Single background thread

nginx.conf

error_log  logs/error.log debug;
events {
    worker_connections  1024;
}

worker_processes 4;

http {
    default_type  application/octet-stream;

    lua_shared_dict test_dict 1m;

    init_by_lua '
        function my_bg_func(premature)
            local dict = ngx.shared["test_dict"]
            local flagged_pid = dict:get("flag")
            local pid = ngx.worker.pid()

            if flagged_pid ~= pid then
                return false
            else
                ngx.log(ngx.DEBUG, "background thread running in ", pid)
                ngx.timer.at(1, my_bg_func)
            end
        end
    ';

    init_worker_by_lua '
        local dict = ngx.shared["test_dict"]

        local ok, err = ngx.timer.at(1, my_bg_func)
        if ok then
            dict:set("flag", ngx.worker.pid())
        else
            ngx.log(ngx.ERR, "Failed to start background thread: "..err)
        end
    ';

}