Call getMaxFileDescriptorCount once

src/Common/getMaxFileDescriptorCount.cpp

@@ -1,36 +1,19 @@
-#include <IO/ReadHelpers.h>
-#include <IO/WriteBufferFromString.h>
-#include <IO/ReadBufferFromFile.h>
-#include <Common/ShellCommand.h>
 #include <Common/getMaxFileDescriptorCount.h>
-#include <filesystem>
+#include <sys/resource.h>
 
-int getMaxFileDescriptorCount()
+std::optional<size_t> getMaxFileDescriptorCount()
 {
-    namespace fs = std::filesystem;
-    int result = -1;
-#if defined(OS_LINUX) || defined(OS_DARWIN)
-    using namespace DB;
-
-    if (fs::exists("/proc/sys/fs/file-max"))
+    static auto result = []() -> std::optional<size_t>
     {
-        ReadBufferFromFile reader("/proc/sys/fs/file-max");
-        readIntText(result, reader);
-    }
-    else
-    {
-        auto command = ShellCommand::execute("ulimit -n");
-        try
-        {
-            readIntText(result, command->out);
-            command->wait();
-        }
-        catch (...) // NOLINT(bugprone-empty-catch)
-        {
-        }
-    }
-
-#endif
+    #if defined(OS_LINUX) || defined(OS_DARWIN)
+        rlimit rlim;
+        if (getrlimit(RLIMIT_NOFILE, &rlim))
+            return std::nullopt;
+        return rlim.rlim_max;
+    #else
+        return std::nullopt;
+    #endif
+    }();
 
     return result;
 }

src/Common/getMaxFileDescriptorCount.h

@@ -1,6 +1,8 @@
 #pragma once
 
-/// Get process max file descriptor count
-/// @return -1 if os does not support ulimit command or some error occurs
-int getMaxFileDescriptorCount();
+#include <optional>
+
+/// Get process max file descriptor count
+/// @return std::nullopt if os does not support getrlimit command or some error occurs
+std::optional<size_t> getMaxFileDescriptorCount();
 

src/Coordination/FourLetterCommand.cpp

@@ -300,7 +300,11 @@ String MonitorCommand::run()
 
 #if defined(OS_LINUX) || defined(OS_DARWIN)
     print(ret, "open_file_descriptor_count", getCurrentProcessFDCount());
-    print(ret, "max_file_descriptor_count", getMaxFileDescriptorCount());
+    auto max_file_descriptor_count = getMaxFileDescriptorCount();
+    if (max_file_descriptor_count.has_value())
+        print(ret, "max_file_descriptor_count", *max_file_descriptor_count);
+    else
+        print(ret, "max_file_descriptor_count", -1);
 #endif
 
     if (keeper_info.is_leader)

src/Coordination/KeeperAsynchronousMetrics.cpp

@@ -22,7 +22,7 @@ void updateKeeperInformation(KeeperDispatcher & keeper_dispatcher, AsynchronousM
     size_t key_arena_size = 0;
     size_t latest_snapshot_size = 0;
     size_t open_file_descriptor_count = 0;
-    size_t max_file_descriptor_count = 0;
+    std::optional<size_t> max_file_descriptor_count = 0;
     size_t followers = 0;
     size_t synced_followers = 0;
     size_t zxid = 0;
@@ -78,7 +78,10 @@ void updateKeeperInformation(KeeperDispatcher & keeper_dispatcher, AsynchronousM
     new_values["KeeperLatestSnapshotSize"] = { latest_snapshot_size, "The uncompressed size in bytes of the latest snapshot created by ClickHouse Keeper." };
 
     new_values["KeeperOpenFileDescriptorCount"] = { open_file_descriptor_count, "The number of open file descriptors in ClickHouse Keeper." };
-    new_values["KeeperMaxFileDescriptorCount"] = { max_file_descriptor_count, "The maximum number of open file descriptors in ClickHouse Keeper." };
+    if (max_file_descriptor_count.has_value())
+        new_values["KeeperMaxFileDescriptorCount"] = { *max_file_descriptor_count, "The maximum number of open file descriptors in ClickHouse Keeper." };
+    else
+        new_values["KeeperMaxFileDescriptorCount"] = { -1, "The maximum number of open file descriptors in ClickHouse Keeper." };
 
     new_values["KeeperFollowers"] = { followers, "The number of followers of ClickHouse Keeper." };
     new_values["KeeperSyncedFollowers"] = { synced_followers, "The number of followers of ClickHouse Keeper who are also in-sync." };