AWS Big Data Blog
Amazon Kinesis Data Streams on-demand capacity mode now scales up to 1 GB/second ingest capacity
Amazon Kinesis Data Streams is a serverless data streaming service that makes it easy to capture, process, and store streaming data at any scale. As customers collect and stream more types of data, they have asked for simpler, elastic data streams that can handle variable and unpredictable data traffic. In November 2021, Amazon Web Services launched the on-demand capacity mode for Kinesis Data Streams, which is capable of serving gigabytes of write and read throughput per minute and helps reduce the operational pain point of manually updating data stream capacity. You can create a new on-demand data stream or convert an existing data stream to on-demand mode with a single click and never have to provision and manage servers, storage, or throughput. By default, on-demand capacity mode can automatically scale up to 200 MB/s of write throughput.
We were encouraged by customers’ adoption of on-demand capacity mode, but as customers scaled their workloads, some ran into the 200 MB/s data ingestion limit and asked for a solution. The team worked backward from customer feedback to raise that limit. As of March 2023, Kinesis Data Streams supports an increased on-demand write throughput limit to 1 GB/s, a five-times increase from the current limit of 200 MB/s. It’s like having a truly serverless and elastic data streaming service that works for all your use cases. If you require an increase in capacity, you can contact AWS Support to enable on-demand streams to scale up to 1 GB/s write throughput for each requested account. You pay for throughput consumed rather than for provisioned resources, making it easier to balance costs and performance. Overall, if your data volume can spike unpredictably or you don’t want to manage the number of shards, use on-demand streams.
In this post, we explore how to use Kinesis Data Streams on-demand scaling and best practices to build an efficient data-streaming solution. We discuss different scenarios to avoid write throughput exceptions and scale ingest capacity of Kinesis Data Streams to 1 GB/s in on-demand capacity mode.
Kinesis Data Streams on-demand scaling
A shard serves as a base throughput unit of Kinesis Data Streams. A shard supports 1 MB/s and 1,000 records/s for writes and 2 MB/s for reads. The shard limits ensure predictable performance, making it easy to design and operate a highly reliable data streaming workflow. In on-demand capacity mode, scaling happens at the individual shard level. When the average ingest shard utilization reaches 50% (0.5 MB/s or 500 records/s) in 1 minute, then a shard is split into two shards. If you use random values as a partition key, all shards of the stream will have even traffic, and they will be scaled at the same time. If you use a business-specific key as a partition key, the shards will have uneven traffic. In that scenario, only the shards exceeding an average of 50% utilization will be scaled. Depending upon the number of shards being scaled, it will take up to 15 minutes to split the shards.
When we create a new Kinesis data stream in on-demand capacity mode, by default, Kinesis Data Streams provisions four shards, which provides 4 MB/s write and 8 MB/s read throughput. As the workload ramps up, Kinesis Data Streams increases the number of shards in the stream by monitoring ingest throughput at the shard level. The 4 MB/s default ingest throughput and scaling at shard level in on-demand capacity mode works for most use cases. However, in some specific scenarios, producers may face WriteThroughputExceeded and Rate Exceeded errors, even in on-demand capacity mode. We discuss a few of these scenarios in the following sections and strategies to avoid these errors.
You can create and save record templates and easily send data to Kinesis Data Streams using the Amazon Kinesis Data Generator (KDG) to test the streaming data solution. Alternatively, you can also use the modern load testing framework Locust to run large-scale Kinesis Data Streams load testing. For this post, we use the Locust tool to produce and ingest messages in Kinesis Data Streams for our different use cases.
Scenario 1: A baseline ingest throughput greater than 4 MB/s is needed
To simulate this scenario, run the following AWS Command Line Interface (AWS CLI) command to create the kds-od-default-shards data stream in on-demand capacity mode:
When the kds-od-default-shards data stream is active, run following AWS CLI command to check the number of shards in the data stream:
You can observe that the OpenShardCount value is 4, which means the kds-od-default-shards data stream has an ingest capacity of 4 MB/s.
Next, we use the Locust tool to set the baseline to approximately 25 MB/s records. As displayed in the following Amazon CloudWatch metrics graph, records are getting throttled for the first couple of minutes. Then the kds-od-default-shards data stream scales the number of shards to support 25 MB/s ingest throughput, and records stop getting throttled. You can also rerun the describe-stream-summary AWS CLI command to check the increased number of shards in the data stream.
In a scenario where we know our ingest throughput baseline (25 MB/s) ahead of the time and we don’t want to observe any write throttles, we can create a stream in provisioned mode by specifying the number of shards (30), as shown in the following AWS CLI command (make sure to delete kds-od-default-shards manually from the Kinesis Data Streams console before running the following command):
When the kds-od-default-shards data stream is active, run the following AWS CLI command to convert the data stream’s capacity mode to on-demand:
Next, we send 25 MB/s records to the kds-od-default-shards data stream. As displayed in the following CloudWatch metrics graph, we can observe no write throttles, and the kds-od-default-shards data stream scales the number of shards to handle the increase in ingest volume.
After we send 25 MB/s traffic to the data stream for some time, we can run following AWS CLI command to see that the OpenShardCount value is increased to more than 30 now:
Scenario 2: A significant ingestion spike is expected, which needs ingest throughput greater than the number of shards in the stream
To simulate the scenario, run the following AWS CLI command to create the kds-od-significant-spike data stream in on-demand capacity mode:
As mentioned earlier, by default, the kds-od-significant-spike data stream will have four shards initially because this stream is created in on-demand mode. When the data stream is active, we send 4 MB/s ingest throughput initially and grow the ingest throughput by 30–50% every 5–10 minutes. As displayed in the following CloudWatch metrics graph, the kds-od-significant-spike data stream scales the number of shards to handle the increase in ingest volume.
After approximately 15 minutes, run the following AWS CLI command to find the OpenShardCount value (x) of the kds-od-significant-spike data stream. Then send (x * 2) MB/s ingest throughput in the data stream for 2–3 minutes and reduced ingest throughput to the prior level:
As displayed in the following CloudWatch metrics graph, the records are getting throttled for a few minutes, and then the throttling goes away.
Typically, we face a significant spike scenario when running planned events, such as shopping holidays and product launches. To handle such scenarios, we can proactively change capacity mode from on-demand to provisioned. We can configure the number of shards and pick the ingest capacity we anticipate. After we successfully scale the number of shards to our desired peak capacity in provisioned capacity mode, we can change the capacity mode back to on-demand mode.
Scenario 3: A single partition key starts pushing more than 1 MB/s
Partition keys are used to segregate and route records to different shards of a stream. A partition key is specified by the data producer while adding data to the data stream. For example, let’s assume we have a stream with two shards (shard 1 and shard 2). We can configure the data producer to use two partition keys (key A and key B) so that all records with key A are added to shard 1 and all records with key B are added to shard 2. Choosing a partition key is a very important decision, and we should carefully pick the partition key to ensure equal distribution of records across all the shards of the stream. Messages tied to a single partition key A will be sent to a single shard (shard 1), and at any given instance, messages tied to a single partition key A cannot be distributed across different shards. As mentioned earlier, by default, one shard supports 1 MB/s and 1,000 records/s for writes, and we may end up with an edge case scenario where we are trying to push more than 1 MB/s for a specific partition key. In this scenario, producers will continue to experience throttles and keep retrying indefinitely.
To simulate the scenario, run the following AWS CLI command to create the kds-od-partition-key-throttle data stream in on-demand capacity mode:
As mentioned earlier, by default, the data stream will have four shards initially because this stream is created in on-demand mode. When the data stream is active, we send 1.5 MB/s ingest throughput continuously for the specific partition key A. As displayed in the following CloudWatch metrics graph, we can observe that throttling continues from a single shard even if we are sending 1.5 MB/s ingest throughput, and the kds-od-partition-key-throttle data stream has an overall ingest capacity of 4 MB/s.
To avoid this scenario, we should carefully pick our partition key and ensure that this specific partition key won’t be continuously sending more than 1 MB/s ingest throughput in the data stream.
Scale the ingest capacity of Kinesis Data Streams to 1 GB/s in on-demand capacity mode
To test, we start with approximately 100 MB/s baseline ingest throughput to Kinesis Data Streams in on-demand capacity mode, then we increase ingest throughput rate by 30–50% every 5–10 minutes using Locust load testing tool.
To set up the scenario, first create the kds-od-1gb-stream data stream in provisioned capacity mode and provide a value of 120 for the provisioned shards field:
When the kds-od-1gb-stream data stream is active, switch its capacity mode to on-demand, as shown in the following code. When we change capacity mode from provisioned to on-demand, the shard count (120) remains the same for the data stream even in on-demand capacity mode.
When the kds-od-1gb-stream data stream is in on-demand mode, start the experiment. We send approximately 100 MB/s baseline ingest throughput using the Locust tool and increase 30–50% ingest throughput every 5–10 minutes. As displayed in the following CloudWatch metrics graph, the kds-od-1gb-stream data stream seamlessly scaled to 1 GB/s in on-demand capacity mode. We can also observe that the producers didn’t encounter any write throttles while the data stream was scaling in on-demand capacity mode.
Clean up
To avoid ongoing costs, delete all the data streams that you created as part of this post using the Kinesis Data Streams console.
Conclusion
This post demonstrated the on-demand scaling policy of Kinesis Data Streams with a few scenarios using best practices and showed how to scale ingest capacity to 1 GB/s in on-demand capacity mode. You can have an on-demand write throughput limit that is five times larger than the previous limit of 200 MB/s. Choose on-demand mode if you create new data streams with unknown workloads, have unpredictable application traffic, or prefer not to manage capacity. You can switch between on-demand and provisioned capacity modes two times per 24-hour rolling period. Please leave any feedback in the comments section.
About the Authors
Nihar Sheth is a Senior Product Manager on the Amazon Kinesis Data Streams team at Amazon Web Services. He is passionate about developing intuitive product experiences that solve complex customer problems and enable customers to achieve their business goals.
Pratik Patel is Sr. Technical Account Manager and streaming analytics specialist. He works with AWS customers and provides ongoing support and technical guidance to help plan and build solutions using best practices and proactively keep customers’ AWS environments operationally healthy.
Nisha Dekhtawala is a Partner Solutions Architect and data analytics specialist. She works with global consulting partners as their trusted advisor, providing technical guidance and support in building Well-Architected innovative industry solutions.