From ecb83c24c43d85a6b4de043b426c1248d4d97318 Mon Sep 17 00:00:00 2001
From: Thierry Fournier <thierry.fournier@ozon.io>
Date: Sat, 28 Nov 2020 15:49:44 +0100
Subject: [PATCH] MINOR: lua-thread: Add the "thread" core variable

The goal is to allow execution of one main lua state per thread.

This commit introduces this variable in the core. Lua state initialized
by thread will have access to this variable, which reports the executing
thread. 0 indicates the shared thread. Programs which must be executed
only once can check for core.thread <= 1.
---
 doc/lua-api/index.rst | 10 ++++++++++
 src/hlua.c            |  9 ++++++---
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/doc/lua-api/index.rst b/doc/lua-api/index.rst
index adeec112f..b6b9809e8 100644
--- a/doc/lua-api/index.rst
+++ b/doc/lua-api/index.rst
@@ -201,6 +201,16 @@ Core class
   :see: :js:attr:`core.proxies`
   :see: :js:attr:`core.backends`
 
+.. js:attribute:: core.thread
+
+  **context**: task, action, sample-fetch, converter, applet
+
+  This variable contains the executing thread number starting at 1. 0 is a
+  special case for the common lua context. So, if thread is 0, Lua scope is
+  shared by all threads, otherwise the scope is dedicated to a single thread.
+  A program which needs to execute some parts exactly once regardless of the
+  number of threads can check that core.thread is 0 or 1.
+
 .. js:function:: core.log(loglevel, msg)
 
   **context**: body, init, task, action, sample-fetch, converter
diff --git a/src/hlua.c b/src/hlua.c
index 34e7403cf..6153ab769 100644
--- a/src/hlua.c
+++ b/src/hlua.c
@@ -8397,11 +8397,11 @@ static void *hlua_alloc(void *ud, void *ptr, size_t osize, size_t nsize)
 	return ptr;
 }
 
-/* Ithis function can fail with an abort() due to an Lua critical error.
+/* This function can fail with an abort() due to a Lua critical error.
  * We are in the initialisation process of HAProxy, this abort() is
  * tolerated.
  */
-lua_State *hlua_init_state(void)
+lua_State *hlua_init_state(int thread_num)
 {
 	int i;
 	int idx;
@@ -8468,6 +8468,9 @@ lua_State *hlua_init_state(void)
 	/* This table entry is the object "core" base. */
 	lua_newtable(L);
 
+	/* set the thread id */
+	hlua_class_const_int(L, "thread", thread_num);
+
 	/* Push the loglevel constants. */
 	for (i = 0; i < NB_LOG_LEVELS; i++)
 		hlua_class_const_int(L, log_levels[i], i);
@@ -8993,7 +8996,7 @@ lua_State *hlua_init_state(void)
 }
 
 void hlua_init(void) {
-	gL.T = hlua_init_state();
+	gL.T = hlua_init_state(0);
 }
 
 static void hlua_deinit()