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This article focuses on "what are the common problems in the design of Java cache architecture". Interested friends may wish to take a look. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn what are the common problems in Java cache architecture design.

1 Design of hierarchical cache architecture

2 complexity problems caused by caching

Common problems include

Data consistency

Cache penetration

Cache avalanche

Cache highly available

The cache hotspot below describes and analyzes these problems and the corresponding solutions one by one.

Data consistency

Because caching is a copy of persisted data, data inconsistencies are inevitable. A condition that results in dirty reading or inability to read data. Data inconsistency, usually due to network instability or node failure

There are 3 common scenarios and solutions for problems:

Cache penetration

Cache generally exists in Key,value mode. When a Key does not exist, the database will be queried. If the Key does not exist, the database will be frequently requested, causing access pressure on the database.

Main solutions:

The data with empty results is also cached, and when the key has data, clean the cache.

Must not exist key, use Bloom filter to build a large Bitmap, query through the bitmap filter

Cache avalanche

Cache highly available

Whether the cache is highly available depends on the actual scenario. Not all businesses require high cache availability. You need to design the solution according to specific business conditions, such as whether the tipping point affects the backend database.

Main solutions:

Distributed: massive caching of data

Replication: achieving high availability of cached data nodes

Cache hotspot

Some particularly hot data, high concurrent access to the same cache data, resulting in excessive pressure on the cache server.

Solution: copy multiple cache copies, distribute requests to multiple cache servers, and reduce the pressure on a single cache server caused by cache hotspots

3 Industry cases

The case mainly refers to the technology sharing of Sina Weibo Chen Bo.

Technical challenge

Feed cache architecture diagram

Architectural features

Sina Weibo applies SSD to the distributed cache scenario, extending the traditional Redis/MC + Mysql mode to Redis/MC + SSD Cache + Mysql mode. SSD Cache is used as an L2 cache, which first reduces the problems of high cost and small capacity of MC/Redis, and also solves the database access pressure caused by penetrating DB.

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