Amazon Kinesis Service API Reference
API Reference (API Version 2013-12-02)
« PreviousNext »
View the PDF for this guide.Go to the AWS Discussion Forum for this product.Did this page help you?  Yes | No |  Tell us about it...

MergeShards

Merges two adjacent shards in a stream and combines them into a single shard to reduce the stream's capacity to ingest and transport data. Two shards are considered adjacent if the union of the hash key ranges for the two shards form a contiguous set with no gaps. For example, if you have two shards, one with a hash key range of 276...381 and the other with a hash key range of 382...454, then you could merge these two shards into a single shard that would have a hash key range of 276...454. After the merge, the single child shard receives data for all hash key values covered by the two parent shards.

MergeShards is called when there is a need to reduce the overall capacity of a stream because of excess capacity that is not being used. You must specify the shard to be merged and the adjacent shard for a stream. For more information about merging shards, see Merge Two Shards in the Amazon Kinesis Developer Guide.

If the stream is in the ACTIVE state, you can call MergeShards. If a stream is in the CREATING, UPDATING, or DELETING state, MergeShards returns a ResourceInUseException. If the specified stream does not exist, MergeShards returns a ResourceNotFoundException.

You can use DescribeStream to check the state of the stream, which is returned in StreamStatus.

MergeShards is an asynchronous operation. Upon receiving a MergeShards request, Amazon Kinesis immediately returns a response and sets the StreamStatus to UPDATING. After the operation is completed, Amazon Kinesis sets the StreamStatus to ACTIVE. Read and write operations continue to work while the stream is in the UPDATING state.

You use DescribeStream to determine the shard IDs that are specified in the MergeShards request.

If you try to operate on too many streams in parallel using CreateStream, DeleteStream, MergeShards or SplitShard, you will receive a LimitExceededException.

MergeShards has limit of 5 transactions per second per account.

Request Syntax

{
    "AdjacentShardToMerge": "string",
    "ShardToMerge": "string",
    "StreamName": "string"
}
			

Request Parameters

For information about the common parameters that all actions use, see Common Parameters.

The request accepts the following data in JSON format.

AdjacentShardToMerge

The shard ID of the adjacent shard for the merge.

Type: String

Length constraints: Minimum length of 1. Maximum length of 128.

Required: Yes

ShardToMerge

The shard ID of the shard to combine with the adjacent shard for the merge.

Type: String

Length constraints: Minimum length of 1. Maximum length of 128.

Required: Yes

StreamName

The name of the stream for the merge.

Type: String

Length constraints: Minimum length of 1. Maximum length of 128.

Required: Yes

Response Elements

If the action is successful, the service sends back an HTTP 200 response with an empty HTTP body.

Errors

For information about the errors that are common to all actions, see Common Errors.

InvalidArgumentException

A specified parameter exceeds its restrictions, is not supported, or can't be used. For more information, see the returned message.

HTTP Status Code: 400

LimitExceededException

The requested resource exceeds the maximum number allowed, or the number of concurrent stream requests exceeds the maximum number allowed (5).

HTTP Status Code: 400

ResourceInUseException

The resource is not available for this operation. For example, you attempted to split a shard but the stream is not in the ACTIVE state.

HTTP Status Code: 400

ResourceNotFoundException

The requested resource could not be found. It might not be specified correctly, or it might not be in the ACTIVE state.

HTTP Status Code: 400

Examples

To merge two adjacent shards

The following example merges two adjacent shards.

Sample Request

POST / HTTP/1.1
Host: kinesis.<region>.<domain>
x-amz-Date: <Date>
Authorization: AWS4-HMAC-SHA256 Credential=<Credential>, SignedHeaders=content-type;date;host;user-agent;x-amz-date;x-amz-target;x-amzn-requestid, Signature=<Signature>
User-Agent: <UserAgentString>
Content-Type: application/x-amz-json-1.1
Content-Length: <PayloadSizeBytes>
Connection: Keep-Alive
X-Amz-Target: Kinesis_20131202.MergeShards
{
  "StreamName": "exampleStreamName",
  "ShardToMerge": "shardId-000000000000",
  "AdjacentShardToMerge": "shardId-000000000001"
}

Sample Response

HTTP/1.1 200 OK
x-amzn-RequestId: <RequestId>
Content-Type: application/x-amz-json-1.1
Content-Length: <PayloadSizeBytes>
Date: <Date>