重新启动后在Redis（或其他缓存服务）中重新加载数据的最佳方法？

Question

When the Redis server fails and restarts, what's the best way to reload data into Redis? (I'm a bit new to Redis and in-memory databases)

I have three parts, I'll describe them as follows:

• Producer app - Updates a SQL database and also writes a subset of the SQL data into a Redis server
• Redis server - Has an important subset of the SQL data
• Consumer app - Needs to look up data in Redis at a fast rate (currently doesn't write to Redis or the SQL database)

Some options I'm considering:

• Put reload script in Redis server so it'll query the SQL database and reload itself upon startup
• Build an endpoint in the Producer app that the Consumer app can call to tell the Producer app to reload Redis when the Consumer app notices that the Redis server is empty and has restarted
• Get rid of the Producer app completely and have the Consumer app directly query the SQL database and write the results in Redis (but then how will it know when the SQL data has been updated?)
• Keep the Producer app, but also have the Consumer app directly query the SQL database and write the results in Redis when the Consumer app senses Redis to be empty

Answer 1

Reloading data into Redis or any other cache is called cache-warming. The problem you seem to have is that you're not trying to use Redis as a cache but as a means to communicate between the apps.

Normally you would want your application to query Redis to see if there's data in there and if not query the endpoint or database so you should always have some kind of means to go without Redis.

Whether you have the producer purge the consumer's cache or have consumer mind it's own cache and deal with stale data or introduce another application just for serving the data would depends on your exact needs.