Make tail leak expiry time configurable

3 files changed, 18 insertions, 3 deletions

diff --git a/items.c b/items.c
index 85fd7e1..d70400c 100644
--- a/items.c
+++ b/items.c
@@ -125,7 +125,7 @@ item *do_item_alloc(char *key, const size_t nkey, const int flags,
             /* Old rare bug could cause a refcount leak. We haven't seen
              * it in years, but we leave this code in to prevent failures
              * just in case */
-            if (search->time + TAIL_REPAIR_TIME < current_time) {
+            if (search->time + settings.tail_repair_time < current_time) {
                 itemstats[id].tailrepairs++;
                 search->refcount = 1;
                 do_item_unlink_nolock(search, hv);
diff --git a/memcached.c b/memcached.c
index f3b9939..cc89a12 100644
--- a/memcached.c
+++ b/memcached.c
@@ -226,6 +226,7 @@ static void settings_init(void) {
     settings.slab_reassign = false;
     settings.slab_automove = 0;
     settings.shutdown_command = false;
+    settings.tail_repair_time = TAIL_REPAIR_TIME_DEFAULT;
 }
 
 /*
@@ -2624,6 +2625,7 @@ static void process_stat_settings(ADD_STAT add_stats, void *c) {
     APPEND_STAT("hashpower_init", "%d", settings.hashpower_init);
     APPEND_STAT("slab_reassign", "%s", settings.slab_reassign ? "yes" : "no");
     APPEND_STAT("slab_automove", "%d", settings.slab_automove);
+    APPEND_STAT("tail_repair_time", "%d", settings.tail_repair_time);
 }
 
 static void process_stat(conn *c, token_t *tokens, const size_t ntokens) {
@@ -4523,6 +4525,9 @@ static void usage(void) {
            "                table should be. Can be grown at runtime if not big enough.\n"
            "                Set this based on \"STAT hash_power_level\" before a \n"
            "                restart.\n"
+           "              - tail_repair_time: Time in seconds that indicates how long to wait before\n"
+           "                forcefully taking over the LRU tail item whose refcount has leaked.\n"
+           "                The default is 3 hours.\n"
            );
     return;
 }
@@ -4757,13 +4762,15 @@ int main (int argc, char **argv) {
         MAXCONNS_FAST = 0,
         HASHPOWER_INIT,
         SLAB_REASSIGN,
-        SLAB_AUTOMOVE
+        SLAB_AUTOMOVE,
+        TAIL_REPAIR_TIME
     };
     char *const subopts_tokens[] = {
         [MAXCONNS_FAST] = "maxconns_fast",
         [HASHPOWER_INIT] = "hashpower",
         [SLAB_REASSIGN] = "slab_reassign",
         [SLAB_AUTOMOVE] = "slab_automove",
+        [TAIL_REPAIR_TIME] = "tail_repair_time",
         NULL
     };
 
@@ -5033,6 +5040,13 @@ int main (int argc, char **argv) {
                     return 1;
                 }
                 break;
+            case TAIL_REPAIR_TIME:
+                if (subopts_value == NULL) {
+                    fprintf(stderr, "Missing numeric argument for tail_repair_time\n");
+                    return 1;
+                }
+                settings.tail_repair_time = atoi(subopts_value);
+                break;
             default:
                 printf("Illegal suboption \"%s\"\n", subopts_value);
                 return 1;
diff --git a/memcached.h b/memcached.h
index 91b6502..9308db9 100644
--- a/memcached.h
+++ b/memcached.h
@@ -76,7 +76,7 @@
 
 /** How long an object can reasonably be assumed to be locked before
     harvesting it on a low memory condition. */
-#define TAIL_REPAIR_TIME (3 * 3600)
+#define TAIL_REPAIR_TIME_DEFAULT (3 * 3600)
 
 /* warning: don't use these macros with a function, as it evals its arg twice */
 #define ITEM_get_cas(i) (((i)->it_flags & ITEM_CAS) ? \
@@ -308,6 +308,7 @@ struct settings {
     int slab_automove;     /* Whether or not to automatically move slabs */
     int hashpower_init;     /* Starting hash power level */
     bool shutdown_command; /* allow shutdown command */
+    int tail_repair_time;   /* LRU tail refcount leak repair time */
 };
 
 extern struct stats stats;