The technical aspects of consistent hashing have been well explained in other places, and youre crazy and negligent if you use this as your only reference. But, Ill try to do my best. Consistent hashing is a technique that lets you smoothly handle these problems Consistent hashing provides an alternative to multicast and directory schemes, and has several other advantages in load balancing and fault tolerance. Its performance was analyzed theoretically in previous work in this paper we describe the implementation of a Set this value to consistent to enable consistent hashing which allows servers to be added or removed from the pool without causing keys to be remapped. The simplicity of consistent hashing is pretty mind-blowing. Here you have a number of nodes in a cluster of databases, or in a cluster of web caches. How do you figure out where the data for a particular key goes in that cluster? You apply a hash function to the key. Thats it? Consistent hashing is what we use when we want to distribute a set of keys along a span of key/value servers in awell consistent fashion. If you Google around to learn what consistent hashing means So you can see that almost all objects will hashed into a new location. This will be a disaster since the originating content servers are swamped with requests from the cache machines. And this is why you need consistent hashing. libketama is a consistent hashing library written in C. You supply a list of servers and ketama will map keys to servers in a consistent way, even after adding or removing servers from the list. Альтернативой для данной функции является механизм консистентного хэширования ( consistent hashing), который при переконфигурации кластера сохраняет положение ключей по серверам. Consistent hashing allows distribution of data across a cluster to minimize reorganization when nodes are added or removed. Consistent hashing partitions data based on the partition key. In contrast, in most traditional hash tables, a change in the number of array slots causes nearly all keys to be remapped because the mapping between the keys and the slots is defined by a modularFor faster navigation, this Iframe is preloading the Wikiwand page for Consistent hashing. Консистентное хеширование (англ. consistent hashing) — это особый вид хеширования, отличающийся тем, что когда хеш-таблица перестраивается, только. ключей в среднем должны быть переназначены, где. — число ключей и. число слотов (slots, buckets).
By using consistent hashing, only K / n keys need to be remapped on average, where K is the number of keys, and n is the number of slots. Consistent hashing could play an increasingly important role as internet use increases and as distributed systems grow more prevalent. Решения Сервис-proxy перед memcached Consistent hashing. Цесько В. А. (CompSciCenter).Consistent hashing: своими руками. Будем отображать ключи в слоты, а затем слоты на машины You see with just a modulo on no of nodes a new node addition or removal creates a lot of movement of keys. With Consistent Hashing, you divide a key space into buckets (usually denoted by a ring) and let nodes in the cluster take ownership of key spaces. Consistent hashing is a scheme that provides hash table functionality in a way that the addition or removal of one slot does not significantly change the mapping of keys to slots. Primarily I would say the advantage of consistent hashing is when it comes to hotspots.
The idea has now been expanded to other areas also. Up next. Implementing Consistent Hashing - Georgia Tech - Network Congestion - Duration: 1:22.MIT 6.854 Spring 2016 Lecture 3: Consistent Hashing and Random Trees - Duration: 59:17. Consistent Hashing is a hashing technique whereby each bucket appears at multiple points throughout the hash space, and the bucket selected is the nearest higher (or lower, it doesnt matter, provided its consistent) bucket to the computed hash (and the hash space wraps around). Consistent hashing isnt the final word in distributed dictionaries, but its a good start. All the usual caveats apply to the post: Im still learning this stuff, and corrections, improvements, etcetera are welcome!