基于协同过滤推荐算法的在线教育平台（前后端分离）

This README is just a fast *quick start* document. You can find more detailed documentation at [redis.io](https://redis.io). What is Redis? -------------- Redis is often referred as a *data structures* server. What this means is that Redis provides access to mutable data structures via a set of commands, which are sent using a *server-client* model with TCP sockets and a simple protocol. So different processes can query and modify the same data structures in a shared way. Data structures implemented into Redis have a few special properties: * Redis cares to store them on disk, even if they are always served and modified into the server memory. This means that Redis is fast, but that is also non-volatile. * Implementation of data structures stress on memory efficiency, so data structures inside Redis will likely use less memory compared to the same data structure modeled using an high level programming language. * Redis offers a number of features that are natural to find in a database, like replication, tunable levels of durability, cluster, high availability. Another good example is to think of Redis as a more complex version of memcached, where the operations are not just SETs and GETs, but operations to work with complex data types like Lists, Sets, ordered data structures, and so forth. If you want to know more, this is a list of selected starting points: * Introduction to Redis data types. http://redis.io/topics/data-types-intro * Try Redis directly inside your browser. http://try.redis.io * The full list of Redis commands. http://redis.io/commands * There is much more inside the Redis official documentation. http://redis.io/documentation Building Redis -------------- Redis can be compiled and used on Linux, OSX, OpenBSD, NetBSD, FreeBSD. We support big endian and little endian architectures, and both 32 bit and 64 bit systems. It may compile on Solaris derived systems (for instance SmartOS) but our support for this platform is *best effort* and Redis is not guaranteed to work as well as in Linux, OSX, and \*BSD there. It is as simple as: % make You can run a 32 bit Redis binary using: % make 32bit After building Redis, it is a good idea to test it using: % make test Fixing build problems with dependencies or cached build options --------- Redis has some dependencies which are included into the `deps` directory. `make` does not automatically rebuild dependencies even if something in the source code of dependencies changes. When you update the source code with `git pull` or when code inside the dependencies tree is modified in any other way, make sure to use the following command in order to really clean everything and rebuild from scratch: make distclean This will clean: jemalloc, lua, hiredis, linenoise. Also if you force certain build options like 32bit target, no C compiler optimizations (for debugging purposes), and other similar build time options, those options are cached indefinitely until you issue a `make distclean` command. Fixing problems building 32 bit binaries --------- If after building Redis with a 32 bit target you need to rebuild it with a 64 bit target, or the other way around, you need to perform a `make distclean` in the root directory of the Redis distribution. In case of build errors when trying to build a 32 bit binary of Redis, try the following steps: * Install the packages libc6-dev-i386 (also try g++-multilib). * Try using the following command line instead of `make 32bit`: `make CFLAGS="-m32 -march=native" LDFLAGS="-m32"` Allocator --------- Selecting a non-default memory allocator when building Redis is done by setting the `MALLOC` environment variable. Redis is compiled and linked against libc malloc by default, with the exception of jemalloc being the default on Linux systems. This default was picked because jemalloc has proven to have fewer fragmentation problems than libc malloc. To force compiling against libc malloc, use: % make MALLOC=libc To compile against jemalloc on Mac OS X systems, use: % make MALLOC=jemalloc Verbose build ------------- Redis will build with a user friendly colorized output by default. If you want to see a more verbose output use the following: % make V=1 Running Redis ------------- To run Redis with the default configuration just type: % cd src % ./redis-server If you want to provide your redis.conf, you have to run it using an additional parameter (the path of the configuration file): % cd src % ./redis-server /path/to/redis.conf It is possible to alter the Redis configuration by passing parameters directly as options using the command line. Examples: % ./redis-server --port 9999 --replicaof 127.0.0.1 6379 % ./redis-server /etc/redis/6379.conf --loglevel debug All the options in redis.conf are also supported as options using the command line, with exactly the same name. Playing with Redis ------------------ You can use redis-cli to play with Redis. Start a redis-server instance, then in another terminal try the following: % cd src % ./redis-cli redis> ping PONG redis> set foo bar OK redis> get foo "bar" redis> incr mycounter (integer) 1 redis> incr mycounter (integer) 2 redis> You can find the list of all the available commands at http://redis.io/commands. Installing Redis ----------------- In order to install Redis binaries into /usr/local/bin just use: % make install You can use `make PREFIX=/some/other/directory install` if you wish to use a different destination. Make install will just install binaries in your system, but will not configure init scripts and configuration files in the appropriate place. This is not needed if you want just to play a bit with Redis, but if you are installing it the proper way for a production system, we have a script doing this for Ubuntu and Debian systems: % cd utils % ./install_server.sh The script will ask you a few questions and will setup everything you need to run Redis properly as a background daemon that will start again on system reboots. You'll be able to stop and start Redis using the script named `/etc/init.d/redis_<portnumber>`, for instance `/etc/init.d/redis_6379`. Code contributions ----------------- Note: by contributing code to the Redis project in any form, including sending a pull request via Github, a code fragment or patch via private email or public discussion groups, you agree to release your code under the terms of the BSD license that you can find in the [COPYING][1] file included in the Redis source distribution. Please see the [CONTRIBUTING][2] file in this source distribution for more information. [1]: https://github.com/antirez/redis/blob/unstable/COPYING [2]: https://github.com/antirez/redis/blob/unstable/CONTRIBUTING Redis internals === If you are reading this README you are likely in front of a Github page or you just untarred the Redis distribution tar ball. In both the cases you are basically one step away from the source code, so here we explain the Redis source code layout, what is in each file as a general idea, the most important functions and structures inside the Redis server and so forth. We keep all the discussion at a high level without digging into the details since this document would be huge otherwise and our code base changes continuously, but a general idea should be a good starting point to understand more. Moreover most of the code is heavily commented and easy to follow. Source code layout --- The Redis root directory just contains this README, the Makefile which calls the real Makefile inside the `src` directory and an example configuration for Redis and Sentinel. You can find a few shell scripts that are used in order to execute the Redis, Redis Cluster and Redis Sentinel unit tests, which are implemented inside the `tests` directory. Inside the root are the following important directories: * `src`: contains the Red