What are the Redis memory configuration parameters?

**The core parameter of Redis memory configuration is maxmemory, which limits the amount of memory that Redis can use. When this limit is exceeded, Redis executes an elimination strategy based on maxmemory-policy, including: noeviction (directly reject write), allkeys-lru/volatile-lru (eliminated by LRU), allkeys-random/volatile-random (eliminated by random elimination), and volatile-ttl (eliminated by expiration time). Other related parameters include maxmemory-samples (LRU sample quantity), rdb-compression

Redis memory configuration? This is a cliché, but often troublesome problem. Do you think that simply increasing maxmemory will make everything go well? Naive! This article will look at the Redis memory configuration, so that you no longer scratch your head for memory rush. After reading it, you can easily control Redis's memory configuration like an experienced driver, so that your Redis can run fast and steadily.

Don't rush to see the parameters first, let's talk about Redis's memory model first. Redis is a memory-based database where all data is stored in memory. This determines the importance of memory configuration. If the memory is insufficient, the performance will be degraded at the least, and the operation will be down. Only by understanding this can you better understand the role of various memory configuration parameters.

The core memory parameter of Redis is undoubtedly maxmemory . It limits the maximum amount of memory that Redis can use. If this limit is exceeded, Redis will execute different elimination strategies based on maxmemory-policy you set. There are many strategies, such as noeviction , allkeys-lru , allkeys-random , volatile-lru , volatile-random , volatile-ttl , each with its own characteristics. noeviction is the simplest and most crude, and it directly refuses to write new data, which can easily lead to application blockage; allkeys-lru and volatile-lru will eliminate the longest-lasting keys according to the LRU algorithm, which is relatively gentle; while the random strategy is more casual, suitable for scenarios with low requirements for data accuracy. Which strategy to choose depends on your application scenario. Don't use noeviction to save trouble, it's a time bomb.

In addition to maxmemory and maxmemory-policy , there are other memory-related parameters, such as maxmemory-samples that controls the number of samples of LRU algorithms, affecting the accuracy of the elimination strategy; rdb-compression controls the compression level of RDB persistent files, affecting disk space and persistence speed; and aof-rewrite-incremental-fsync affects memory usage during AOF rewrite, etc. The settings of these parameters need to be comprehensively considered based on your Redis version, hardware resources, and application characteristics.

Let’s take a look at an example and experience the differences between different strategies:

 <code class="python"># 模拟数据import random import time data = {f"key_{i}": f"value_{i}" for i in range(1000)} # 连接Redis (假设你已经安装了redis-py) import redis r = redis.Redis(host='localhost', port=6379, db=0) # 设置不同的maxmemory-policy policies = ["noeviction", "allkeys-lru", "volatile-lru"] for policy in policies: print(f"Testing policy: {policy}") r.config_set('maxmemory', '10mb') # 设置最大内存为10MB r.config_set('maxmemory-policy', policy) start_time = time.time() try: for key, value in data.items(): r.set(key, value) except redis.exceptions.RedisError as e: print(f"Error: {e}") end_time = time.time() print(f"Time taken: {end_time - start_time:.2f} seconds") print("-" * 20) r.flushall() # 清理数据</code>

This code simulates writing large amounts of data to Redis and tests three different maxmemory-policy . You will find that noeviction will directly report an error when there is insufficient memory, while the lru strategy will consume more time because data elimination is required. In practical applications, you need to choose the appropriate strategy based on your data characteristics and performance requirements.

Finally, let me remind you not to forget to monitor your Redis memory usage. You can use Redis's own monitoring tools or some third-party monitoring tools to discover problems in a timely manner and avoid accidents. Memory configuration is not a one-time thing, and needs to be continuously adjusted according to actual conditions. This requires accumulation of experience and continuous learning and practice. I wish you to play with Redis memory configuration!

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