Increase soft limit for number of open file descriptors

nano/lib/utility.cpp

@@ -35,11 +35,11 @@
 #include <sys/resource.h>
 #endif
 
-std::size_t nano::get_filedescriptor_limit ()
+std::size_t nano::get_file_descriptor_limit ()
 {
 	std::size_t fd_limit = (std::numeric_limits<std::size_t>::max) ();
 #ifndef _WIN32
-	struct rlimit limit;
+	rlimit limit{};
 	if (getrlimit (RLIMIT_NOFILE, &limit) == 0)
 	{
 		fd_limit = static_cast<std::size_t> (limit.rlim_cur);
@@ -48,6 +48,30 @@ std::size_t nano::get_filedescriptor_limit ()
 	return fd_limit;
 }
 
+void nano::set_file_descriptor_limit (std::size_t limit)
+{
+#ifndef _WIN32
+	rlimit fd_limit{};
+	if (-1 == getrlimit (RLIMIT_NOFILE, &fd_limit))
+	{
+		std::cerr << "Unable to get current limits for the number of open file descriptors: " << std::strerror (errno);
+		return;
+	}
+
+	if (fd_limit.rlim_cur >= limit)
+	{
+		return;
+	}
+
+	fd_limit.rlim_cur = std::min (limit, fd_limit.rlim_max);
+	if (-1 == setrlimit (RLIMIT_NOFILE, &fd_limit))
+	{
+		std::cerr << "Unable to set limits for the number of open file descriptors: " << std::strerror (errno);
+		return;
+	}
+#endif
+}
+
 nano::container_info_composite::container_info_composite (std::string const & name) :
 	name (name)
 {

nano/lib/utility.hpp

@@ -135,12 +135,12 @@ std::string generate_stacktrace ();
 /**
  * Some systems, especially in virtualized environments, may have very low file descriptor limits,
  * causing the node to fail. This function attempts to query the limit and returns the value. If the
- * limit cannot be queried, or running on a Windows system, this returns max-value of size_t.
- * Increasing the limit programatically is highly system-dependent, and the process may lack the
- * required permissions; the node thus merely logs low limits as a potential problem and leaves
- * the system configuration to the user.
+ * limit cannot be queried, or running on a Windows system, this returns max-value of std::size_t.
+ * Increasing the limit programmatically can be done only for the soft limit, the hard one requiring
+ * super user permissions to modify.
  */
-size_t get_filedescriptor_limit ();
+std::size_t get_file_descriptor_limit ();
+void set_file_descriptor_limit (std::size_t limit);
 
 template <typename... T>
 class observer_set final

nano/nano_node/daemon.cpp

@@ -10,7 +10,6 @@
 #include <nano/node/node.hpp>
 #include <nano/node/openclwork.hpp>
 #include <nano/rpc/rpc.hpp>
-#include <nano/secure/working.hpp>
 
 #include <boost/format.hpp>
 
@@ -19,6 +18,8 @@
 namespace
 {
 volatile sig_atomic_t sig_int_or_term = 0;
+
+constexpr std::size_t OPEN_FILE_DESCRIPTORS_LIMIT = 16384;
 }
 
 static void load_and_set_bandwidth_params (std::shared_ptr<nano::node> const & node, boost::filesystem::path const & data_path, nano::node_flags const & flags)
@@ -71,13 +72,8 @@ void nano_daemon::daemon::run (boost::filesystem::path const & data_path, nano::
 			std::cout << initialization_text << std::endl;
 			logger.always_log (initialization_text);
 
-			size_t fd_limit = nano::get_filedescriptor_limit ();
-			constexpr size_t fd_limit_recommended_minimum = 16384;
-			if (fd_limit < fd_limit_recommended_minimum)
-			{
-				auto low_fd_text = boost::str (boost::format ("WARNING: The file descriptor limit on this system may be too low (%1%) and should be increased to at least %2%.") % fd_limit % fd_limit_recommended_minimum);
-				logger.always_log (low_fd_text);
-			}
+			nano::set_file_descriptor_limit (OPEN_FILE_DESCRIPTORS_LIMIT);
+			logger.always_log (boost::format ("Open file descriptors limit is %1%") % nano::get_file_descriptor_limit ());
 
 			auto node (std::make_shared<nano::node> (io_ctx, data_path, config.node, opencl_work, flags));
 			if (!node->init_error ())