架构师训练营 Week 05 作业

namespace ConsistenHashing{    class HashRing    {    public:        void addNode(const std::string &nodeKey, int virtualNums)        {            for (int i = 0; i < virtualNums; i++)            {                nodeMap.emplace(getHash(nodeKey + std::to_string(i)), nodeKey);            }        }
        void removeNode(const std::string &nodeKey)        {            auto finder = [&](decltype(nodeMap)::const_reference pair) { return nodeKey == pair.second; };
            for (auto it = nodeMap.begin(); (it = std::find_if(it, nodeMap.end(), finder)) != nodeMap.end(); ++it)            {                nodeMap.erase(it);            }        }
        std::string getNode(const std::string &nodeKey)        {            if (nodeMap.empty())                return "";
            auto greater = nodeMap.upper_bound(getHash(nodeKey));
            if (nodeMap.end() != greater)            {                return greater->second;            }            else            {                return nodeMap.begin()->second;            }        }
    private:        static uint32_t getHash(const std::string &key)        {            std::size_t hash = std::hash<std::string>{}(key);            return static_cast<uint32_t>(hash % 0xffff'ffff);        }
        std::map<uint32_t, std::string> nodeMap;    };
} // namespace ConsistenHashing

using namespace std;using namespace ConsistenHashing;
int main(int argc, char **argv){    // Host IPs    vector<string> nodeList{        "192.168.100.101",        "192.168.100.102",        "192.168.100.103",        "192.168.100.104",        "192.168.100.105",        "192.168.100.106",        "192.168.100.107",        "192.168.100.108",        "192.168.100.109",        "192.168.100.110"};
    // Create a hash ring    HashRing hashRing;    for (auto &node : nodeList)    {        hashRing.addNode(node, 200);    }
    //    map<string, int> counting;    for (auto &node : nodeList)    {        counting.emplace(node, 0);    }
    // Hitting test    for (int i = 0; i < 1000'000; i++)    {        string dataKey = to_string(random());        string nodeKey = hashRing.getNode(dataKey);
        auto hittedItem = counting.find(nodeKey);        hittedItem->second++;    }
    // Calculate standard deviation    double sum = 0;    for_each(counting.begin(), counting.end(), [&](decltype(counting)::const_reference item) { sum += item.second; });    double mean = sum / counting.size();    double variance = 0.;    for_each(counting.begin(), counting.end(), [&](decltype(counting)::const_reference item) { variance += pow(item.second - mean, 2.); });    variance = variance / counting.size();    double standardDeviation = sqrt(variance);
    // Output results    for (auto &item : counting)    {        cout << item.first << ", hits: " << item.second << endl;    }    cout << "Standard deviation: " << standardDeviation << endl;
    return 0;}

192.168.100.101, hits: 99253192.168.100.102, hits: 90910192.168.100.103, hits: 124879192.168.100.104, hits: 99950192.168.100.105, hits: 108481192.168.100.106, hits: 91469192.168.100.107, hits: 82288192.168.100.108, hits: 102209192.168.100.109, hits: 103421192.168.100.110, hits: 97140Standard deviation: 10887.3