Redis should be said to be one of the most popular NoSQL databases at present. Redis is usually used as a caching component to cache data. However, in addition to caching data, Redis can actually do many things.
Here are a few examples for your reference. Recommended: "redis video tutorial"
1. Latest list
For example, the latest news list on the news list page, if the total number is large In this case, try not to use select a from A limit 10, try the LPUSH command of redis to build a List, and just insert them one by one in order. But what if the memory is cleared? It’s also simple. If you can’t query the storage key, just use mysql to query and initialize a List into redis.
2. Ranking application
The redis data type mainly used to implement this function is the redis ordered set zset. zset is an extension of the set type. It has one more sequence attribute than the original type. This attribute will automatically adjust the sequence value every time data is inserted to ensure that the value values are continuously arranged in a certain order.
We assume that it is a game experience value ranking list. The main implementation idea is:
1. When a new player participates in the game, add a new value to the zset in redis A record (the record content depends on the specific requirements) has a score of 0
2. When the player's experience value changes, modify the player's score value
3. Use the ZREVRANGE method of redis to obtain it. Ranking
3. Counter application
Redis commands are all atomic. You can easily use INCR and DECR commands to perform atomic operations to build counts. system. Due to the single thread, concurrency issues can be avoided, error-free guaranteed, and 100% millisecond-level performance.
For example, in a web application, if you want to know the number of user clicks every day for a year, then you only need to use the user ID and related date information as keys, and execute it every time the user clicks on the page. One auto-increment operation is enough.
4. Data deduplication
Redis set can automatically deduplicate data. When you need to store a list of data and do not want duplicate data to appear, set is A good choice, and set provides an important interface for determining whether a member is in a set collection.
Implementation plan:
The internal implementation of set is a HashMap whose value is always null. In fact, it is quickly sorted by calculating hash. This is also what set can provide to determine whether a member is Reason within the set.
5. Real-time anti-spam system
Anti-spam systems are usually based on keywords. Redis is used to store related words, which can take advantage of the high performance of Redis. The monitoring system provides stable and accurate real-time monitoring functions. Typical cases include email systems, comment systems, etc.
6. Real-time messaging system that can publish and subscribe
The Pub/Sub system in Redis can build a real-time messaging system. For example, many are built using Pub/Sub Live chat application.
Design idea:
The server sends a message (including title, content), the title is stored in redis according to certain rules, and at the same time the title (with the minimum amount of information) is pushed to the client, and the customer clicks When reading the title, get the corresponding content to read.
If not read, you can prompt how many unread items, redis can quickly count
Clear the cache according to a certain period of time
Technical implementation:
Requires redis database, client websocket, server side websocket
7, queue application
Queue is widely used in current programs , such as log pushing, task processing, etc. In the past, http sqs was usually used to implement queues. In fact, queues can also be implemented using the list type of redis.
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The core function of Redis is a high-performance in-memory data storage and processing system. 1) High-speed data access: Redis stores data in memory and provides microsecond-level read and write speed. 2) Rich data structure: supports strings, lists, collections, etc., and adapts to a variety of application scenarios. 3) Persistence: Persist data to disk through RDB and AOF. 4) Publish subscription: Can be used in message queues or real-time communication systems.

Redis supports a variety of data structures, including: 1. String, suitable for storing single-value data; 2. List, suitable for queues and stacks; 3. Set, used for storing non-duplicate data; 4. Ordered Set, suitable for ranking lists and priority queues; 5. Hash table, suitable for storing object or structured data.

Redis counter is a mechanism that uses Redis key-value pair storage to implement counting operations, including the following steps: creating counter keys, increasing counts, decreasing counts, resetting counts, and obtaining counts. The advantages of Redis counters include fast speed, high concurrency, durability and simplicity and ease of use. It can be used in scenarios such as user access counting, real-time metric tracking, game scores and rankings, and order processing counting.

Use the Redis command line tool (redis-cli) to manage and operate Redis through the following steps: Connect to the server, specify the address and port. Send commands to the server using the command name and parameters. Use the HELP command to view help information for a specific command. Use the QUIT command to exit the command line tool.

Redis cluster mode deploys Redis instances to multiple servers through sharding, improving scalability and availability. The construction steps are as follows: Create odd Redis instances with different ports; Create 3 sentinel instances, monitor Redis instances and failover; configure sentinel configuration files, add monitoring Redis instance information and failover settings; configure Redis instance configuration files, enable cluster mode and specify the cluster information file path; create nodes.conf file, containing information of each Redis instance; start the cluster, execute the create command to create a cluster and specify the number of replicas; log in to the cluster to execute the CLUSTER INFO command to verify the cluster status; make

To read a queue from Redis, you need to get the queue name, read the elements using the LPOP command, and process the empty queue. The specific steps are as follows: Get the queue name: name it with the prefix of "queue:" such as "queue:my-queue". Use the LPOP command: Eject the element from the head of the queue and return its value, such as LPOP queue:my-queue. Processing empty queues: If the queue is empty, LPOP returns nil, and you can check whether the queue exists before reading the element.

Use of zset in Redis cluster: zset is an ordered collection that associates elements with scores. Sharding strategy: a. Hash sharding: Distribute the hash value according to the zset key. b. Range sharding: divide into ranges according to element scores, and assign each range to different nodes. Read and write operations: a. Read operations: If the zset key belongs to the shard of the current node, it will be processed locally; otherwise, it will be routed to the corresponding shard. b. Write operation: Always routed to shards holding the zset key.

How to clear Redis data: Use the FLUSHALL command to clear all key values. Use the FLUSHDB command to clear the key value of the currently selected database. Use SELECT to switch databases, and then use FLUSHDB to clear multiple databases. Use the DEL command to delete a specific key. Use the redis-cli tool to clear the data.


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