:Development and O&M standards for Tair

Resource type

Description

Computing resources

Wildcard characters, concurrent Lua scripts, one-to-many Pub/Sub models, and hotkeys consume a large amount of computing resources. For cluster instances, these items can also cause skewed requests and underutilization of data shards.

Storage resources

Streaming jobs and large keys consume a large amount of storage resources. For cluster instances, these items can also cause data skew and underutilization of data shards.

Network resources

Database-wide scans (by running the KEYS command) and range queries of large keys and values (by running the HGETALL command) consume a large amount of network resources and often cause thread congestion.

Importance

Standard

Description

★★★★★

• High-speed cache: We recommend that you disable append-only file (AOF) persistence in cache-only scenarios to reduce overheads and prevent strong dependence on the data in the cache because the data may be evicted. For more information, see Disable AOF persistence. For example, after a Tair database is full, a data eviction policy is triggered to make space for new data to be written. Depending on the write workload of your business, this can result in increased latency.

  Important

  To use the data flashback feature, you must enable AOF. For more information, see Use data flashback to restore data by point in time.

• In-memory databases: We recommend that you choose Tair persistent memory-optimized instances that offer command-level persistence. In addition, you can monitor memory usage by configuring alerts in the databases. For more information, see Alerting settings.

★★★★★

Deploy your business close to Tair instances. For example, you can deploy your business in an Elastic Compute Service (ECS) instance that resides in the same virtual private cloud (VPC) as your Tair instances.

Tair is a high-performance database service. However, if you deploy your business server far from Tair instances and the business server is connected to the instances over the Internet, the performance of Tair is greatly compromised due to network latency.

★★★★☆

Create a Tair instance for each service.

Do not use a Tair instance for different services. For example, do not use a Tair instance for both high-speed caching and in-memory database services. Otherwise, the eviction policies, slow queries, and FLUSHDB command execution of one service affect other services.

★★★★☆

Configure appropriate eviction policies to evict expired keys.

The default eviction policy for expired keys in Tair is volatile-lru For more information about eviction policies, see Parameters that can be configured for Tair.

★★★☆☆

Manage stress testing data and duration.

Tair does not delete stress testing data. To prevent impacts on your business, you must manage stress testing data and duration by yourself.

Importance

Standard

Description

★★★★★

Set key values to an appropriate size. We recommend that you keep the size of values stored in keys below 10 KB.

Excessively large values can cause data skew, hotkeys, high bandwidth, or high CPU utilization. You can prevent these issues from the beginning by making sure that key values are of proper size.

★★★★★

Configure proper key names that have proper length.

• Key names:

  • Use readable strings as key names. If you want to combine a database name, table name, and field name into a key name, we recommend that you use colons (:) to separate them. Example: project:user:001.

  • Shorten key names without compromising their ability to describe your business. For example, username can be shortened to u.

  • In Tair, braces {} are recognized as hash tags. In this case, if you use cluster instances, you must correctly use braces in key names to prevent data skew. For more information, see Redis cluster specification.

    Note

    For a cluster instance, if you want to manage multiple keys by running a command such as the RENAME command and do not use hash tags to ensure that the keys reside in the same data shard, the command cannot be run.

• Length: We recommend that you keep key names within 128 bytes and preferably shorter.

★★★★★

For complex data structures that support sub-keys, you must avoid including excessive sub-keys in one key. We recommend that you include less than 1,000 sub-keys in a key.

The time complexity of some commands, such as HGETALL, is directly related to the number of sub-keys. Excessive sub-keys increase the time complexity of a command. If you frequently run commands whose time complexity is O(N) or higher, issues such as slow queries, data skew, and hotkeys occur.

★★★★☆

Use the serialization method to convert values into readable structures.

The bytecode of a programming language may change when the version of the language changes. If you store naked objects (such as Java objects and C# objects) in Tair instances, the software stack may be difficult to upgrade. We recommend that you use the serialization method to convert values into readable structures.

Importance

Standard

Description

★★★★★

Use JedisPool or JedisCluster to connect to Tair instances.

If you use a single connection, the client cannot automatically reconnect to Tair instances after the connection times out. For more information about how to use JedisPool to connect to Tair instances, see Use a client to connect to a Tair instance, JedisPool optimization, and JedisCluster.

★★★★☆

Design proper fault tolerance mechanisms for your clients.

Network fluctuations and high usage of resources may cause connection timeouts or slow queries. To prevent these risks, you must design proper fault tolerance mechanisms for your clients.

★★★★☆

Set longer retry intervals for your clients.

If retry intervals are shorter than required, such as shorter than 200 milliseconds, a large number of retries may occur in a short period of time. This can result in a service avalanche. For more information, see Retry mechanisms for Tair clients.

Importance

Standard

Description

★★★★★

Avoid range queries, such as those executed by running the KEYS * command. Instead, use multiple point queries or run the SCAN command to reduce latency.

Range queries may cause service interruptions, slow queries, or congestion.

★★★★★

Use extended data structures to perform complex operations. For more information, see Extended data structures of Tair. Do not use Lua scripts.

Lua scripts consume a large amount of computing and memory resources and do not support multi-threading acceleration. Overly complex or improper Lua scripts may result in the exhaustion of resources.

★★★★☆

Use pipelines to reduce the round-trip time (RTT) of data.

If you want to send multiple commands to a server and your client does not depend on each response from the server, you can use a pipeline to send the commands at a time. When you use pipelines, take note of the following items:

• A client that uses pipelines exclusively connects to a server. We recommend that you establish a dedicated connection for pipeline operations to separate them from regular operations.

• Each pipeline must contain a proper number of commands. We recommend that you use each pipeline to send no more than 100 commands.

★★★★☆

Use transaction commands. For more information, see Limits on commands supported by Tair.

When you use transaction commands, take note of the following limits:

• Unlike transactions in relational databases, transactions in Tair cannot be rolled back.

• If you want to run transaction commands on cluster instances, use hash tags to ensure that the keys to be managed are allocated in the same hash slot. You must also prevent skewed storage that hash tags may cause.

• Do not encapsulate transaction commands in Lua scripts, because the compilation and loading of these commands consume a large amount of computing resources.

★★★★☆

Do not use the Pub/Sub command group to perform a large number of message distribution tasks. For more information, see Limits on commands supported by Tair.

The Pub/Sub command group does not support data persistence or acknowledge mechanisms that ensure data reliability. We recommend that you do not use Pub or Sub commands to perform a large number of message distribution tasks. For example, if you use these commands to distribute a message whose size is greater than 1 KB to more than 100 subscriber clients, server resources may be exhausted and subscriber clients may not receive the message.

Importance

Standard

Description

★★★★★

Understand the impacts of different instance management operations.

Configuration changes or restarts affect the status of a Tair instance. For example, transient connections may occur on the instance. Before you perform the preceding operations, make sure that you understand the impacts. For more information, see Instance states and impacts.

★★★★★

Verify the error handling capabilities or disaster recovery logic of a client.

Tair can monitor the health status of nodes. If a master node in an instance becomes unavailable, Tair automatically triggers a master-replica switchover. The roles of master and replica nodes are switched over to ensure the high availability of the instance. Before a client is generally available, we recommend that you manually trigger the master-replica switchover. This can help you verify the error handling capabilities or disaster recovery logic of the client. For more information, see Manually switch workloads from a master node to a replica node.

★★★★★

Disable time-consuming or high-risk commands.

In a production environment, abuse of commands may cause problems. For example, the FLUSHALL command can delete all data. The KEYS command may cause network congestion. To improve the stability and efficiency of services, you can disable these commands to minimize risks. For more information, see Disable high-risk commands.

★★★★☆

Handle pending events at the earliest opportunity.

To enhance user experience and provide improved service performance and stability, Alibaba Cloud occasionally generates pending events to upgrade the hardware and software of specific servers or replace network facilities. For example, a pending event is generated when the minor version of databases needs to be updated. After you receive an event notification from Alibaba Cloud, you can check the impacts of the event and change the scheduled time of the event to meet your business requirements. For more information, see View and manage pending events.

★★★★☆

Configure alerts for core metrics to better monitor the status of your instances.

Configure alerts for core metrics such as CPU utilization, memory usage, and bandwidth usage to monitor the status of your instances in real time. For more information, see Alerting settings.

★★★★☆

Use O&M features provided by Tair to check the status of instances or troubleshoot resource usage exceptions on a regular basis.

• Use slow logs to troubleshoot timeout issues: Slow logs help you locate slow queries and the IP addresses of the clients that send the query requests. Slow logs provide a reliable basis for addressing timeout issues.

• View the performance monitoring data: Tair supports a variety of performance metrics. These metrics allow you to gain insights into the status of Tair instances and troubleshoot issues at the earliest opportunity.

• Create a diagnostic report: Diagnostic reports help you evaluate the status of Tair instances, such as performance level, skewed requests, and slow logs. Diagnostic reports also help you identify exceptions on Tair instances.

• Offline key analysis: You can use the offline key analysis feature to identify large keys in Tair instances. You can also learn about the memory usage, distribution, and TTL of large keys.

• Use the real-time key statistics feature: The real-time key statistics feature helps you identify hotkeys in Tair instances and allows you to further optimize your databases.

★★★☆☆

Enable the audit log feature and evaluate audit logs.

After you enable the audit log feature, the audit statistics about write operations are recorded. Tair also allows you to query, analyze, and export audit logs. These features help you monitor the security and performance of your Tair instances. For more information, see Enable the audit log feature.