BUG/MINOR: cache: Check cache entry is complete in case of Vary
Before looking for a secondary cache entry for a given request we
checked that the first entry was complete, which might prevent us from
using a valid entry if the first one with the same primary key is not
full yet.
Likewise, if the primary entry is complete but not the secondary entry
we try to use, we might end up using a partial entry from the cache as
a response.
This bug was raised in GitHub #2048.
It can be backported up to branch 2.4.
diff --git a/src/cache.c b/src/cache.c
index c7a231b..9683c08 100644
--- a/src/cache.c
+++ b/src/cache.c
@@ -1802,8 +1802,10 @@
shctx_lock(shctx_ptr(cache));
res = entry_exist(cache, s->txn->cache_hash);
- /* We must not use an entry that is not complete. */
- if (res && res->complete) {
+ /* We must not use an entry that is not complete but the check will be
+ * performed after we look for a potential secondary entry (in case of
+ * Vary). */
+ if (res) {
struct appctx *appctx;
entry_block = block_ptr(res);
shctx_row_inc_hot(shctx_ptr(cache), entry_block);
@@ -1830,9 +1832,11 @@
res = NULL;
}
- /* We looked for a valid secondary entry and could not find one,
- * the request must be forwarded to the server. */
- if (!res) {
+ /* We either looked for a valid secondary entry and could not
+ * find one, or the entry we want to use is not complete. We
+ * can't use the cache's entry and must forward the request to
+ * the server. */
+ if (!res || !res->complete) {
shctx_lock(shctx_ptr(cache));
shctx_row_dec_hot(shctx_ptr(cache), entry_block);
shctx_unlock(shctx_ptr(cache));