[discuss]: support use native Lua coroutine in `init_worker` phase

[tzssangglass]

According to the documentation here: https://github.com/openresty/lua-nginx-module#coroutinecreate

coroutine.create can be used in init_by_lua*, header_filter_by_lua*, body_filter_by_lua*, because OpenResty would replace OpenResty's coroutine with the Lua native coroutine in these phases, which can not yield.

code:

lua-nginx-module/src/ngx_http_lua_coroutine.c

Lines 336 to 375 in d34d3c5

	{
	const char buf[] =
	"local keys = {'create', 'yield', 'resume', 'status', 'wrap'}\n"
	#ifdef OPENRESTY_LUAJIT
	"local get_req = require 'thread.exdata'\n"
	#else
	"local getfenv = getfenv\n"
	#endif
	"for _, key in ipairs(keys) do\n"
	"local std = coroutine['_' .. key]\n"
	"local ours = coroutine['__' .. key]\n"
	"local raw_ctx = ngx._phase_ctx\n"
	"coroutine[key] = function (...)\n"
	#ifdef OPENRESTY_LUAJIT
	"local r = get_req()\n"
	#else
	"local r = getfenv(0).__ngx_req\n"
	#endif
	"if r ~= nil then\n"
	#ifdef OPENRESTY_LUAJIT
	"local ctx = raw_ctx()\n"
	#else
	"local ctx = raw_ctx(r)\n"
	#endif
	/* ignore header and body filters */
	"if ctx ~= 0x020 and ctx ~= 0x040 then\n"
	"return ours(...)\n"
	"end\n"
	"end\n"
	"return std(...)\n"
	"end\n"
	"end\n"
	"package.loaded.coroutine = coroutine"
	#if 0
	"debug.sethook(function () collectgarbage() end, 'rl', 1)"
	#endif
	;
	rc = luaL_loadbuffer(L, buf, sizeof(buf) - 1, "=coroutine_api");
	}

And also here: https://github.com/openresty/lua-resty-core/blob/master/lib/resty/core/coroutine.lua#L4-L24

Now the problem is: If I call coroutine.create in init_worker phase, match the

                if ctx ~= 0x020 and ctx ~= 0x040 then
                    return ours(...)
                end

And then return the OpenResty's coroutine. (ctx of init_worker is 0x0100)

This would cause ean rror API disabled in the context of init_worker_by_lua* because check here:

lua-nginx-module/src/ngx_http_lua_coroutine.c

Line 117 in d34d3c5

ngx_http_lua_check_context(L, ctx, NGX_HTTP_LUA_CONTEXT_YIELDABLE);

So I suggest returning the Lua native coroutine in the init_worker phase, change like

                if ctx ~= 0x020 and ctx ~= 0x040 and ctx ~= 0x0100 then
                    return ours(...)
                end

This may allow users to use native Lua coroutine in init_worker phase.

[tzssangglass]

ping @zhuizhuhaomeng

[oowl]

FYI, we have the cosocket impl PR in the init_worker phase before #1825

[tzssangglass]

In this case, we don't need a cosocket in the init_worker phase; instead, we allow users to use native Lua coroutines in this phase.