瓦片处理磁盘缓存

2026-07-16 10:06:01 +08:00
parent fb57d51ee5
commit 74c6e3981d
4 changed files with 163 additions and 14 deletions
@@ -0,0 +1,161 @@
+#include "Global.h"
+#include "Performance_Monitor.h"
+#include <cstdint>
+#include <ctime>
+#include <filesystem>
+#include <format>
+#include <optional>
+#include <string>
+#include <string_view>
+#include <sys/stat.h>
+/**
+ * 瓦片文件缓存策略：
+ *  * 首次请求通过 newFileResponse() 直接发送文件，避免先把整个文件读取到内存。
+ *  * 根据文件修改时间和大小生成弱 ETag，同时返回 Last-Modified。
+ *  * 浏览器缓存未过期时直接使用本地缓存，不再请求服务器。
+ *  * 缓存过期或强制刷新时，浏览器自动携带 If-None-Match 或 If-Modified-Since。
+ *  * 服务端优先验证 If-None-Match，文件未变化时返回 304，不重复传输文件内容。
+ *  * 404 响应使用 no-store，避免不存在的瓦片被浏览器长期缓存。
+ *  * max-age=31536000, immutable 仅适用于同一 URL 对应的文件永远不被原地修改；
+ *    如果瓦片可能在原路径更新，应移除 immutable 并使用较短的 max-age。
+ */
+namespace {
+struct File_Cache_Info {
+    std::uint64_t size;
+    std::time_t modified_time;
+    std::string etag;
+    std::string last_modified;
+};
+std::string format_http_date(std::time_t time) {
+    std::tm tm{};
+#ifdef _WIN32
+    gmtime_s(&tm, &time);
+#else
+    gmtime_r(&time, &tm);
+#endif
+    char buffer[64];
+    auto size = std::strftime(buffer, sizeof(buffer), "%a, %d %b %Y %H:%M:%S GMT", &tm);
+    return std::string(buffer, size);
+}
+std::optional<File_Cache_Info> get_file_cache_info(const std::string& path) {
+    auto native_path = std::filesystem::path(path);
+#ifdef _WIN32
+    struct _stati64 info{};
+    if (_wstati64(native_path.c_str(), &info) != 0 || (info.st_mode & _S_IFMT) != _S_IFREG) {
+        return std::nullopt;
+    }
+#else
+    struct stat info{};
+    if (::stat(native_path.c_str(), &info) != 0 || !S_ISREG(info.st_mode)) {
+        return std::nullopt;
+    }
+#endif
+    File_Cache_Info result;
+    result.size = static_cast<std::uint64_t>(info.st_size);
+    result.modified_time = info.st_mtime;
+    result.etag = std::format(
+        "W/\"{:x}-{:x}\"",
+        static_cast<std::uint64_t>(result.modified_time),
+        result.size);
+    result.last_modified = format_http_date(result.modified_time);
+    return result;
+}
+std::string_view trim_http_ows(std::string_view value) {
+    while (!value.empty() && (value.front() == ' ' || value.front() == '\t')) {
+        value.remove_prefix(1);
+    }
+    while (!value.empty() && (value.back() == ' ' || value.back() == '\t')) {
+        value.remove_suffix(1);
+    }
+    return value;
+}
+std::string_view remove_weak_prefix(std::string_view etag) {
+    if (etag.starts_with("W/")) {
+        etag.remove_prefix(2);
+    }
+    return etag;
+}
+bool etag_matches(std::string_view values, std::string_view current_etag) {
+    while (!values.empty()) {
+        auto pos = values.find(',');
+        auto value = trim_http_ows(values.substr(0, pos));
+        if (value == "*" || remove_weak_prefix(value) == remove_weak_prefix(current_etag)) {
+            return true;
+        }
+        if (pos == std::string_view::npos) {
+            break;
+        }
+        values.remove_prefix(pos + 1);
+    }
+    return false;
+}
+void add_tile_cache_headers(
+    const drogon::HttpResponsePtr& response,
+    const File_Cache_Info& info) {
+    response->addHeader("Cache-Control", "public, max-age=86400");
+    //response->addHeader("Cache-Control", "public, max-age=31536000, immutable");
+    response->addHeader("ETag", info.etag);
+    response->addHeader("Last-Modified", info.last_modified);
+}
+drogon::HttpResponsePtr make_tile_not_found_response(const std::string& path) {
+    auto response = drogon::HttpResponse::newHttpResponse();
+    JSON ret = JSON::object();
+    ret.append({"LOG_POS", LOG_POS});
+    ret.append({"not_found_path", path});
+    response->setStatusCode(drogon::k404NotFound);
+    response->setContentTypeCode(drogon::CT_TEXT_PLAIN);
+    response->setBody(ret.to_json_string());
+    response->addHeader("Cache-Control", "no-store");
+    return response;
+}
+drogon::HttpResponsePtr return_tile_file(
+    const drogon::HttpRequestPtr& req,
+    const std::string& path) {
+    auto info = get_file_cache_info(path);
+    if (!info) {
+        return make_tile_not_found_response(path);
+    }
+    const auto& if_none_match = req->getHeader("if-none-match");
+    bool not_modified;
+    if (!if_none_match.empty()) {
+        not_modified = etag_matches(if_none_match, info->etag);
+    }
+    else {
+        const auto& if_modified_since = req->getHeader("if-modified-since");
+        not_modified = !if_modified_since.empty() && if_modified_since == info->last_modified;
+    }
+    if (not_modified) {
+        auto response = drogon::HttpResponse::newHttpResponse();
+        response->setStatusCode(drogon::k304NotModified);
+        response->setContentTypeCode(drogon::CT_NONE);
+        add_tile_cache_headers(response, *info);
+        return response;
+    }
+    auto content_type = httplib::detail::find_content_type(
+        path,
+        {},
+        "application/octet-stream");
+    auto response = drogon::HttpResponse::newFileResponse(
+        path,
+        "",
+        drogon::CT_CUSTOM,
+        content_type,
+        req);
+    if (response->statusCode() == drogon::k200OK ||
+        response->statusCode() == drogon::k206PartialContent) {
+        add_tile_cache_headers(response, *info);
+    }
+    return response;
+}
+}
+void Global::init_tiles() {
+    static auto& web_server = web_server_config;
+    drogon::app().registerHandlerViaRegex(
+        R"(^/tiles/.*$)",
+        [](const drogon::HttpRequestPtr& req,
+           std::function<void(const drogon::HttpResponsePtr&)>&& callback) {
+            auto path = web_server.get_true_tiles() + req->getPath().substr(6);
+            callback(return_tile_file(req, path));
+        },
+        {drogon::Get});
+}