From 244878483a7fa04f6d7e10b06339f4e9669a6a7b Mon Sep 17 00:00:00 2001
From: Steve Pham <82231385+spham-amzn@users.noreply.github.com>
Date: Thu, 21 Oct 2021 12:40:10 -0700
Subject: [PATCH] Update open file limit on linux for applications (#4878)

* Programmatically update the ulimit for open files if the current limit is not enough

Signed-off-by: Steve Pham <spham@amazon.com>
---
 .../Application/Application_Linux.cpp          | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/Code/Framework/AzFramework/Platform/Linux/AzFramework/Application/Application_Linux.cpp b/Code/Framework/AzFramework/Platform/Linux/AzFramework/Application/Application_Linux.cpp
index 158240210e..85669e093c 100644
--- a/Code/Framework/AzFramework/Platform/Linux/AzFramework/Application/Application_Linux.cpp
+++ b/Code/Framework/AzFramework/Platform/Linux/AzFramework/Application/Application_Linux.cpp
@@ -7,17 +7,35 @@
  */
 
 #include <AzFramework/Application/Application.h>
+#include <sys/resource.h>
 
 #if PAL_TRAIT_LINUX_WINDOW_MANAGER_XCB
 #include <AzFramework/XcbApplication.h>
 #endif
 
+constexpr rlim_t g_minimumOpenFileHandles = 65536L;
+
 ////////////////////////////////////////////////////////////////////////////////////////////////////
 namespace AzFramework
 {
     ////////////////////////////////////////////////////////////////////////////////////////////////
     Application::Implementation* Application::Implementation::Create()
     {
+        // The default open file limit for processes may not be enough for O3DE applications. 
+        // We will need to increase to the recommended value if the current open file limit
+        // is not sufficient.
+        rlimit currentLimit;
+        int get_limit_result = getrlimit(RLIMIT_NOFILE, &currentLimit);
+        AZ_Warning("Application", get_limit_result == 0, "Unable to read current ulimit open file limits");
+        if ((get_limit_result == 0) && (currentLimit.rlim_cur < g_minimumOpenFileHandles || currentLimit.rlim_max < g_minimumOpenFileHandles))
+        {
+            rlimit newLimit;
+            newLimit.rlim_cur = g_minimumOpenFileHandles; // Soft Limit
+            newLimit.rlim_max = g_minimumOpenFileHandles; // Hard Limit
+            [[maybe_unused]] int set_limit_result = setrlimit(RLIMIT_NOFILE, &newLimit);
+            AZ_Assert(set_limit_result == 0, "Unable to update open file limits");
+        }
+        
 #if PAL_TRAIT_LINUX_WINDOW_MANAGER_XCB
         return aznew XcbApplication();
 #elif PAL_TRAIT_LINUX_WINDOW_MANAGER_WAYLAND