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146 lines
4.7 KiB
Plaintext
146 lines
4.7 KiB
Plaintext
//
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// Copyright (c) 2025 Marcelo Zimbres Silva (mzimbres@gmail.com)
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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[#intro]
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= Introduction
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Boost.Redis is a high-level https://redis.io/[Redis] and https://valkey.io/[Valkey]
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client library built on top of
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https://www.boost.org/doc/libs/latest/doc/html/boost_asio.html[Boost.Asio]
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that implements the Redis protocol
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https://github.com/redis/redis-specifications/blob/master/protocol/RESP3.md[RESP3].
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== Requirements
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The requirements for using Boost.Redis are:
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* Boost 1.84 or higher. Boost.Redis is included in Boost installations since Boost 1.84.
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* pass:[C++17] or higher. Supported compilers include gcc 11 and later, clang 11 and later, and Visual Studio 16 (2019) and later.
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* Redis 6 or higher, or Valkey (any version). The database server must support RESP3.
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We intend to maintain compatibility with both Redis and Valkey in the long-run.
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* OpenSSL.
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The documentation assumes basic-level knowledge about https://redis.io/docs/[Redis] and https://www.boost.org/doc/libs/latest/doc/html/boost_asio.html[Boost.Asio].
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== Building the library
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To use the library it is necessary to include the following:
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[source,cpp]
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----
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#include <boost/redis/src.hpp>
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----
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in exactly one source file in your applications. Otherwise, the library is header-only.
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Boost.Redis unconditionally requires OpenSSL. Targets using Boost.Redis need to link
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to the OpenSSL libraries.
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== Tutorial
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The code below uses a short-lived connection to
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https://redis.io/commands/ping/[ping] a Redis server:
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[source,cpp]
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----
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#include <boost/redis/connection.hpp>
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#include <boost/asio/co_spawn.hpp>
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#include <boost/asio/consign.hpp>
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#include <boost/asio/detached.hpp>
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#include <iostream>
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namespace net = boost::asio;
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using boost::redis::request;
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using boost::redis::response;
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using boost::redis::config;
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using boost::redis::connection;
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auto co_main(config const& cfg) -> net::awaitable<void>
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{
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auto conn = std::make_shared<connection>(co_await net::this_coro::executor);
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conn->async_run(cfg, {}, net::consign(net::detached, conn));
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// A request containing only a ping command.
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request req;
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req.push("PING", "Hello world");
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// Response object.
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response<std::string> resp;
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// Executes the request.
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co_await conn->async_exec(req, resp);
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conn->cancel();
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std::cout << "PING: " << std::get<0>(resp).value() << std::endl;
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}
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----
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The roles played by the `async_run` and `async_exec` functions are:
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* xref:reference:boost/redis/basic_connection/async_exec-02.adoc[`connection::async_exec`]: executes the commands contained in the
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request and stores the individual responses in the response object. Can
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be called from multiple places in your code concurrently.
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* xref:reference:boost/redis/basic_connection/async_run-04.adoc[`connection::async_run`]: keeps the connection healthy. It takes care of hostname resolution, session establishment, health-checks, reconnection and coordination of low-level read and write operations. It should be called only once per connection, regardless of the number of requests to execute.
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== Server pushes
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Redis servers can also send a variety of pushes to the client. Some of
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them are:
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* https://redis.io/docs/manual/pubsub/[Pubsub messages].
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* https://redis.io/docs/manual/keyspace-notifications/[Keyspace notifications].
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* https://redis.io/docs/manual/client-side-caching/[Client-side caching].
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The connection class supports server pushes by means of the
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xref:reference:boost/redis/basic_connection/async_receive.adoc[`connection::async_receive2`] function, which can be
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called in the same connection that is being used to execute commands.
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The coroutine below shows how to use it
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[source,cpp]
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----
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auto
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receiver(std::shared_ptr<connection> conn) -> net::awaitable<void>
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{
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request req;
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req.push("SUBSCRIBE", "channel");
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flat_tree resp;
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conn->set_receive_response(resp);
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// Loop while reconnection is enabled
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while (conn->will_reconnect()) {
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// Reconnect to channels.
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co_await conn->async_exec(req);
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// Loop reading Redis pushes.
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for (error_code ec;;) {
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co_await conn->async_receive2(resp, redirect_error(ec));
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if (ec)
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break; // Connection lost, break so we can reconnect to channels.
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// Use the response here and then clear it.
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...
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resp.clear();
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}
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}
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}
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----
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== Further reading
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Here is a list of topics that you might be interested in:
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* xref:cancellation.adoc[Setting timeouts to requests and managing cancellation].
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* xref:requests_responses.adoc[More on requests and responses].
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* xref:serialization.adoc[Serializing and parsing into custom types].
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* xref:logging.adoc[Configuring logging].
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* xref:examples.adoc[Examples].
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