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Cache: ignore long locked entries during forced expire.

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Abnormally exited workers may leave locked cache entries, this can
result in the cache size on disk exceeding max_size and shared memory
exhaustion.

This change mitigates the issue by ignoring locked entries during forced
expire.  It also increases the visibility of the problem by logging such
entries.
This commit is contained in:
Dmitry Volyntsev 2017-05-18 18:39:16 +03:00
parent 9359155b2f
commit c6df6bf923
1 changed files with 44 additions and 13 deletions
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57
src/http/ngx_http_file_cache.c
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@ -1700,13 +1700,14 @@ ngx_http_file_cache_cleanup(void *data)
static time_t
ngx_http_file_cache_forced_expire(ngx_http_file_cache_t *cache)
{
u_char *name;
u_char *name, *p;
size_t len;
time_t wait;
ngx_uint_t tries;
ngx_path_t *path;
ngx_queue_t *q;
ngx_queue_t *q, *sentinel;
ngx_http_file_cache_node_t *fcn;
u_char key[2 * NGX_HTTP_CACHE_KEY_LEN];
ngx_log_debug0(NGX_LOG_DEBUG_HTTP, ngx_cycle->log, 0,
"http file cache forced expire");
@ -1723,13 +1724,21 @@ ngx_http_file_cache_forced_expire(ngx_http_file_cache_t *cache)
wait = 10;
tries = 20;
sentinel = NULL;
ngx_shmtx_lock(&cache->shpool->mutex);
for (q = ngx_queue_last(&cache->sh->queue);
q != ngx_queue_sentinel(&cache->sh->queue);
q = ngx_queue_prev(q))
{
for ( ;; ) {
if (ngx_queue_empty(&cache->sh->queue)) {
break;
}
q = ngx_queue_last(&cache->sh->queue);
if (q == sentinel) {
break;
}
fcn = ngx_queue_data(q, ngx_http_file_cache_node_t, queue);
ngx_log_debug6(NGX_LOG_DEBUG_HTTP, ngx_cycle->log, 0,
@ -1740,15 +1749,37 @@ ngx_http_file_cache_forced_expire(ngx_http_file_cache_t *cache)
if (fcn->count == 0) {
ngx_http_file_cache_delete(cache, q, name);
wait = 0;
} else {
if (--tries) {
continue;
}
wait = 1;
break;
}
p = ngx_hex_dump(key, (u_char *) &fcn->node.key,
sizeof(ngx_rbtree_key_t));
len = NGX_HTTP_CACHE_KEY_LEN - sizeof(ngx_rbtree_key_t);
(void) ngx_hex_dump(p, fcn->key, len);
/*
* abnormally exited workers may leave locked cache entries,
* and although it may be safe to remove them completely,
* we prefer to just move them to the top of the inactive queue
*/
ngx_queue_remove(q);
fcn->expire = ngx_time() + cache->inactive;
ngx_queue_insert_head(&cache->sh->queue, &fcn->queue);
ngx_log_error(NGX_LOG_ALERT, ngx_cycle->log, 0,
"ignore long locked inactive cache entry %*s, count:%d",
(size_t) 2 * NGX_HTTP_CACHE_KEY_LEN, key, fcn->count);
if (sentinel == NULL) {
sentinel = q;
}
if (--tries) {
continue;
}
wait = 1;
break;
}