[PATCH] Ensured SIGQUIT deletes listening UNIX socket files.

[Ruslan Ermilov]

Hi there,

On Mon, Apr 27, 2020 at 04:26:31PM -0700, Thibault Charbonnier wrote:
> On 4/25/20 6:12 PM, Maxim Dounin wrote:
> > A better approach might be to check parent's pid instead, much 
> > like we do when handling the changebin signal on unix (see 
> > src/os/unix/ngx_process.c).
> 
> Great! Thanks for the suggestion. Below is a revised approach for the
> patch (also attached to this email) which passes all of the test cases
> listed in my previous test file at the start of this thread:
> 
> # HG changeset patch
> # User Thibault Charbonnier <thibaultcha at me.com>
> # Date 1582764433 28800
> #      Wed Feb 26 16:47:13 2020 -0800
> # Node ID 8d781bac6c4feebb2d1ea3f4e6df76d71f74e43b
> # Parent  4f18393a1d51bce6103ea2f1b2587900f349ba3d
> Ensured SIGQUIT deletes listening UNIX socket files.
> 
> Prior to this patch, the SIGQUIT signal handling (graceful shutdown) did not
> remove UNIX socket files since ngx_master_process_cycle reimplemented listening
> socket closings in lieu of using ngx_close_listening_sockets.
> 
> Since ngx_master_process_exit will call the aforementioned
> ngx_close_listening_sockets, we can remove the custom implementation and now
> expect listening sockets to be closed properly by ngx_close_listening_sockets
> instead.
> 
> This fixes the trac issue #753 (https://trac.nginx.org/nginx/ticket/753).
> 
> diff -r 4f18393a1d51 -r 8d781bac6c4f src/core/ngx_connection.c
> --- a/src/core/ngx_connection.c	Thu Feb 20 16:51:07 2020 +0300
> +++ b/src/core/ngx_connection.c	Wed Feb 26 16:47:13 2020 -0800
> @@ -1070,7 +1070,8 @@
>  
>          if (ls[i].sockaddr->sa_family == AF_UNIX
>              && ngx_process <= NGX_PROCESS_MASTER
> -            && ngx_new_binary == 0)
> +            && ngx_new_binary == 0
> +            && ngx_getppid() != ngx_parent)
>          {
>              u_char *name = ls[i].addr_text.data + sizeof("unix:") - 1;
>  
> diff -r 4f18393a1d51 -r 8d781bac6c4f src/os/unix/ngx_process_cycle.c
> --- a/src/os/unix/ngx_process_cycle.c	Thu Feb 20 16:51:07 2020 +0300
> +++ b/src/os/unix/ngx_process_cycle.c	Wed Feb 26 16:47:13 2020 -0800
> @@ -77,12 +77,11 @@
>      u_char            *p;
>      size_t             size;
>      ngx_int_t          i;
> -    ngx_uint_t         n, sigio;
> +    ngx_uint_t         sigio;
>      sigset_t           set;
>      struct itimerval   itv;
>      ngx_uint_t         live;
>      ngx_msec_t         delay;
> -    ngx_listening_t   *ls;
>      ngx_core_conf_t   *ccf;
>  
>      sigemptyset(&set);
> @@ -205,16 +204,6 @@
>              ngx_signal_worker_processes(cycle,
>                                          ngx_signal_value(NGX_SHUTDOWN_SIGNAL));
>  
> -            ls = cycle->listening.elts;
> -            for (n = 0; n < cycle->listening.nelts; n++) {
> -                if (ngx_close_socket(ls[n].fd) == -1) {
> -                    ngx_log_error(NGX_LOG_EMERG, cycle->log, ngx_socket_errno,
> -                                  ngx_close_socket_n " %V failed",
> -                                  &ls[n].addr_text);
> -                }
> -            }
> -            cycle->listening.nelts = 0;
> -
>              continue;
>          }
>  

Thanks for your patch.

Unfortunately, it would break removing of UNIX-domain socket files
when nginx is run with "daemon off".

It'd also add a regression that the master process will not remove
the UNIX-domain socket files until after all worker processes have
exited (this has been fixed in 0.1.40).

The committed fixes:
http://hg.nginx.org/nginx/rev/9c038f5e0464
http://hg.nginx.org/nginx/rev/7cbf6389194b