How to get all fields and values from a hash using HGETALL?

To ensure Redis security, you need to configure from multiple aspects: 1. Restrict access sources, modify bind to specific IPs or combine firewall settings; 2. Enable password authentication, set strong passwords through requirepass and manage properly; 3. Close dangerous commands, use rename-command to disable high-risk operations such as FLUSHALL, CONFIG, etc.; 4. Enable TLS encrypted communication, suitable for high-security needs scenarios; 5. Regularly update the version and monitor logs to detect abnormalities and fix vulnerabilities in a timely manner. These measures jointly build the security line of Redis instances.

Redis master-slave replication achieves data consistency through full synchronization and incremental synchronization. During the first connection, the slave node sends a PSYNC command, the master node generates an RDB file and sends it, and then sends the write command in the cache to complete the initialization; subsequently, incremental synchronization is performed by copying the backlog buffer to reduce resource consumption. Its common uses include read and write separation, failover preparation and data backup analysis. Notes include: ensuring network stability, reasonably configuring timeout parameters, enabling the min-slaves-to-write option according to needs, and combining Sentinel or Cluster to achieve high availability.

PSYNC is a partial resynchronization mechanism in Redis master-slave replication, which is used to synchronize only data lost during disconnection after the slave server is disconnected to improve synchronization efficiency. Its core relies on the ReplicationBacklog, which is a queue maintained by the main server. The default size is 1MB and saves the most recently executed write commands. When the slave server reconnects, a PSYNC command will be sent, and the master server will determine whether partial synchronization can be performed based on this: 1. The runid must be consistent; 2. Offset must be in the backlog buffer. If the condition is satisfied, data will continue to be sent from the offset, otherwise full synchronization will be triggered. Methods to improve the success rate of PSYNC include: 1. Appropriately increase repl-b

To reduce Redis memory usage, it is necessary to optimize the data structure, compress the data, set the expiration time reasonably, and avoid redundant keys. First, using efficient data structures such as Hash, Ziplist and Intset can save space; second, compress large strings or JSON data before storage to reduce volume; third, set appropriate expiration time for keys and enable elimination strategies; fourth, avoid duplicate or unnecessary keys and check large keys regularly. These methods can effectively reduce memory usage.

RedisClusterhandlesmasternodefailurethroughautomaticdetection,replicapromotion,andclientredirection.1.Nodesdetectfailureviagossipprotocol,markingnodeasPFAILthenFAILifmajorityofmastersagree.2.Eligiblereplicasrequestvotes,andthewinnerbecomesnewmaster,t

To get a list of members based on scores from a ordered set of Redis, the ZRANGEBYSCORE command should be used. 1) The basic syntax is ZRANGEBYSCOREkeyminmax, which is used to obtain members within the specified score range; 2) Pagination query can be implemented by adding LIMIToffsetcount; 3) The boundary value can be excluded by adding (symbols before min or max; 4) The WITHSCORES flag can be added to return members and their scores at the same time.

Synchronous replication is copied to the standby system in real time every time it is written to the main system, ensuring zero data loss but affecting performance; asynchronous replication confirms the write first and then delays the replication, which has good performance but may lose data. Select synchronous replication to be suitable for critical systems such as finance, high availability clusters, and scenarios where data loss cannot be tolerated; select asynchronous replication to be suitable for distributed applications with data warehouses, backup systems and high-performance requirements. Decide which method to use based on data importance, network condition and performance requirements.

AMOVEDerrorindicatesapermanentkeyrelocationduetoclustertopologychanges,requiringclientstoupdateslot-to-nodemappingsandretryonthenewnode.1.MOVEDresponsesincludetheslotnumberandnewnodeaddress.2.Clientsshouldupdateinternalmappingsandredirectrequestsacco