feature: applied the intercept_error_log patch to the nginx core to provide 3rd-party modules a hook to intercept nginx error log data without touching files.

3rd-party modules can register a custom interception hook to ngx_http_core_main_conf_t.intercept_log_handler.

Signed-off-by: Yichun Zhang (agentzh) <agentzh@gmail.com>

patches/nginx-1.11.2-intercept_error_log.patch

@@ -0,0 +1,60 @@
+diff --git a/src/core/ngx_cycle.h b/src/core/ngx_cycle.h
+index c51b7ff..4c335b9 100644
+--- a/src/core/ngx_cycle.h
++++ b/src/core/ngx_cycle.h
+@@ -22,9 +22,14 @@
+ #define NGX_DEBUG_POINTS_ABORT  2
+ 
+ 
++#define HAVE_INTERCEPT_ERROR_LOG_PATCH
++
++
+ typedef struct ngx_shm_zone_s  ngx_shm_zone_t;
+ 
+ typedef ngx_int_t (*ngx_shm_zone_init_pt) (ngx_shm_zone_t *zone, void *data);
++typedef ngx_int_t (*ngx_log_intercept_pt) (ngx_log_t *log, ngx_uint_t level,
++    u_char *buf, size_t len);
+ 
+ struct ngx_shm_zone_s {
+     void                     *data;
+@@ -75,6 +80,10 @@ struct ngx_cycle_s {
+     ngx_str_t                 prefix;
+     ngx_str_t                 lock_file;
+     ngx_str_t                 hostname;
++
++    ngx_log_intercept_pt      intercept_error_log_handler;
++    void                     *intercept_error_log_data;
++    unsigned                  entered_logger;    /* :1 */
+ };
+ 
+ 
+diff --git a/src/core/ngx_log.c b/src/core/ngx_log.c
+index 8e9408d..ed9b11b 100644
+--- a/src/core/ngx_log.c
++++ b/src/core/ngx_log.c
+@@ -112,6 +112,8 @@ ngx_log_error_core(ngx_uint_t level, ngx_log_t *log, ngx_err_t err,
+     ngx_uint_t   wrote_stderr, debug_connection;
+     u_char       errstr[NGX_MAX_ERROR_STR];
+ 
++    ngx_log_intercept_pt    log_intercept = NULL;
++
+     last = errstr + NGX_MAX_ERROR_STR;
+ 
+     p = ngx_cpymem(errstr, ngx_cached_err_log_time.data,
+@@ -153,6 +155,16 @@ ngx_log_error_core(ngx_uint_t level, ngx_log_t *log, ngx_err_t err,
+         p = last - NGX_LINEFEED_SIZE;
+     }
+ 
++    if (ngx_cycle) {
++        log_intercept = ngx_cycle->intercept_error_log_handler;
++    }
++
++    if (log_intercept && !ngx_cycle->entered_logger) {
++        ngx_cycle->entered_logger = 1;
++        log_intercept(log, level, errstr, p - errstr);
++        ngx_cycle->entered_logger = 0;
++    }
++
+     ngx_linefeed(p);
+ 
+     wrote_stderr = 0;

util/mirror-tarballs

@@ -55,9 +55,19 @@ else
     fi
 fi
 
-echo "$info_txt applying the privileged-agent-process patch"
-patch -p1 < $root/patches/nginx-$main_ver-privileged_agent_process.patch || exit 1
-echo
+answer=`$root/util/ver-ge "$main_ver" 1.11.2`
+if [ "$answer" = "Y" ]; then
+    echo "$info_txt applying the privileged-agent-process patch"
+    patch -p1 < $root/patches/nginx-$main_ver-privileged_agent_process.patch || exit 1
+    echo
+fi
+
+answer=`$root/util/ver-ge "$main_ver" 1.11.2`
+if [ "$answer" = "Y" ]; then
+    echo "$info_txt applying the intercept-error-log patch"
+    patch -p1 < $root/patches/nginx-$main_ver-intercept_error_log.patch || exit 1
+    echo
+fi
 
 echo "$info_txt applying the upstream-pipelining patch for nginx"
 patch -p1 < $root/patches/nginx-$main_ver-upstream_pipelining.patch || exit 1