Redshift Concurrency Scaling

Introduction

Amazon Redshift is a strong data warehouse that helps you analyze large amounts of data quickly. As data volumes grow and user demands increase, maintaining optimal query performance can become challenging. This is where Redshift Concurrency Scaling comes into play.

This article will cover the basics of Redshift Concurrency Scaling, including setup commands and parameters. We will also discuss how it helps distribute workloads for high-performance and high-availability applications.

What is Redshift Concurrency Scaling?

Redshift Concurrency Scaling adjusts cluster capacity for more read queries at once, making a big difference. It changes how many questions your group can handle at once, making sure responses are always quick and consistent.

How does it work? Redshift automatically provisions additional transient clusters when Concurrency Scaling is on. This happens every time the number of concurrent user queries exceeds the configured queue threshold. Temporary groups read queries that Redshift can only handle in the queue.

Your main group can continue working on other tasks without interruption. Once the queue size falls below the threshold, the system automatically terminates the transient clusters to optimize costs.

Setting Up Concurrency Scaling

To leverage the power of Redshift Concurrency Scaling, you need to enable it on your cluster. Here’s how:

1. Ensure your cluster is running with a ra3.16xlarge or higher node type.

2. Execute the following SQL command to enable Concurrency Scaling:

ALTER CLUSTER <your-cluster-name> SET CONCURRENCY SCALING ENABLED;

3. Configure the Concurrency Scaling mode using the SET command. There are two modes available:

– AUTO: Redshift automatically manages the number of transient clusters based on workload. This is the default mode.

– MANUAL: You specify the maximum number of transient clusters.

4. To set the mode, use the following command:

ALTER CLUSTER <your-cluster-name> SET CONCURRENCY SCALING MODE 'AUTO|MANUAL';

5. If using MANUAL mode, set the maximum number of transient clusters:

ALTER CLUSTER <your-cluster-name> SET CONCURRENCY SCALING MAX_CLUSTERS <number>;

Workload Distribution with Query Queues

Redshift Concurrency Scaling works hand-in-hand with query queues to efficiently distribute workloads across your cluster and transient clusters. Query queues allow you to prioritize and manage different types of queries based on their importance and resource requirements.

By default, Redshift has a single default queue. However, you can create additional queues to segregate and prioritize workloads. Here’s an example of creating a new query queue:

CREATE QUEUE reporting_queue
PRIORITY 5
QUERY_GROUP 'reporting';

In this example, we create a reporting queue with a priority of 5. We then link the reporting queue to a query group called ‘reporting’. Queries submitted to this queue will have higher priority than those in the default queue.

To route queries to specific queues, you can use the SET command:

SET query_group TO 'reporting';

This action sets the current session’s query group to ‘reporting’, and the system will route subsequent queries to the associated queue.

Concurrency Scaling Parameters for High Availability

When configuring Redshift Concurrency Scaling for high availability applications, there are several key parameters to consider:

1. max_concurrency_scaling_clusters: This parameter specifies the maximum number of transient clusters that can be provisioned. Set it based on your workload requirements and budget constraints.
2. concurrency_scaling_mode: As mentioned earlier, this parameter determines whether Concurrency Scaling is managed automatically or manually.
3. wlm_query_slot_count: This parameter sets the number of query slots (concurrent queries) per cluster. Adjust it based on your workload characteristics and available resources.
4. query_group: Use query groups to route queries to specific queues and prioritize critical workloads.

Here’s an example configuration for a high availability setup:

ALTER CLUSTER <your-cluster-name> SET CONCURRENCY SCALING MAX_CLUSTERS 5;
ALTER CLUSTER <your-cluster-name> SET CONCURRENCY SCALING MODE 'AUTO';
ALTER CLUSTER <your-cluster-name> SET wlm_query_slot_count 50;
CREATE QUEUE critical_queue
PRIORITY 10
QUERY_GROUP 'critical';
CREATE QUEUE reporting_queue
PRIORITY 5
QUERY_GROUP 'reporting';

In this example, we will have up to 5 temporary clusters. We will also turn on automatic Concurrency Scaling. Additionally, we will assign 50 query slots per cluster. We create two queues, critical_queue and reporting_queue, with different priorities to handle critical and reporting workloads separately.

Real-World Example

Let’s consider a real-world scenario where an e-commerce company uses Redshift for their data warehousing needs. During busy sales times, they get a lot of questions from different departments like sales, inventory, and customer analysis.

To handle this increased workload, they enable Redshift Concurrency Scaling with the following configuration:

ALTER CLUSTER ecommerce_cluster SET CONCURRENCY SCALING ENABLED;
ALTER CLUSTER ecommerce_cluster SET CONCURRENCY SCALING MODE 'AUTO';
ALTER CLUSTER ecommerce_cluster SET CONCURRENCY SCALING MAX_CLUSTERS 10;
CREATE QUEUE sales_analytics_queue
PRIORITY 8
QUERY_GROUP 'sales_analytics';
CREATE QUEUE inventory_queue
PRIORITY 6
QUERY_GROUP 'inventory';
CREATE QUEUE customer_segmentation_queue
PRIORITY 4
QUERY_GROUP 'customer_segmentation';

When too many queries are running at once, Redshift will create more temporary clusters to manage the workload. The queries are efficiently distributed across the main cluster and transient clusters based on their assigned query groups and queue priorities.

As a result, the e-commerce company maintains optimal query performance during peak periods, ensuring timely insights for critical business decisions. The sales analytics queries receive the highest priority, followed by inventory management and customer segmentation queries.

Conclusion

Redshift Concurrency Scaling allows you to adjust your cluster’s capacity to handle sudden increases in queries efficiently. By leveraging query queues and configuring resource allocation, you can efficiently distribute workloads and prioritize critical queries for high-performance, high-availability applications.

Remember to consider factors such as workload characteristics, resource availability, and budget when configuring Concurrency Scaling. With the right setup, you can unlock the full potential of Redshift and deliver lightning-fast query performance to your users.

For more information on Redshift Concurrency Scaling, refer to the official AWS documentation:

• Concurrency Scaling Guide
• Workload Management Guide

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