Caching in C++: Redis, Memcached, and Built-in Solutions

Caching in C++: Redis and Other Tools

Caching is one of the key techniques for optimizing the performance of C++ applications. It reduces data access time and lowers the load on databases and external services. In this article, we will explore the main libraries and tools for implementing caching in C++: from industrial solutions based on Redis and Memcached to lightweight built-in implementations.

1. Redis and its C++ Clients

Redis is a high-performance in-memory key-value data store, often used as a cache. Two main libraries are available for working with Redis from C++:

1.1. hiredis

hiredis is a minimalistic C library officially supported by Redis. It provides both synchronous and asynchronous APIs.

Installation:

# Ubuntu/Debiansudo apt install libhiredis-dev

# macOSbrew install hiredis

# Build from sourcegit clone https://github.com/redis/hiredis.gitcd hiredis && make && sudo make install

Usage example (synchronous mode):

#include <hiredis/hiredis.h>#include <iostream>

int main() {    redisContext *c = redisConnect("127.0.0.1", 6379);    if (c == nullptr || c->err) {        std::cerr << "Connection error: " << c->errstr << std::endl;        return 1;    }

    // Set value    redisReply *reply = (redisReply*)redisCommand(c, "SET key1 value1");    freeReplyObject(reply);

    // Get value    reply = (redisReply*)redisCommand(c, "GET key1");    if (reply->type == REDIS_REPLY_STRING) {        std::cout << "Value: " << reply->str << std::endl;    }    freeReplyObject(reply);

    redisFree(c);    return 0;}

1.2. redis-plus-plus

redis-plus-plus is a modern C++17 wrapper over hiredis with a convenient interface, support for connection pools, transactions, and pub/sub.

Installation:

git clone https://github.com/sewenew/redis-plus-plus.gitcd redis-plus-plusmkdir build && cd buildcmake -DREDIS_PLUS_PLUS_CXX_STANDARD=17 ..make && sudo make install

Example:

#include <sw/redis++/redis++.h>#include <iostream>

int main() {    sw::redis::Redis redis("tcp://127.0.0.1:6379");

    // Set with TTL (time-to-live 60 seconds)    redis.setex("session:user1", 60, "active");

    // Get    auto val = redis.get("session:user1");    if (val) {        std::cout << "Session: " << *val << std::endl;    }

    // Check existence    bool exists = redis.exists("session:user1");    std::cout << "Exists: " << std::boolalpha << exists << std::endl;

    return 0;}

2. Memcached and libmemcached

Memcached is another popular in-memory store, optimized for caching small objects. The main C++ library is libmemcached.

Installation:

sudo apt install libmemcached-dev

# Build from sourcegit clone https://github.com/awesomized/libmemcached.gitcd libmemcached && ./configure && make && sudo make install

Example:

#include <libmemcached/memcached.h>#include <iostream>#include <cstring>

int main() {    memcached_st *memc = memcached_create(nullptr);    memcached_server_st *servers = memcached_server_list_append(nullptr, "127.0.0.1", 11211, nullptr);    memcached_server_push(memc, servers);    memcached_server_list_free(servers);

    // Write    const char *key = "cache_key";    const char *value = "cached_value";    memcached_return_t rc = memcached_set(memc, k