Redis overview
- 1. Redis cache Redis is a in-memory, key-value data store. it’s the most popular key-value data store, used by all big IT brands in this world. Amazon Elastic Cache supports Redis which makes redis a very powerful and must know key-value data store.
- 2. What Is In-Memory, Key- Value Store Key-Value store is a storage system where data is stored in form of key and value pairs. When we say in-memory key-value store, by that we mean that the key-value pairs are stored in primary memory(RAM). So we can say that Redis stored data in RAM in form of key-value pairs. In Redis, key has to be a string but value can be a string, list, set, sorted set or hash.
- 3. What Is In-Memory, Key- Value Store Lists: collections of string elements sorted according to the order of insertion. They are basically linked lists. Sets: collections of unique, unsorted string elements.
- 4. What Is In-Memory, Key- Value Store Sorted sets, similar to Sets but where every string element is associated to a floating number value, called score. The elements are always taken sorted by their score, so unlike Sets it is possible to retrieve a range of elements (for example you may ask: give me the top 10, or the bottom 10). Hashes, which are maps composed of fields associated with values. Both the field and the value are strings. This is very similar to Ruby or Python hashes
- 5. Advantage And Disadvantage of Redis over DBMS Database Management systems store everything in second storage which makes read and write operations very slow. But Redis stores everything in primary memory which is very fast in read and write of data.
- 6. Advantage And Disadvantage of Redis over DBMS Exceptionally fast − Redis is very fast and can perform about 110000 SETs per second, about 81000 GETs per second. Supports rich data types − Redis natively supports most of the datatypes that developers already know such as list, set, sorted set, and hashes. This makes it easy to solve a variety of problems as we know which problem can be handled better by which data type.
- 7. Advantage And Disadvantage of Redis over DBMS Operations are atomic − All Redis operations are atomic, which ensures that if two clients concurrently access, Redis server will receive the updated value. Multi-utility tool − Redis is a multi-utility tool and can be used in a number of use cases such as caching, messaging-queues (Redis natively supports Publish/Subscribe), any short-lived data in your application, such as web application sessions, web page hit counts, etc.
- 8. Advantage And Disadvantage of Redis over DBMS Primary memory is limited(much lesser size and expensive than secondary) therefore Redis cannot store large files or binary data. It can only store those small textual information which needs to be accessed, modified and inserted at a very fast rate.
- 9. Redis Single Instance Architecture Redis architecture contains two main processes: Redis client and Redis Server.
- 10. Redis Single Instance Architecture Redis client and server can be in the same computer or in two different computers. Redis server is responsible for storing data in memory. It handles all kinds of management and forms the major part of architecture. Redis client can be Redis console client or any other programming language’s Redis API.
- 11. Redis Single Instance Architecture As we saw that Redis stores everything in primary memory. Primary memory is volatile and therefore we will loose all stored data once we restart our Redis server or computer. Therefore we need a way for datastore persistance.
- 12. Redis Persistance There are two different ways to make Redis persistance: RDB and AOF .
- 13. Redis Persistance RDB Mechanism RDB makes a copy of all the data in memory and stores them in secondary storage(permanent storage). This happens in a specified interval. So there is chance that you will loose data that are set after RDB’s last snapshot.
- 14. Redis Persistance AOF AOF logs all the write operations received by the server. Therefore everything is persistance. The problem with using AOF is that it writes to disk for every operation and it is a expensive task and also size of AOF file is large than RDB file.
- 15. Redis Persistance You can use AOF and RDB together to get best persistance result.
- 16. Backup And Recovery Of Redis DataStore Redis does not provide any mechanism for datastore backup and recovery. Therefore if there is any hard disk crash or any other kind of disaster then all data will be lost. You need to use some third party server backup and recovery softwares to workaround it. If you are using Redis in a replicated environment then there is no need for backup.
- 17. Redis commands (SET) SET supports a set of options that modify its behavior: 1- EX seconds -- Set the specified expire time, in seconds Ex ( SETEX mykey 10 "Hello"). 2- PX milliseconds -- Set the specified expire time, in milliseconds. 3- NX -- Only set the key if it does not already exist.
- 18. Redis commands (GET) Get the value of key. If the key does not exist the special value nil is returned. An error is returned if the value stored at key is not a string, because GET only handles string values.
- 19. Redis commands (DEL) Removes the specified keys. A key is ignored if it does not exist.
- 20. Sets commands 1- SADD : Add the specified members to the set stored at key 2- SMEMBERS : Returns all the members of the set value stored at key. 3- SCARD : Returns the set cardinality (number of elements) of the set stored at key. 4- SDIFF : Returns the members of the set resulting from the difference between the first set and all the successive sets.
- 21. Hash commands HSET : Sets field in the hash stored at key to value. If key does not exist, a new key holding a hash is created. If field already exists in the hash, it is overwritten. ex : HSET myhash field1 "Hello" HDEL : Removes the specified fields from the hash stored at key. ex : HDEL myhash field1
- 22. Hash commands HGET : Returns the value associated with field in the hash stored at key. Ex : HGET myhash field1 HGETALL : Returns all fields and values of the hash stored at key. In the returned value, every field name is followed by its value, so the length of the reply is twice the size of the hash. Ex :HGETALL myhash
- 23. Who's using Redis? Twitter GitHub Weibo Pinterest Snapchat Craigslist Digg StackOverflow Flickr
- 24. Good bay Created by : Ahmad EL-Khuja [email protected]