Automatic bandwidth adjustment - Redis| Alibaba Cloud Documentation Center

Database Autonomy Service (DAS) provides a feature to automatically scale the bandwidth of an ApsaraDB for Redis instance. DAS can detect the average bandwidth usage in real time to help you handle expected or unexpected traffic spikes so that you can focus on improving your business. This topic describes how to enable automatic bandwidth adjustment for an ApsaraDB for Redis instance.

Prerequisites

The instance is an instance of the ApsaraDB for Redis Community Edition or a performance-enhanced or hybrid-storage instance of the ApsaraDB for Redis Enhanced Edition (Tair). For more information about performance-enhanced instances and hybrid-storage instances, see Performance-enhanced instances and Hybrid-storage instances (phased out).
The ApsaraDB for Redis instance is a standard instance.

Note Read/write splitting instances and cluster instances allow you to manually adjust the maximum bandwidth value. For more information, see Adjust the bandwidth of an ApsaraDB for Redis instance.
A Resource Access Management (RAM) role that is linked to DAS is created to enable automatic bandwidth adjustment. For more information, see AliyunServiceRoleForDAS role.

Note If you have not created a RAM role that is linked to DAS, DAS can automatically create a service-linked role when you enable automatic bandwidth adjustment.

Background information

The bandwidth of an instance varies based on the instance type. If the bandwidth in use reaches the allocated bandwidth, network congestion may occur and the performance of the instance may deteriorate. When your instance needs to process data during peak hours or a large number of large key reads and writes occur in your business, you must increase the bandwidth limit to prevent your business from being affected. A bandwidth adjustment helps you increase bandwidth at a lower cost and higher speed than an instance type change. A bandwidth adjustment immediately takes effect and does not cause transient connections. For more information about how to adjust the bandwidth, see Manually adjust the bandwidth of an ApsaraDB for Redis instance.

Scenarios

The bandwidth of an instance varies based on the instance type. If the bandwidth in use reaches the allocated bandwidth, network congestion may occur and instance performance may deteriorate. To prevent these situations, you can enable the bandwidth auto scaling feature. A bandwidth adjustment helps you increase bandwidth at a lower cost than an instance specification change and can help prevent transient connections.


Scenario	Description
Handle traffic spikes	You can adjust the bandwidth of the instance to handle traffic spikes during promotional events such as a flash sale. After these events end, you can decrease the bandwidth of the instance to reduce costs.
Mitigate impacts on your business	If a large number of read and write operations are performed on large keys within a short period of time, you must temporarily increase the bandwidth of the instance to mitigate impacts on your business and to reserve time to process these operations.
Deal with skewed requests at low costs	If your instance is in the cluster or read/write splitting architecture, some data shards or read replicas of the instance are more frequently accessed than others. For more information about the cluster and read/write splitting architecture, see Cluster master-replica instances and Read/write splitting instances. As a result, the bandwidth consumption of these data shards or read replicas frequently reaches the allocated bandwidths. However, the usage of the bandwidths that are allocated to other data shards or read replicas is low. After you enable the bandwidth auto scaling feature, the system identifies the data shards or read replicas whose allocated bandwidth is insufficient and increases the bandwidth for them. You do not need to manually increase the bandwidth or change the specifications of the instance to which these data shards or read replicas belong. This reduces costs and facilitates O&M.

Process

After you enable the bandwidth auto scaling feature, the system performs the following operations based on the auto scaling policy and observation window that you configure. The increment or decrement is calculated by the system.

If the bandwidth increase threshold of an instance is reached, the system increases the bandwidth and continues to monitor bandwidth usage. If the threshold is reached again, the system increases the bandwidth again. The bandwidth can be increased up to three times the default bandwidth of the instance type. If you want to increase this bandwidth limit, you can upgrade the specifications of your instance and then adjust the bandwidth.
If the bandwidth decrease threshold of an instance is reached, the system decreases the bandwidth and continues to monitor bandwidth usage. If the threshold is reached again, the system decreases the bandwidth again. The bandwidth can be decreased to the default bandwidth of the instance type.

Note

If your instance is in the cluster or read/write splitting architecture, the system monitors the bandwidth usage of data shards and read replicas and increases the bandwidth only for the data shards or read replicas whose allocated bandwidth is insufficient.
If you enable the subscription service, you are notified of every increase or decrease by the notification method that you select, such as an email. For more information about how to enable the subscription service, see the relevant section in this topic.
To ensure that DAS can access resources of your ApsaraDB for Redis instance, the system authorizes DAS to use the AliyunServiceRoleForDAS role after you enable this feature.

Limits

The bandwidth of an instance can be increased to up to three times the bandwidth that is provided for the instance type. If you require higher bandwidth for an instance, you can change the specifications of the instance or upgrade the instance from a standard instance to a cluster instance. Then, you can increase the bandwidth of the instance. If the increased bandwidth is still insufficient, submit a ticket.

Note For more information about the bandwidths that are supported by different instance types, see Overview.

If you perform the following operations on an instance, the extra bandwidth that you purchased becomes invalid and you receive a refund. You must re-adjust the instance bandwidth based on your business requirements. By default, the adjusted bandwidth inherits the expiration time of the previously purchased extra bandwidth.


Operation	Exception
Upgrade the major version	None
Change the configurations of an instance	If the instance is a standard instance, the bandwidth settings remain valid after you change the specifications of the instance.
Migrate an instance across zones	If the instance is a standard instance, the bandwidth settings remain valid.

Billing

You are charged per day based on the amount and usage duration of the extra bandwidth that you purchase. The fees vary based on the region that you select. For more information, see Billable items and prices.

Note You are not charged for the default bandwidth that is provided for the instance type. You are charged only for the extra bandwidth that you purchase.

Procedure

Log on to the DAS console.
In the left-side navigation pane, click Instance Monitoring. On the Instance Monitoring page, click the Redis tab.
On the Redis tab, find the instance that you want to manage and click the instance ID. The instance details page appears.
In the left-side navigation pane of the instance details page, click Autonomy Center. In the upper-right corner of the page that appears, click Autonomy Service Settings.

On the Autonomous Function Settings tab of the Autonomous Function Management panel, enable the autonomy service and complete Automatic Bandwidth Upgrade and Automatic Bandwidth Downgrade settings. Then, click the Event Subscription Settings tab. On the Event Subscription Settings tab, enable the subscription service and complete event subscription settings.

On the Optimization and Throttling tab, select Automatic Bandwidth Upgrade and Automatic Bandwidth Downgrade.


Category	Parameter	Description
Automatic Bandwidth Upgrade	Automatic Bandwidth Upgrade	Select Automatic Bandwidth Upgrade to enable this feature.
	Average Bandwidth Usage	If the value of Average Bandwidth Usage is greater than or equal to the threshold value that you specify for this parameter, automatic bandwidth upgrade is triggered. Unit: %. Compare the average inbound bandwidth usage and the average outbound bandwidth usage. Then, set Average Bandwidth Usage to the greater value.
	Observation Window	Select the length of the observation window. Unit: minutes. Note In this example, 30 minutes is selected. During this observation window, if the value of Average Bandwidth Usage is greater than or equal to 70%, the maximum bandwidth of the instance is increased. The maximum bandwidth can be increased up to three times the maximum bandwidth that is provided for the current instance type. If the value of Average Bandwidth Usage is less than or equal to 30%, the maximum bandwidth is decreased. The lowest bandwidth that you can specify is the default bandwidth of the instance.
Automatic Bandwidth Downgrade	Automatic Bandwidth Downgrade	Select Automatic Bandwidth Downgrade to enable this feature. You must select Automatic Bandwidth Upgrade before you can select Automatic Bandwidth Downgrade.
Automatic Bandwidth Downgrade	Average Bandwidth Usage	If the value of Average Bandwidth Usage is less than or equal to the threshold value that you specify for this parameter, automatic bandwidth downgrade is triggered. Unit: %. Compare the average inbound bandwidth usage and the average outbound bandwidth usage. Then, set Average Bandwidth Usage to the smaller value.

Click the Event Subscription Settings tab. On the Event Subscription Settings tab, configure the parameters as prompted.


Parameter	Description
Enable Subscription Service	Turn on the switch to enable the feature. If an event of the specified level or a higher level occurs, DAS uses the specified method such as an email to keep you updated. This ensures that you are notified when events occur on your instance.
Urgency	Select the lowest level of events for which DAS sends notifications. If an event of the specified level or a higher level occurs, DAS sends a notification. Valid values: Critical: events that affect the running of the databases. Warning: events that may affect the running of the databases. Optimize: events for which optimization suggestions are generated based on the status of the databases. Notification: basic events and events related to performance snapshots. Note To subscribe to automatic scale-up events and scale-down suggestions, select the Notification or Optimize level.
Select Contacts/Contact Groups	Select contacts or contact groups in the Existing Contacts/Contact Groups section and click the > icon to move them to the Selected Contacts/Contact Groups section.
Notification Method	Select a notification method. You can select one or more methods. We recommend that you select at least SMS to ensure timeliness.
Notification Language	Select a notification language. Valid values: Chinese and English.
Minimum Notification Interval	Select the minimum interval between two notifications about the same event. For example, you can set the interval to 5 minutes. In this case, if the event occurs again after you first receive a notification for the event, you are notified again 5 minutes later.

Click OK.