evpp is a modern C++ network library for developing high performance network services using TCP/UDP/HTTP protocols. evpp provides a TCP Server to support multi-threaded nonblocking event-driven server and also a HTTP, UDP Server to support HTTP and UDP protocols.

1. Modern C++11 interface
2. Modern functional/bind style callback instead of C-style function pointer.
3. Multi-core friendly and thread-safe
4. A nonblocking multi-threaded TCP server
5. A nonblocking TCP client
6. A nonblocking multi-threaded HTTP server based on the buildin http server of libevent
7. A nonblocking HTTP client
8. A nonblocking multi-threaded UDP server
9. Async DNS resolving
10. EventLoop/ThreadPool/Timer
11. Well tested — evpp is well tested with unit tests and stress tested daily in production. It has been used in production and processes 1000+ billions networking communications every day in our production
12. Easy install — evpp can be packaged as a deb, rpm, tar.gz with a single command for straight forward distribution and integration

And also provides some libraries based on evpp:

1. evmc a nonblocking async C++ memcached (or membase cluster) client library. This library is currently used in production which sends more than 300 billions requests every day. See evmc readme for more details.
2. evnsq a nonblocking async C++ NSQ client library. This library is currently used in production which processes more than 130 billions messages every day. See evnsq readme for more details.

NOTE: master is our development branch and may not be stable at all times.

In our business system, we need to build a TCP long-connection Gateway and other TCP services. When we do a survey of the open sources, we cannot find any appropriate network library for our demands. According to our own business characteristic, an ideal C++ network library must have the features below:

1. A simple enough C++ interface
2. Support multi-threads and multi-processes
3. Based on libevent is preferable for our projects. Given your older applications were based on libevent, it was preferable to have your new framework also be based on it, so as to reduce the overall time/effort/cost to completion. Actually, we do have some older applications which were based on libevent.

As described above, there are not many options to choose from. So we developed one ourself. The design of the interface is highly inspired by muduo and Golang. Let's take some examples to exaplain this:

1. Duration : This is a time inteval class, with a time unit. It is referenced to the implementation of Duration of the Golang project. We have seen some many cases that the time interval without a unit. For example, what does timeout mean? Seconds, milliseconds or microseconds? We need to read the document carefully, even more, we need to read the implementation codes. Our Duration class has self-explations with the time unit. Additionally std::chrono::duration in the STL of C++11 has the similar implementations, but it is a little bit complicated.
2. Buffer : This is a memory buffer class. It uses the advantages of the two projects muduo and Golang.
3. http::Server : This is a HTTP server class with a working threads pool. It is thread-safe to dispatch tasks
4. We simply use a string with the format of "ip:port" to represent a network address. This is referenced to the design of Golang.
5. httpc::ConnPool : This is HTTP client connection pool with highly performance. In the future we can add more features to this class : load balance and failover.

In addition, in the implematations we pay seriously attations to thread-safe problems. An event-related resource must be initialized and released in its own EventLoop thread, so that we can minimize the possibility of thread-safe error. In order to achieve this goal we reimplemented event_add and event_del and other functions. Each call to event_add, we stored the resource into thread local storage, and in the call event_del, we checked it whether it is stored in the thread local storage. And then we checked all the threads local storages to see whether there are resources not destructively released when the process was exiting. The detail codes are here https://github.com/Qihoo360/evpp/blob/master/evpp/inner_pre.cc#L36~L87. We are so harshly pursuit the thread safety to make a program can quietly exit or reload, because we have a deep understanding of "developing a system to run forever and developing a system to quietly exit after running a period of time are totally two different things".

Please see Quick Start

The IO Event performance benchmark against Boost.Asio : evpp is higher than asio about 20%~50% in this case

The ping-pong benchmark against Boost.Asio : evpp is higher than asio about 5%~20% in this case

The throughput benchmark against libevent2 : evpp is higher than libevent about 17%~130% in this case

The throughput benchmark against Boost.Asio : evpp and asio have the similar performance in this case

The throughput benchmark against Boost.Asio(中文) : evpp and asio have the similar performance in this case

The throughput benchmark against muduo(中文) : evpp and muduo have the similar performance in this case

The throughput benchmark of evpp is 17%~130% higher than libevent2 and similar with boost.asio and muduo. Although evpp is based on libevent, evpp has a better throughput benchmark than libevent. That's because evpp implements its own IO buffer instead of libevent's evbuffer.

#include <evpp/tcp_server.h>
#include <evpp/buffer.h>
#include <evpp/tcp_conn.h>

int main(int argc, char* argv[]) {
    std::string addr = "0.0.0.0:9099";
    int thread_num = 4;
    evpp::EventLoop loop;
    evpp::TCPServer server(&loop, addr, "TCPEchoServer", thread_num);
    server.SetMessageCallback([](const evpp::TCPConnPtr& conn,
                                 evpp::Buffer* msg,
                                 evpp::Timestamp ts) {
        conn->Send(msg);
    });
    server.SetConnectionCallback([](const evpp::TCPConnPtr& conn) {
        if (conn->IsConnected()) {
            LOG_INFO << "A new connection from " << conn->remote_addr();
        } else {
            LOG_INFO << "Lost the connection from " << conn->remote_addr();
        }
    });
    server.Init();
    server.Start();
    loop.Run();
    return 0;
}

#include <evpp/http/http_server.h>

int main(int argc, char* argv[]) {
    std::vector<int> ports = { 9009, 23456, 23457 };
    int thread_num = 2;
    evpp::http::Server server(thread_num);
    server.RegisterHandler("/echo",
                           [](evpp::EventLoop* loop,
                              const evpp::http::ContextPtr& ctx,
                              const evpp::http::HTTPSendResponseCallback& cb) {
        cb(ctx->body().ToString()); }
    );
    server.Init(ports);
    server.Start();
    while (!server.IsStopped()) {
        usleep(1);
    }
    return 0;
}

#include <evpp/udp/udp_server.h>
#include <evpp/udp/udp_message.h>

int main(int argc, char* argv[]) {
    std::vector<int> ports = { 1053, 5353 };
    evpp::udp::Server server;
    server.SetMessageHandler([](evpp::EventLoop* loop, evpp::udp::MessagePtr& msg) {
        evpp::udp::SendMessage(msg);
    });
    server.Init(ports);
    server.Start();

    while (!server.IsStopped()) {
        usleep(1);
    }
    return 0;
}

Please see the source code in examples.

1. An async redis client
2. Add zipkin tracing support
3. Add examples : asio chat room
4. Fix the comments written in mandarin problem
5. Add benchmark against with boost.asio/cpp-netlib/beast http library/muduo/libevent/libuv ...

Welcome to join this list :-)

Thanks for the support of Qihoo360.

Thanks for libevent, glog, gtest, Golang, LevelDB, rapidjson projects.

evpp is highly inspired by muduo. Thanks Chen Shuo