{"id":5393,"date":"2026-04-17T21:20:34","date_gmt":"2026-04-17T12:20:34","guid":{"rendered":"https:\/\/www.freelifemakers.org\/wordpress\/?p=5393"},"modified":"2026-04-17T21:25:30","modified_gmt":"2026-04-17T12:25:30","slug":"webserver-httplib-webserver-load-balancer","status":"publish","type":"post","link":"https:\/\/www.freelifemakers.org\/wordpress\/index.php\/2026\/04\/17\/webserver-httplib-webserver-load-balancer\/","title":{"rendered":"[Webserver]httplib webserver+Load Balancer(Round Robin)"},"content":{"rendered":"\n

\ud83d\udc49\ud83c\udffb \ub85c\ub4dc \ubc38\ub7f0\uc11c\ub294 \uc560\ud50c\ub9ac\ucf00\uc774\uc158(\uc6f9 \uc11c\ube44\uc2a4 \ub4f1)\uc758 \uc694\uccad\uc744 \uc5ec\ub7ec \uc11c\ubc84\ub85c \ubd84\uc0b0(\ub85c\ub4dc \ubc38\ub7f0\uc2f1)\ud558\uc5ec, \ud2b9\uc815 \uc11c\ubc84\uc5d0 \ubd80\ud558\uac00 \uc9d1\uc911\ub418\uc9c0 \uc54a\ub3c4\ub85d \ud558\uace0 \uac00\uc6a9\uc131\uacfc \uc548\uc815\uc131\uc744 \ub192\uc774\ub294 \uc7a5\uce58 \ub610\ub294 \uc18c\ud504\ud2b8\uc6e8\uc5b4\uc785\ub2c8\ub2e4.
A load balancer is a device or software that distributes requests from applications (such as web services) across multiple servers (load balancing) to prevent the load from being concentrated on a specific server and to increase availability and stability.<\/p>\n\n\n\n

\ud83d\udc49\ud83c\udffb \ub85c\ub4dc\ubc38\ub7f0\uc2f1\uc758 \ubc29\ubc95\uc740 \uc5ec\ub7ec\uac00\uc9c0\uac00 \uc788\uc9c0\ub9cc \uc5ec\uae30\uc11c\ub294 \uc694\uccad\uc744 \uc21c\ucc28\uc801\uc73c\ub85c \uc5ec\ub7ec \uc11c\ubc84\uc5d0 \ubd84\ubc30\ud558\ub294 \ub77c\uc6b4\ub4dc \ub85c\ube48\ubc29\uc2dd\uc744 \uad6c\ud604\ud569\ub2c8\ub2e4.
There are various load balancing methods, but here we implement the Round Robin method, which distributes requests sequentially to multiple servers.<\/p>\n\n\n\n

\ud83d\udc49\ud83c\udffb \uc989 \ub85c\ub4dc\ubc38\ub7f0\uc11c\uc640 \uc5ec\ub7ec\uac1c\uc758 \uc6f9\uc11c\ubc84\uc5d0 \ub3d9\uc77c\ud55c \uc6f9\uc0ac\uc774\ud2b8\ub97c \ub9cc\ub4e4\uc5b4\uc11c \uc2e4\ud589\ud574\ub193\uace0 \ud074\ub77c\uc774\uc5b8\ud2b8\uac00 \uc811\uc18d\ud558\uba74 \ub85c\ub4dc\ubc38\ub7f0\uc11c\uac00 \uc5b4\ub5a4 \uc6f9\uc11c\ubc84\uc5d0 \uc811\uc18d\ud560\uc9c0 \uacb0\uc815\ud574\uc11c \uc811\uc18d\ud558\ub3c4\ub85d \ub3c4\uc640 \uc90d\ub2c8\ub2e4.
In other words, the same website is created and run on multiple web servers along with a load balancer, and when a client connects, the load balancer determines which web server to connect to and assists in the connection.<\/p>\n\n\n\n

\ud83d\udc49\ud83c\udffb \uc544\ub798\ub294 \uc811\uc18d\ud655\uc778\uc744 \uc704\ud574\uc11c \uc6f9\uc11c\ubc84 \ud654\uba74\uc5d0 \uac01 \uad6c\ubd84 \uba54\uc138\uc9c0\uac00 \ucd94\uac00\ub418\uc5b4 \uc788\uc2b5\ub2c8\ub2e4.
Below, each distinction message has been added to the web server screen to verify the connection.<\/p>\n\n\n\n

\ud83d\udc49\ud83c\udffb \ud130\ubbf8\ub110\uc5d0 \ucd1d 4\uac1c\uc758 \uc11c\ubc84\ub97c \uc2e4\ud589\ud569\ub2c8\ub2e4.
Run a total of 4 servers in the terminal.<\/p>\n\n\n\n

\u2714\ufe0f \ub85c\ub4dc\ubc38\ub7f0\uc11c 1\uac1c,\uc6f9\uc11c\ubc84\uc6a9 3\uac1c
1 load balancer, 3 for web servers<\/p>\n\n\n\n

\ud83d\udc49\ud83c\udffbhttplib.h(0.42.0) \ub2e4\uc6b4\ub85c\ub4dc \/ download<\/p>\n\n\n\n

curl -L https:\/\/raw.githubusercontent.com\/yhirose\/cpp-httplib\/master\/httplib.h -o httplib.h<\/code><\/pre>\n\n\n\n
\ud83d\udc49\ud83c\udffb \ub85c\ub4dc\ubc38\ub7f0\uc11c \/ Load Balancer<\/p>\n\n\n\n
\u2714\ufe0f \ucf54\ub4dc \/ code<\/p>\n\n\n\n
#include \"httplib.h\"\n#include <atomic>\n#include <iostream>\n#include <string>\n#include <vector>\n\nstruct Backend {\n    std::string host;\n    int port;\n};\n\nstatic void copy_response(const httplib::Result& r, httplib::Response& res) {\n    if (!r) {\n        res.status = 502;\n        res.set_content(\"Bad Gateway\", \"text\/plain; charset=utf-8\");\n        return;\n    }\n\n    res.status = r->status;\n    for (const auto& h : r->headers) {\n  \n        if (h.first == \"Connection\" || h.first == \"Keep-Alive\" ||\n            h.first == \"Proxy-Authenticate\" || h.first == \"Proxy-Authorization\" ||\n            h.first == \"TE\" || h.first == \"Trailers\" ||\n            h.first == \"Transfer-Encoding\" || h.first == \"Upgrade\") {\n            continue;\n        }\n        res.set_header(h.first.c_str(), h.second.c_str());\n    }\n    res.body = r->body;\n}\n\nint main() {\n    httplib::Server lb;\n\n    std::vector<Backend> backends = {\n        {\"127.0.0.1\", 3001},\n        {\"127.0.0.1\", 3002},\n        {\"127.0.0.1\", 3003}\n    };\n\n    std::atomic<size_t> rr{0};\n\n    auto next_backend = [&]() -> Backend {\n        size_t idx = rr.fetch_add(1, std::memory_order_relaxed) % backends.size();\n        return backends[idx];\n    };\n\n    auto proxy = [&](const httplib::Request& req, httplib::Response& res) {\n        Backend b = next_backend();\n        httplib::Client cli(b.host, b.port);\n\n        httplib::Headers headers = req.headers;\n        headers.erase(\"Host\");\n\n        std::cout << \"[LB] \" << req.method << \" \" << req.path\n                  << \" -> \" << b.host << \":\" << b.port << \"\\n\";\n\n        if (req.method == \"GET\") {\n            copy_response(cli.Get(req.path.c_str(), headers), res);\n        } else if (req.method == \"POST\") {\n            copy_response(cli.Post(req.path.c_str(), headers, req.body,\n                                   req.get_header_value(\"Content-Type\").c_str()), res);\n        } else if (req.method == \"PUT\") {\n            copy_response(cli.Put(req.path.c_str(), headers, req.body,\n                                  req.get_header_value(\"Content-Type\").c_str()), res);\n        } else if (req.method == \"PATCH\") {\n            copy_response(cli.Patch(req.path.c_str(), headers, req.body,\n                                    req.get_header_value(\"Content-Type\").c_str()), res);\n        } else if (req.method == \"DELETE\") {\n            copy_response(cli.Delete(req.path.c_str(), headers, req.body,\n                                     req.get_header_value(\"Content-Type\").c_str()), res);\n        } else {\n            res.status = 405;\n            res.set_content(\"Method Not Allowed\", \"text\/plain; charset=utf-8\");\n        }\n    };\n\n    lb.Get(R\"(.*)\", proxy);\n    lb.Post(R\"(.*)\", proxy);\n    lb.Put(R\"(.*)\", proxy);\n    lb.Patch(R\"(.*)\", proxy);\n    lb.Delete(R\"(.*)\", proxy);\n\n    std::cout << \"Round-robin LB listening on http:\/\/0.0.0.0:5080\\n\";\n    lb.listen(\"0.0.0.0\", 5080);\n}\n<\/code><\/pre>\n\n\n\n
\u2714\ufe0f \ub85c\ub4dc\ubc38\ub7f0\uc11c \ucef4\ud30c\uc77c \/ Load Balancer Compiling<\/p>\n\n\n\n
g++ lb_server.cpp -o lb_server -std=c++17 -pthread<\/code><\/pre>\n\n\n\n
\u2714\ufe0f \uc2e4\ud589 \/ Run<\/p>\n\n\n\n
.\/lb_server<\/code><\/pre>\n\n\n\n
\"\"
Load Balancer<\/figcaption><\/figure>\n\n\n\n
\ud83d\udc49\ud83c\udffb \ud0c0\uac9f \uc6f9\uc11c\ubc84 \/ Target Webserver<\/p>\n\n\n\n
\u2714\ufe0f \ucf54\ub4dc \/ Code<\/p>\n\n\n\n
#include \"httplib.h\"\n#include <atomic>\n#include <iostream>\n#include <string>\n\nint main(int argc, char* argv[]) {\n    if (argc < 3) {\n        std::cerr << \"usage: .\/target_server <server_id> <port>\\n\";\n        return 1;\n    }\n\n    const std::string server_id = argv[1];\n    const int port = std::stoi(argv[2]);\n\n    httplib::Server svr;\n    std::atomic<unsigned long long> hit{0};\n\n    svr.Get(\"\/\", [&](const httplib::Request&, httplib::Response& res) {\n        auto n = ++hit;\n        std::string html =\n            \"<!doctype html><html><head><meta charset='utf-8'><title>Target<\/title><\/head><body>\"\n            \"<h1>Target Server: \" + server_id + \"<\/h1>\"\n            \"<p>Port: \" + std::to_string(port) + \"<\/p>\"\n            \"<p>Hit Count: \" + std::to_string(n) + \"<\/p>\"\n            \"<p>\ube0c\ub77c\uc6b0\uc800\uc5d0\uc11c \uc0c8\ub85c\uace0\uce68\ud558\uba74 LB\uac00 \ub2e4\ub978 \uc11c\ubc84\ub85c \ubcf4\ub0bc \uc218 \uc788\uc2b5\ub2c8\ub2e4.<\/p>\"\n            \"<p>If you refresh the browser, the LB may send it to a different server.<\/p>\"\n            \"<\/body><\/html>\";\n\n        res.set_content(html, \"text\/html; charset=utf-8\");\n    });\n\n    std::cout << \"target \" << server_id << \" listening on http:\/\/0.0.0.0:\" << port << \"\\n\";\n    svr.listen(\"0.0.0.0\", port);\n}\n<\/code><\/pre>\n\n\n\n
\u2714\ufe0f \uc6f9\uc11c\ubc84 \ucef4\ud30c\uc77c \/ Webserver Compiling<\/p>\n\n\n\n
g++ target_server.cpp -o target_server -std=c++17 -pthread<\/code><\/pre>\n\n\n\n
\u2714\ufe0f \uc2e4\ud589 \/ Run<\/p>\n\n\n\n
— \ud130\ubbf8\ub110\uc744 3\uac1c \uc2e4\ud589\ud574\uc11c \uac01 \uc11c\ubc84\ub97c \uc2e4\ud589\ud569\ub2c8\ub2e4.
Run three terminals and run each server.<\/p>\n\n\n\n
.\/target_server A 3001\n.\/target_server B 3002\n.\/target_server C 3003<\/code><\/pre>\n\n\n\n
\"\"
Webserver<\/figcaption><\/figure>\n\n\n\n
\ud83d\udc49\ud83c\udffb \ube0c\ub77c\uc6b0\uc800 \uc811\uc18d \/ Browser access<\/p>\n\n\n\n
\u2714\ufe0fhttp:\/\/localhost:5080\uc73c\ub85c\uc811\uc18d\ud569\ub2c8\ub2e4.
Connect to http:\/\/localhost:5080.<\/p>\n\n\n\n
\u2714\ufe0f \ube0c\ub77c\uc6b0\uc800\ub97c \uc0c8\ub85c\uace0\uce68\ud558\uba74 \uc544\ub798\ucc98\ub7fc \ub2e4\ub978 \uc11c\ubc84\ub85c \uc811\uc18d\ub418\ub294\uac83\uc744 \ud655\uc778 \ud560 \uc218 \uc788\uc2b5\ub2c8\ub2e4.
If you refresh the browser, you can confirm that it connects to a different server as shown below.<\/p>\n\n\n\n
\u2b50\ufe0f hit count\ub294 \uadf8 \ud0c0\uac9f \uc11c\ubc84 \ud504\ub85c\uc138\uc2a4 \ud558\ub098 \uae30\uc900 \uc811\uc18d \ud69f\uc218<\/strong>\uc785\ub2c8\ub2e4.
The hit count is the number of connections per target server process.<\/p>\n\n\n\n
\n
\"\"
3001<\/figcaption><\/figure>\n\n\n\n
\"\"
3002<\/figcaption><\/figure>\n\n\n\n
\"\"
3003<\/figcaption><\/figure>\n<\/figure>\n\n\n\n
<\/p>\n","protected":false},"excerpt":{"rendered":"
\ud83d\udc49\ud83c\udffb \ub85c\ub4dc \ubc38\ub7f0\uc11c\ub294 \uc560\ud50c\ub9ac\ucf00\uc774\uc158(\uc6f9 \uc11c\ube44\uc2a4 \ub4f1)\uc758 \uc694\uccad\uc744 \uc5ec\ub7ec \uc11c\ubc84\ub85c \ubd84\uc0b0(\ub85c\ub4dc \ubc38\ub7f0\uc2f1)\ud558\uc5ec, \ud2b9\uc815 \uc11c\ubc84\uc5d0 \ubd80\ud558\uac00 \uc9d1\uc911\ub418\uc9c0 \uc54a\ub3c4\ub85d \ud558\uace0 \uac00\uc6a9\uc131\uacfc \uc548\uc815\uc131\uc744 \ub192\uc774\ub294 \uc7a5\uce58 \ub610\ub294 \uc18c\ud504\ud2b8\uc6e8\uc5b4\uc785\ub2c8\ub2e4.A load balancer is a device or software that distributes requests from applications (such as web services) across multiple servers (load balancing) to prevent the load from being concentrated on a specific server […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[23,1],"tags":[],"class_list":["post-5393","post","type-post","status-publish","format-standard","hentry","category-cpp","category-uncategorized","missing-thumbnail"],"_links":{"self":[{"href":"https:\/\/www.freelifemakers.org\/wordpress\/index.php\/wp-json\/wp\/v2\/posts\/5393","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.freelifemakers.org\/wordpress\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.freelifemakers.org\/wordpress\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.freelifemakers.org\/wordpress\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.freelifemakers.org\/wordpress\/index.php\/wp-json\/wp\/v2\/comments?post=5393"}],"version-history":[{"count":7,"href":"https:\/\/www.freelifemakers.org\/wordpress\/index.php\/wp-json\/wp\/v2\/posts\/5393\/revisions"}],"predecessor-version":[{"id":5405,"href":"https:\/\/www.freelifemakers.org\/wordpress\/index.php\/wp-json\/wp\/v2\/posts\/5393\/revisions\/5405"}],"wp:attachment":[{"href":"https:\/\/www.freelifemakers.org\/wordpress\/index.php\/wp-json\/wp\/v2\/media?parent=5393"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.freelifemakers.org\/wordpress\/index.php\/wp-json\/wp\/v2\/categories?post=5393"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.freelifemakers.org\/wordpress\/index.php\/wp-json\/wp\/v2\/tags?post=5393"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}