Redis fully utilized in 11 web application scenarios

Listed below are 11 Web application scenarios, in which the features of Redis can be fully utilized to greatly improve efficiency.

1. Display the latest project list on the home page.

Redis uses a resident memory cache, which is very fast. LPUSH is used to insert a content ID, which is stored as a key at the head of the list. LTRIM is used to limit the number of items in the list to a maximum of 5000. If the amount of data the user needs to retrieve exceeds this cache capacity, then the request needs to be sent to the database.

2. Delete and filter.

If an article is deleted, you can use LREM to completely clear it from the cache.

3． Rankings and related issues.

The leader board is sorted by score. The ZADD command can directly implement this function, while the ZREVRANGE command can be used to obtain the top 100 users according to their scores. ZRANK can be used to obtain user rankings, which is very direct and easy to operate.

4. Sorted by user votes and time.

This is like a Reddit leaderboard, with scores changing over time. Use the LPUSH and LTRIM commands together to add articles to a list. A background task is used to obtain the list and recalculate the order of the list, and the ZADD command is used to populate the generated list in the new order. Lists enable very fast retrieval, even for heavily loaded sites.

5． Processing of expired items.

Use unix time as a keyword to keep the list sorted by time. Retrieve current_time and time_to_live to complete the difficult task of finding expired items. Another background task uses ZRANGE...WITHSCORES to query and delete expired entries.

6． count.

The use of various data statistics is very wide, such as wanting to know when an IP address is blocked. The INCRBY command makes this easy, keeping count by atomic increment; GETSET is used to reset the counter; and the expiration attribute is used to confirm when a keyword should be deleted.

7． A specific project within a specific time.

This is a visitor-specific problem and can be solved by using the SADD command for each page view. SADD does not add already existing members to a collection.

8. Real-time analysis of what is happening, used for data statistics and spam prevention, etc.

Using Redis primitive commands, it is easier to implement a spam filtering system or other real-time tracking system.

9. Pub/Sub.

Maintaining user mappings of data across updates is a common task in systems. Redis's pub/sub functionality makes this easier using the SUBSCRIBE, UNSUBSCRIBE, and PUBLISH commands.

10. queue.

Queues can be seen everywhere in current programming. In addition to push and pop type commands, Redis also has blocking queue commands, which allow a program to be added to the queue by another program during execution. You could also do something more interesting, like a rotating queue of updated RSS feeds.

11. cache.

Redis cache is used in the same way as memcache.

Network applications cannot engage in endless model wars. Look at these Redis primitive commands. Although they are simple but powerful, what can be accomplished by combining them is even more unimaginable. Of course, you can write specialized code to do all of these operations, but Redis is obviously easier to implement.

There is no doubt that Redis has created a new way of data storage. Using Redis, we don’t have to focus on how to put the elephant in the refrigerator when facing a database with monotonous functions. Instead, we use Redis’s flexible data structures and data operations to build different refrigerators for different elephants. Hope you like this metaphor.

The following is a fresh article written by @antirez, the author of Redis. He describes some application scenarios that Redis is more suitable for. NoSQLFan briefly lists them here for everyone to have an overview:

1. The operation of fetching the latest N data

For example, typically fetching the latest articles on your website, through the following method, we can put the IDs of the latest 5000 comments in Redis's List collection, and obtain the excess portion from the database

• Use the LPUSH latest.commentseddfa97ffc1dc71769e3f42e462dfe8e command to insert data into the list collection

• After the insertion is completed, use the LTRIM latest.comments 0 5000 command to always save only the latest 5000 IDs

• Then we get a certain ID on the client When commenting on a page, you can use the following logic (pseudocode)

FUNCTION get_latest_comments(start,num_items):
    id_list = redis.lrange("latest.comments",start,start+num_items-1)
    IF id_list.length < num_items
        id_list = SQL_DB("SELECT ... ORDER BY time LIMIT ...")
    END
    RETURN id_list
END

If you have different filtering dimensions, such as the latest N items in a certain category, then you can create another button If this category of List only stores IDs, Redis is very efficient.

2. Ranking application, take TOP N operations

The difference between this requirement and the above requirement is that the previous operation uses time as the weight, and this one is based on a certain condition. Weight, such as sorting by the number of likes, then our sorted set is needed. Set the value you want to sort to the score of the sorted set, and set the specific data to the corresponding value. Each time You only need to execute one ZADD command at a time.

3. Applications that need to accurately set the expiration time

For example, you can set the score value of the sorted set mentioned above to the timestamp of the expiration time, then You can simply sort by the expiration time and clear the expired data regularly. Not only does it clear the expired data in Redis, you can completely regard the expiration time in Redis as an index of the data in the database, and use Redis to find out which data is needed. Expired deletion, and then accurately delete the corresponding records from the database.

4.Counter application

Redis commands are all atomic. You can easily use INCR and DECR commands to build a counter system.

5.Uniq operation to obtain all data deduplication values ​​for a certain period of time

This is the most suitable to use the set data structure of Redis. You only need to keep throwing data into the set. set means collection, so it will be automatically sorted.

6. Real-time system, anti-spam system

Through the set function mentioned above, you can know whether an end user has performed a certain operation, and you can find its Collection of operations and analysis, statistical comparison, etc. Nothing is impossible, only unimaginable.

7. Pub/Sub builds a real-time messaging system

Redis’ Pub/Sub system can build a real-time messaging system, such as many examples of real-time chat systems built with Pub/Sub.

8. Build a queue system

Use list to build a queue system, use sorted set to even build a priority queue system.

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