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Amazon Kinesis Streams
Developer Guide

Amazon Kinesis Streams Key Concepts

As you get started with Amazon Kinesis Streams, you'll benefit from understanding its architecture and terminology.

Kinesis Streams High-level Architecture

The following diagram illustrates the high-level architecture of Kinesis Streams. The producers continually push data to Kinesis Streams and the consumers process the data in real time. Consumers (such as a custom application running on Amazon EC2, or an Amazon Kinesis Firehose delivery stream) can store their results using an AWS service such as Amazon DynamoDB, Amazon Redshift, or Amazon S3.


					Kinesis Streams High-level Architecture Diagram

Kinesis Streams Terminology

Kinesis Streams

An Kinesis stream is an ordered sequence of data records. Each record in the stream has a sequence number that is assigned by Kinesis Streams. The data records in the stream are distributed into shards.

Data Records

A data record is the unit of data stored in an Kinesis stream. Data records are composed of a sequence number, partition key, and data blob, which is an immutable sequence of bytes. Kinesis Streams does not inspect, interpret, or change the data in the blob in any way. A data blob can be up to 1 MB.

Retention Period

The length of time data records are accessible after they are added to the stream. A stream’s retention period is set to a default of 24 hours after creation. You can increase the retention period up to 168 hours (7 days) using the IncreaseStreamRetentionPeriod operation, and decrease the retention period down to a minimum of 24 hours using the DecreaseStreamRetentionPeriod operation. Additional charges apply for streams with a retention period set above 24 hours. For more information, see Amazon Kinesis Streams Pricing.

Producers

Producers put records into Amazon Kinesis Streams. For example, a web server sending log data to a stream is a producer.

Consumers

Consumers get records from Amazon Kinesis Streams and process them. These consumers are known as Amazon Kinesis Streams Applications.

Amazon Kinesis Streams Applications

An Amazon Kinesis Streams application is a consumer of a stream that commonly runs on a fleet of EC2 instances.

You can develop an Amazon Kinesis Streams application using the Kinesis Client Library or using the Kinesis Streams API.

The output of an Amazon Kinesis Streams application may be input for another stream, enabling you to create complex topologies that process data in real time. An application can also send data to a variety of other AWS services. There can be multiple applications for one stream, and each application can consume data from the stream independently and concurrently.

Shards

A shard is a uniquely identified group of data records in a stream. A stream is composed of one or more shards, each of which provides a fixed unit of capacity. Each shard can support up to 5 transactions per second for reads, up to a maximum total data read rate of 2 MB per second and up to 1,000 records per second for writes, up to a maximum total data write rate of 1 MB per second (including partition keys). The data capacity of your stream is a function of the number of shards that you specify for the stream. The total capacity of the stream is the sum of the capacities of its shards.

If your data rate increases, you can increase or decrease the number of shards allocated to your stream.

Partition Keys

A partition key is used to group data by shard within a stream. The Kinesis Streams service segregates the data records belonging to a stream into multiple shards, using the partition key associated with each data record to determine which shard a given data record belongs to. Partition keys are Unicode strings with a maximum length limit of 256 bytes. An MD5 hash function is used to map partition keys to 128-bit integer values and to map associated data records to shards. A partition key is specified by the applications putting the data into a stream.

Sequence Numbers

Each data record has a sequence number that is unique within its shard. The sequence number is assigned by Kinesis Streams after you write to the stream with client.putRecords or client.putRecord. Sequence numbers for the same partition key generally increase over time; the longer the time period between write requests, the larger the sequence numbers become.

Note

Sequence numbers cannot be used as indexes to sets of data within the same stream. To logically separate sets of data, use partition keys or create a separate stream for each data set.

Kinesis Client Library

The Kinesis Client Library is compiled into your application to enable fault-tolerant consumption of data from the stream. The Kinesis Client Library ensures that for every shard there is a record processor running and processing that shard. The library also simplifies reading data from the stream. The Kinesis Client Library uses an Amazon DynamoDB table to store control data. It creates one table per application that is processing data.

Application Name

The name of an Amazon Kinesis Streams application identifies the application. Each of your applications must have a unique name that is scoped to the AWS account and region used by the application. This name is used as a name for the control table in Amazon DynamoDB and the namespace for Amazon CloudWatch metrics.

Server-side encryption

Amazon Kinesis Streams can automatically encrypt sensitive data as a producer enters it into a stream. Kinesis Streams uses KMS master keys for encryption. For more information, see Using Server-Side Encryption.

Note

To read from or write to an encrypted stream, producer and consumer applications must have permission to access the master key. For information on granting permissions to producer and consumer applications, see Permissions to Use User-Generated KMS Master Keys.

Note

Using server-side encryption will incur KMS costs. For more information, see AWS Key Management Service Pricing.