Configurable read buffer size

src/main.cpp

@@ -161,13 +161,12 @@ struct Connection {
   // response
   bool closeConnection{false};
 
-  bool readBytes(size_t max_request_size) {
-    // Use smaller buffer size but respect max request size
-    // TODO revisit
-    size_t buf_size = std::min(size_t(4096), max_request_size);
-    std::vector<char> buf(buf_size);
+  bool readBytes(size_t max_request_size, size_t buffer_size) {
+    // Use Variable Length Array for optimal stack allocation
+    char buf[buffer_size];
+
     for (;;) {
-      int r = read(fd, buf.data(), buf.size());
+      int r = read(fd, buf, buffer_size);
       if (r == -1) {
         if (errno == EINTR) {
           continue;
@@ -183,7 +182,7 @@ struct Connection {
       }
       // "pump parser"
       // TODO revisit
-      appendMessage({buf.data(), size_t(r)});
+      appendMessage({buf, size_t(r)});
     }
   }
 
@@ -261,11 +260,53 @@ struct Connection {
 #endif
 };
 
+void print_help(const char *program_name) {
+  std::cout << "WeaselDB - High-performance write-side database component\n\n";
+  std::cout << "Usage: " << program_name << " [OPTIONS]\n\n";
+  std::cout << "Options:\n";
+  std::cout << "  --config <file>    Path to TOML configuration file (default: "
+               "config.toml)\n";
+  std::cout << "  --help             Show this help message and exit\n";
+  std::cout << "  -h                 Show this help message and exit\n\n";
+  std::cout << "Examples:\n";
+  std::cout << "  " << program_name
+            << "                    # Use default config.toml\n";
+  std::cout << "  " << program_name
+            << " --config my.toml   # Use custom config file\n";
+  std::cout << "  " << program_name
+            << " --help             # Show this help\n\n";
+  std::cout << "For configuration documentation, see config.md\n";
+}
+
 int main(int argc, char *argv[]) {
   std::string config_file = "config.toml";
 
-  if (argc > 1) {
-    config_file = argv[1];
+  // Parse command line arguments
+  for (int i = 1; i < argc; i++) {
+    std::string arg = argv[i];
+
+    if (arg == "--help" || arg == "-h") {
+      print_help(argv[0]);
+      return 0;
+    } else if (arg == "--config") {
+      if (i + 1 >= argc) {
+        std::cerr << "Error: --config requires a filename argument\n";
+        print_help(argv[0]);
+        return 1;
+      }
+      config_file = argv[++i];
+    } else if (arg.starts_with("--config=")) {
+      config_file = arg.substr(9);
+    } else {
+      // For backward compatibility, treat lone argument as config file
+      if (argc == 2) {
+        config_file = arg;
+      } else {
+        std::cerr << "Error: Unknown argument '" << arg << "'\n";
+        print_help(argv[0]);
+        return 1;
+      }
+    }
   }
 
   auto config = weaseldb::ConfigParser::load_from_file(config_file);
@@ -289,6 +330,8 @@ int main(int argc, char *argv[]) {
             << std::endl;
   std::cout << "Max connections: " << config->server.max_connections
             << std::endl;
+  std::cout << "Read buffer size: " << config->server.read_buffer_size
+            << " bytes" << std::endl;
   std::cout << "Min request ID length: " << config->commit.min_request_id_length
             << std::endl;
   std::cout << "Request ID retention: "
@@ -345,6 +388,7 @@ int main(int argc, char *argv[]) {
     threads.emplace_back(
         [network_epollfd, networkThreadId,
          max_request_size = config->server.max_request_size_bytes,
+         read_buffer_size = config->server.read_buffer_size,
          event_batch_size = config->server.event_batch_size]() {
           pthread_setname_np(
               pthread_self(),
@@ -388,7 +432,7 @@ int main(int argc, char *argv[]) {
                        (events[i].events & EPOLLOUT)));
 
               if (events[i].events & EPOLLIN) {
-                bool done = conn->readBytes(max_request_size);
+                bool done = conn->readBytes(max_request_size, read_buffer_size);
                 if (done) {
                   continue;
                 }