[nginx] SSL: reduced logging of session cache failures (ticket #621).

[Sergey Kandaurov]

details:   https://hg.nginx.org/nginx/rev/38c71f9b2293
branches:  
changeset: 8075:38c71f9b2293
user:      Maxim Dounin <mdounin at mdounin.ru>
date:      Wed Oct 12 20:14:36 2022 +0300
description:
SSL: reduced logging of session cache failures (ticket #621).

Session cache allocations might fail as long as the new session is different
in size from the one least recently used (and freed when the first allocation
fails).  In particular, it might not be possible to allocate space for
sessions with client certificates, since they are noticeably bigger than
normal sessions.

To ensure such allocation failures won't clutter logs, logging level changed
to "warn", and logging is now limited to at most one warning per second.

diffstat:

 src/event/ngx_event_openssl.c |  9 +++++++--
 src/event/ngx_event_openssl.h |  1 +
 2 files changed, 8 insertions(+), 2 deletions(-)

diffs (37 lines):

diff -r 026ee23b6774 -r 38c71f9b2293 src/event/ngx_event_openssl.c
--- a/src/event/ngx_event_openssl.c	Wed Oct 12 20:14:34 2022 +0300
+++ b/src/event/ngx_event_openssl.c	Wed Oct 12 20:14:36 2022 +0300
@@ -3770,6 +3770,8 @@ ngx_ssl_session_cache_init(ngx_shm_zone_
 
     ngx_queue_init(&cache->expire_queue);
 
+    cache->fail_time = 0;
+
     len = sizeof(" in SSL session shared cache \"\"") + shm_zone->shm.name.len;
 
     shpool->log_ctx = ngx_slab_alloc(shpool, len);
@@ -3953,8 +3955,11 @@ failed:
 
     ngx_shmtx_unlock(&shpool->mutex);
 
-    ngx_log_error(NGX_LOG_ALERT, c->log, 0,
-                  "could not allocate new session%s", shpool->log_ctx);
+    if (cache->fail_time != ngx_time()) {
+        cache->fail_time = ngx_time();
+        ngx_log_error(NGX_LOG_WARN, c->log, 0,
+                      "could not allocate new session%s", shpool->log_ctx);
+    }
 
     return 0;
 }
diff -r 026ee23b6774 -r 38c71f9b2293 src/event/ngx_event_openssl.h
--- a/src/event/ngx_event_openssl.h	Wed Oct 12 20:14:34 2022 +0300
+++ b/src/event/ngx_event_openssl.h	Wed Oct 12 20:14:36 2022 +0300
@@ -150,6 +150,7 @@ typedef struct {
     ngx_rbtree_t                session_rbtree;
     ngx_rbtree_node_t           sentinel;
     ngx_queue_t                 expire_queue;
+    time_t                      fail_time;
 } ngx_ssl_session_cache_t;