Cache: ignore stale-if-error for 4xx and 5xx codes. Previously the stale-if-error extension of the Cache-Control upstream header triggered the return of a stale response for all error conditions that can be specified in the proxy_cache_use_stale directive. The list of these errors includes both network/timeout/format errors, as well as some HTTP codes like 503, 504, 403, 429 etc. The latter prevented a cache entry from being updated by a response with any of these HTTP codes during the stale-if-error period. Now stale-if-error only works for network/timeout/format errors and ignores the upstream HTTP code. The return of a stale response for certain HTTP codes is still possible using the proxy_cache_use_stale directive. This change also applies to the stale-while-revalidate extension of the Cache-Control header, which triggers stale-if-error if it is missing. Reported at http://mailman.nginx.org/pipermail/nginx/2020-July/059723.html.

/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 */


#ifndef _NGX_PROCESS_CYCLE_H_INCLUDED_
#define _NGX_PROCESS_CYCLE_H_INCLUDED_


#include <ngx_config.h>
#include <ngx_core.h>


#define NGX_PROCESS_SINGLE     0
#define NGX_PROCESS_MASTER     1
#define NGX_PROCESS_SIGNALLER  2
#define NGX_PROCESS_WORKER     3


void ngx_master_process_cycle(ngx_cycle_t *cycle);
void ngx_single_process_cycle(ngx_cycle_t *cycle);
void ngx_close_handle(HANDLE h);


extern ngx_uint_t      ngx_process;
extern ngx_uint_t      ngx_worker;
extern ngx_pid_t       ngx_pid;
extern ngx_uint_t      ngx_exiting;

extern sig_atomic_t    ngx_quit;
extern sig_atomic_t    ngx_terminate;
extern sig_atomic_t    ngx_reopen;

extern ngx_uint_t      ngx_inherited;
extern ngx_pid_t       ngx_new_binary;


extern HANDLE          ngx_master_process_event;
extern char            ngx_master_process_event_name[];


#endif /* _NGX_PROCESS_CYCLE_H_INCLUDED_ */