perf: less nest in filesystem iteration When CleanOldLogFiles::Run

[fxliang]

Pull request

Issue tracker

Fixes will automatically close the related issue

Fixes #

Feature

Describe feature of pull request

less nest when filesystem iteration in CleanOldLogFiles::Run(Deployer* deplyer) for better performance. esp under Windows with log dir %TEMP% and too much files inside that directory.

Unit test

• Done

Manual test

• Done

Code Review

1. Unit and manual test pass
2. GitHub Action CI pass
3. At least one contributor reviews and votes
4. Can be merged clean without conflicts
5. PR will be merged by rebase upstream base

Additional Info

simple test code, target iteration folder ./files with 1 million files. compiled with command
g++ -Wall iterator.cpp -std=c++17 -o iterator

#include <chrono>
#include <iostream>
#include <filesystem>
#include <vector>

using namespace std;
namespace fs = std::filesystem;

int main()
{
    auto start = chrono::high_resolution_clock::now();
    vector<string> dirs;
    // with 1 million files inside ./files
    dirs.push_back("./files");
    // ----------------------------------------------------------------
    vector<string> files;
    for (const auto& dir : dirs) {
        for (const auto& entry : fs::directory_iterator(dir)){
            if(entry.is_regular_file() && !entry.is_symlink())
                files.push_back(entry.path().string());
        }
    }
    for (const auto& file: files) {
    }
    vector<string>().swap(files);
    auto _end = chrono::high_resolution_clock::now();
    auto duration = chrono::duration_cast<chrono::microseconds>(_end - start);
    cout << "with new process, duration: " << duration.count() << " us" << endl;

    // ----------------------------------------------------------------
    start = chrono::high_resolution_clock::now();
    for (auto i = dirs.cbegin(); i != dirs.cend(); ++i) {
        for (fs::directory_iterator j(*i), end; j != end; ++j) {
            fs::path entry(j->path());
            string file_name(entry.filename().string());
            if (fs::is_regular_file(entry) && !fs::is_symlink(entry));
        }
    }
    _end = chrono::high_resolution_clock::now();
    duration = chrono::duration_cast<chrono::microseconds>(_end - start);
    cout << "with old process, duration: " << duration.count() << " us" << endl;
    return 0;
}