real-time key statistics and related API operations - Tair

Tair integrates the key analysis feature of Database Autonomy Service (DAS) to provide the real-time key statistics feature. This feature allows you to view large keys and hotkeys in instances in real time. It also allows you to query large keys and hotkeys that were generated within the last four days. You can use this feature to obtain key information, such as the number of elements and access frequency of keys, and optimize instances based on the information.

Usage notes

The instance that you want to manage is an Enhanced Edition (Tair) DRAM-based instance.

Definitions

Key type	Definition
Large key	Tair sorts list, hash, set, and zset keys based on the number of elements in these keys. Tair considers the top three keys that have the most elements as large keys. If two keys have the same number of elements, the key that first reaches this number ranks higher. Note For a cluster instance or a read/write splitting instance, the system displays the top three largest keys in each data shard or read replica. You can use the cache analysis feature to obtain more information about large keys, such as the memory usage and distribution of keys, the memory usage and distribution of elements in keys, and the expiration time of keys. For more information, see Use the offline key analysis feature.
Hotkey	Tair uses the Least Recently Used (LRU) cache eviction policy and efficient sorting and statistical algorithms to identify hotkeys in an instance. Note Tair allows you to query up to 50 hotkeys at a time. In most cases, if the number of queries sent to a key per second is more than 3,000, the key is considered a hotkey.

Procedure

Log on to the Tair console and go to the Instances page. In the top navigation bar, select the region in which the instance that you want to manage resides. Then, find the instance and click the instance ID.
In the left-side navigation pane, choose CloudDBA > Real-time Key Statistics.
Click the Real-time tab to view real-time data or click the History tab to view historical data based on your business requirements.
Figure 1. Key analysis
Note
- If the instance is a cluster instance or a read/write splitting instance, you can select a node from the Current Node drop-down list.
- If the queries per second (QPS) of a key reaches 6,000, the system stops calculating the accurate QPS of the key. In this case, >=6000 is displayed for such a hotkey in the Access Frequency column.
- On the History tab, you can query the historical large keys and hotkeys within the last four days. The time range to query cannot exceed 3 hours. For example, if the current time is 16:00 on July 15, 2021, you can query the large keys and hotkeys from 16:00 on July 11 to 16:00 on July 15. If you set the beginning of the time range to query to 16:00 on July 11, the end of the time range to query cannot be later than 19:00 on July 11.

Related API operations

DAS API operation	Description
DescribeHotBigKeys	Queries the hotkeys and large keys in the memory in real time.
DescribeTopHotKeys	Queries the top 20 hotkeys over a specified period of time.
DescribeTopBigKeys	Queries the top 20 large keys over a specified period of time.
DescribeHotKeys	Queries the hotkeys of a Tair instance.