an example of creating a new database- and container-if not-exists and then inserting new items using the Async API. Clients, databases, and containers have special async types in Java SDK v4 (like CosmosAsyncClient<\/span> below.) Notice the time between request and response is used to run background tasks.<\/span><\/p>\n