Real-time collection of 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. The real-time key statistics feature allows you to view large keys and hotkeys in Tair instances in real time and query large keys and hotkeys that were generated within the previous four days. You can use the real-time key statistics feature to obtain key information, such as the number of elements and access frequency of keys, and optimize instances based on the key information.

Usage notes

The instance that you want to manage is a DRAM-based or persistent memory-optimized instance.

Definitions

Key type

Statistical ranking mechanism

Large keys

Keys that map to the String, List, Hash, Set, Zset, and Stream data structures are sorted and ranked based on the string length or number of elements contained in the keys. The standard threshold for a key to be considered large is set to a string length or an element count of 2,000.

For keys of the String type, the key size is determined based on the string length.
For keys of the List, Hash, Set, Zset, and Stream types, the key size is determined based on the number of elements.

For Tair instances, large keys of the following self-developed data structures are supported: TairString, TairHash, TairGIS, TairBloom, TairDoc, TairCpc, TairZset, TairRoaring, and TairTS.

Note

When specific keys reach the standard threshold, the three largest keys are displayed. If fewer than three keys reach the threshold, only the keys that reach the threshold are displayed. If two keys have the same number of elements or string length, the key that first reaches the number or length is assigned a higher rank. If the instance uses the cluster or read/write splitting architecture, the system displays the three largest keys of each data type in each data shard or read replica.
Keys that have not been accessed for a long period of time may not be included in the statistical ranking. You can use the offline key analysis feature to obtain information about large keys, such as the memory usage of keys, the distribution of keys, the memory usage and distribution of elements in keys, and the distribution of time-to-live (TTL) values across keys. For more information, see Use the offline key analysis feature.

Hotkeys

Tair uses efficient sorting and statistical algorithms based on the Least Recently Used (LRU) key eviction policy to identify hotkeys in an instance.

Note

Statistics of up to 50 hotkeys can be collected at the same time.
For Tair DRAM-based instances of version 5.0.50 and later, the following enhancements to hotkeys are made:
- A key is considered a hotkey if its queries per second (QPS) exceeds 5,000. In earlier versions, a key is considered a hotkey if its QPS exceeds 3,000.
- The exact QPS of a hotkey can be displayed. In earlier versions, the approximate QPS range can be displayed only if the QPS of a hotkey is less than 6,000.

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.
- On the History tab, you can query the historical large keys and hotkeys within the previous 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 period of time.
DescribeTopBigKeys	Queries the top 20 large keys over a period of time.
DescribeHotKeys	Queries the hotkeys of a Tair instance.