sql_cacher: don't allow usage of a replicated local cache

Using a replicated collection for cachedb_local would lead to invalid
keys in the cache due to reload version inconsistencies.

(cherry picked from commit 1b96626)

cachedb/cachedb.h

@@ -144,6 +144,11 @@ typedef struct cachedb_funcs_t {
 	               const cdb_dict_t *pairs);
 	/* TODO: can we also implement these ^ with Redis, or can we adapt them? */
 
+	/* Checks if the database is replicated (in an OpenSIPS cluster).
+	 * Currently only makes sense for cachedb_local
+	 */
+	int (*is_replicated) (cachedb_con *con);
+
 	int capability;
 } cachedb_funcs;
 

modules/cachedb_local/cachedb_local.c

@@ -321,6 +321,10 @@ void lcache_destroy(cachedb_con *con)
 	cachedb_do_close(con,lcache_free_connection);
 }
 
+int lcache_is_replicated (cachedb_con *con)
+{
+	return cluster_id ? 1 : 0;
+}
 
 /**
  * init module function
@@ -348,6 +352,7 @@ static int mod_init(void)
 	cde.cdb_func.remove = lcache_htable_remove;
 	cde.cdb_func.add = lcache_htable_add;
 	cde.cdb_func.sub = lcache_htable_sub;
+	cde.cdb_func.is_replicated = lcache_is_replicated;
 
 	cde.cdb_func.capability = CACHEDB_CAP_BINARY_VALUE;
 

modules/sql_cacher/sql_cacher.c

@@ -743,6 +743,13 @@ static db_handlers_t *db_init_test_conn(cache_entry_t *c_entry)
 			c_entry->cachedb_url.len, c_entry->cachedb_url.s);
 		return NULL;
 	}
+
+	if (new_db_hdls->cdbf.is_replicated &&
+		new_db_hdls->cdbf.is_replicated(new_db_hdls->cdbcon)) {
+		LM_ERR("Cannot use an OpenSIPS replicated cacheDB\n");
+		return NULL;
+	}
+
 	/* setting and getting a test key in cachedb */
 	if (new_db_hdls->cdbf.set(new_db_hdls->cdbcon, &cdb_test_key, &cdb_test_val,
 		0) < 0) {