TTL and TTI in Java caching technology

TTL and TTI in Java caching technology

In any software system, caching technology is inseparable. As a common caching technology, Java cache can be divided into multiple types according to different caching strategies, such as memory-based, disk-based or cluster-based caching. Regardless of their type, caches often become more complex and more widely used. However, there are also some issues that need to be paid attention to when using caching technology, such as cache expiration time, namely TTL and TTI.

Introduction to TTL and TTI

TTL is Time-To-Live, which refers to the time interval from creation to expiration of cache items, usually in seconds. It means that when the difference between the creation time of a cache item and the current time is greater than the TTL, the cache item is considered to have expired and needs to be cleared or reloaded with new data.

TTI is Time-To-Idle (idle time), which refers to the time interval from the last access to the cache item to its expiration, and is often measured in seconds. It means that when the difference between the last access time of a cache item and the current time is greater than the TTI, the cache item is also considered to have expired and needs to be cleared or reloaded with new data.

Simply put, TTL is the time that elapses from the creation of the cache item to the elapse of the specified time interval, while TTI is the elapsed time from the last access to the elapse of the specified time interval.

The connection between TTL and TTI

Although the difference between TTL and TTI is small, their functions are different and they are often used at the same time.

TTL is mainly used to control the expiration time of elements in the cache, which can effectively avoid the presence of "dirty data" in the cache. For example, expired cache data is still in the cache, which seriously affects cache efficiency. The advantage of TTL is that it can ensure the freshness of cached data and allow us to obtain cached data faster. However, if the TTL is set too short, it will cause the cache to expire frequently and affect system performance.

TTI is mainly used to control the frequency of use of elements in the cache. It can effectively avoid the existence of "cold data" in the cache. For example, although the cached data has not expired, it has not been accessed for a long time and needs to be cleared or reset. Load new data. The advantage of TTI is that it can avoid frequent cache data invalidations and reduce the number of cached data reloads and system overhead. However, if the TTI is set too long, the cached data will not be fresh enough, affecting system performance.

How TTL and TTI are implemented

In Java cache, TTL and TTI can be implemented through cache implementation.

In Ehcache, setting the TTL and TTI of the cache element is very simple. You only need to set the corresponding attribute value in the cache element. For example, you can use the following method to set the TTL and TTI of a cached element:

CacheHelper.put(new Element(key, value, false, timeToLive, timeToIdle));

where timeToLive and timeToIdle represent the TTL and TTI of the element respectively.

In Guava Cache, you can simply set the TTL and TTI of cache elements through chain calls. For example, you can use the following methods to set the TTL and TTI of cached elements:

CacheBuilder.newBuilder()
           .expireAfterWrite(timeToLive, TimeUnit.SECONDS)
           .expireAfterAccess(timeToIdle, TimeUnit.SECONDS)
           .build();

Where expireAfterWrite and expireAfterAccess represent the TTL and TTI of the element respectively.

Summary

In Java caching, TTL and TTI are very useful caching strategies that can help us better control the expiration time and frequency of use of elements in the cache. However, the settings of TTL and TTI need to be adjusted according to the application scenario to avoid excessive impact on system performance. In addition, different cache implementation methods have different setting methods, which need to be selected according to the actual situation.

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