PSYNC command of redis

1. Redis Of PSYNC command
   1. SYNC Copy command
   2. PSYNC command
2. summary
3. ️ Thank you for your

Redis Of PSYNC command

The replication from the secondary server to the primary server is divided into initial replication and re replication after disconnection , The initial replication refers to that the slave server has not replicated any master server or that the master server to be replicated by the slave server is different from the master server replicated last time

The replication system after disconnection is that the master and slave servers interrupt the replication in the command propagation stage , After the secondary server reconnects to the primary server through automatic reconnection, continue to replicate the primary server .

SYNC Copy command

SYNC Copying commands is a resource intensive operation , Because the primary server needs to execute BGSAVE Command to generate RDB file , This build operation consumes a lot of the main server CPU、 Memory and disk IO resources , The master server will generate itself RDB Sending files to the slave server will consume a lot of network resources from the master and slave servers , Impact on the time when the primary server responds to command requests , receive RDB The slave server of the file needs to load the file sent by the master server RDB file , Command requests cannot be processed during load .

PSYNC command

Redis 2.8 Use later PSYNC Command instead of SYNC command ,PSYNC Complete resynchronization and partial resynchronization , Full resynchronization is used to handle initial replication , and SYNC The command steps are basically the same , Are created and sent by the master server RDB file , Send the write command saved in the buffer to the slave server for synchronization , Partial resynchronization is used to deal with the situation of duplication after disconnection ： When the slave server reconnects to the master server after disconnection , The master server sends the write command executed during the disconnection of the master server and the slave server to the slave server , As long as the slave server receives and executes these write commands, it can update the database to the current state of the master server .

SYNC The command needs to generate, transfer, and load the entire RDB file , Partial resynchronization only needs to send the missing write command from the slave server to the slave server for execution .

summary

In this article, we talked about Redis Copy , adopt redis Of SYNC Copy command import PSYNC command ,PSYNC replace SYNC The command has full resynchronization and partial resynchronization , I hope this article will help you

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