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This article introduces the relevant knowledge of "what are the problems in caching". Many people will encounter such a dilemma in the operation of actual cases. then let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

The normal processing flow for caching is as follows:

The system first obtains the data from the cache, and if the data is successfully obtained, it will return the data directly.

If you don't get it, get it from the database. After getting it normally from the database, update the data into the cache and return the normal data.

If no data is obtained from the database, empty data is returned.

Several problems with caching: cache avalanche:

The original cache is invalid, and during the period when the latest cached data is not cached, all the requests for obtaining data from the cache have gone to query the database.

It puts great pressure on database CPU and memory, which can cause database downtime seriously.

Solution:

The expiration time of cached data is set randomly to avoid a large number of cache expires at the same time.

If the cached data is distributed, the hot spot data is evenly distributed in different cached databases.

Set hotspot data to never expire

Cache traversal:

Refers to the data queried by the user, which does not exist in the database or in the cache. However, users continue to query, resulting in excessive pressure on the database.

Solution:

The interface layer adds a check, and carries on the basic check for the query data. If it does not comply with the rules, it will be rejected directly.

If the data cannot be obtained from the cache and cannot be found in the database, the key-value pair can be written as key-null and cached.

Cache warm-up:

After the system is online, load the relevant cache data directly into the cache system, which can avoid querying the database first and then setting the

The problem with data caching.

Cache updates:

In addition to the cache invalidation strategy that comes with the cache server, we can also customize cache elimination for specific business scenarios.

Common strategies are as follows:

Regularly clean up expired caches.

When the user requests data, determine whether the cache used in the request expires, and update the cache directly if it expires.

Cache degradation:

When there is a sharp increase in traffic, when there is a problem with the service, or when the non-core service affects the performance of the core process, it is still necessary to ensure that the service is available, which is immediately detrimental to the service.

The system can be degraded automatically according to some key data, or the switch can be configured to achieve manual degradation.

The ultimate goal of downgrading is to ensure the availability of core services.

Some services time out due to network jitter or when the service is online and are downgraded.

The success rate of some services fluctuates over a period of time and can be downgraded automatically or manually to send system alarms.

If the service is unavailable or the service data is confused, an emergency manual downgrade is required

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