When Redis loses data upon restart, the usual reasons are misconfiguration of Redis or incorrect asynchronous options. Redis fundamentally supports data persistence to disk through the use of Memory Snapshot (RDB) or Append-Only File (AOF) mechanisms to ensure data is not lost after a restart.
Below are some common reasons and ways to avoid data loss upon Redis restart:
Deactivated persistence mechanism
By default, Redis does not activate data persistence to disk. This can lead to data loss when you restart Redis. To address this issue, ensure that you have enabled data persistence to disk by using RDB or AOF configurations.
Using the wrong persistence mechanism
If you have enabled data persistence, ensure that you have chosen the appropriate persistence mechanism that suits your specific requirements. Redis provides two persistence mechanisms, RDB and AOF. RDB stores data as a snapshot file at regular intervals, while AOF stores commands that append to the database. Choose the persistence mechanism that suits your environment and specific needs.
Inadequate snapshotting interval
If you have enabled RDB persistence, ensure that the snapshotting interval is configured correctly. If the snapshotting interval is too long, you may lose data between the last snapshot and the Redis restart. If it is too short, it could impact the performance of Redis.
Incorrect asynchronous options
If you have enabled AOF persistence, ensure that the asynchronous options are correctly configured. Redis supports asynchronous options like always, everysec and no. The always option ensures immediate asynchronous writing, while everysec writes asynchronously once per second.
To avoid data loss upon Redis restart, check and ensure that your configurations are properly set up and aligned with your application's requirements. If you are unsure, learn more about Redis configurations and persistence options to ensure data durability and safety.