[Asterisk-code-review] res sorcery memory cache: Add support for refreshing stale o... (asterisk[certified/13.1])
Mark Michelson
asteriskteam at digium.com
Wed Jul 8 14:37:17 CDT 2015
Mark Michelson has uploaded a new change for review.
https://gerrit.asterisk.org/829
Change subject: res_sorcery_memory_cache: Add support for refreshing stale objects.
......................................................................
res_sorcery_memory_cache: Add support for refreshing stale objects.
This change introduces a check of object_lifetime_stale when retrieving
cached objects. If the amount of time the object has been in the cache
exceeds the lifetime, then a task is scheduled to update the cached
object based on an object retrieved from other sorcery wizards instead.
To prevent the cached object from being retrieved during a refresh,
thread-local storage is used to mark the thread as being a stale object
update. This results in the cache returning no object, leading to
sorcery querying other wizards for the object instead.
A test has been added for stale objects as well. This test ensures that
stale objects are retrieved the same as freshly-cached objects. The test
also ensures that after an object is stale, changes in the backend are
reflected in the cache, to include if the object has been deleted from
the backend.
ASTERISK-25067
Reported by Matt Jordan
Change-Id: I9bd7c049adf6939bfe2899f393c2bfbbf412d217
---
M res/res_sorcery_memory_cache.c
1 file changed, 375 insertions(+), 2 deletions(-)
git pull ssh://gerrit.asterisk.org:29418/asterisk refs/changes/29/829/1
diff --git a/res/res_sorcery_memory_cache.c b/res/res_sorcery_memory_cache.c
index 2bae888..a37ddfd 100644
--- a/res/res_sorcery_memory_cache.c
+++ b/res/res_sorcery_memory_cache.c
@@ -79,6 +79,8 @@
struct timeval created;
/*! \brief index required by heap */
ssize_t __heap_index;
+ /*! \brief scheduler id of stale update task */
+ int stale_update_sched_id;
};
static void *sorcery_memory_cache_open(const char *data);
@@ -116,6 +118,50 @@
/*! \brief Scheduler for cache management */
static struct ast_sched_context *sched;
+
+#define STALE_UPDATE_THREAD_ID 0x5EED1E55
+AST_THREADSTORAGE(stale_update_id_storage);
+
+static int is_stale_update(void)
+{
+ uint32_t *stale_update_thread_id;
+
+ stale_update_thread_id = ast_threadstorage_get(&stale_update_id_storage,
+ sizeof(*stale_update_thread_id));
+ if (!stale_update_thread_id) {
+ return 0;
+ }
+
+ return *stale_update_thread_id == STALE_UPDATE_THREAD_ID;
+}
+
+static void start_stale_update(void)
+{
+ uint32_t *stale_update_thread_id;
+
+ stale_update_thread_id = ast_threadstorage_get(&stale_update_id_storage,
+ sizeof(*stale_update_thread_id));
+ if (!stale_update_thread_id) {
+ ast_log(LOG_ERROR, "Could not set stale update ID for sorcery memory cache thread\n");
+ return;
+ }
+
+ *stale_update_thread_id = STALE_UPDATE_THREAD_ID;
+}
+
+static void end_stale_update(void)
+{
+ uint32_t *stale_update_thread_id;
+
+ stale_update_thread_id = ast_threadstorage_get(&stale_update_id_storage,
+ sizeof(*stale_update_thread_id));
+ if (!stale_update_thread_id) {
+ ast_log(LOG_ERROR, "Could not set stale update ID for sorcery memory cache thread\n");
+ return;
+ }
+
+ *stale_update_thread_id = 0;
+}
/*!
* \internal
@@ -493,13 +539,13 @@
struct sorcery_memory_cache *cache = data;
struct sorcery_memory_cached_object *cached;
- cached = ao2_alloc_options(sizeof(*cached), sorcery_memory_cached_object_destructor,
- AO2_ALLOC_OPT_LOCK_NOLOCK);
+ cached = ao2_alloc(sizeof(*cached), sorcery_memory_cached_object_destructor);
if (!cached) {
return -1;
}
cached->object = ao2_bump(object);
cached->created = ast_tvnow();
+ cached->stale_update_sched_id = -1;
/* As there is no guarantee that this won't be called by multiple threads wanting to cache
* the same object we remove any old ones, which turns this into a create/update function
@@ -531,6 +577,69 @@
return 0;
}
+struct stale_update_task_data {
+ struct ast_sorcery *sorcery;
+ struct sorcery_memory_cache *cache;
+ void *object;
+};
+
+static void stale_update_task_data_destructor(void *obj)
+{
+ struct stale_update_task_data *task_data = obj;
+
+ ao2_cleanup(task_data->cache);
+ ao2_cleanup(task_data->object);
+ ast_sorcery_unref(task_data->sorcery);
+}
+
+static struct stale_update_task_data *stale_update_task_data_alloc(struct ast_sorcery *sorcery,
+ struct sorcery_memory_cache *cache, const char *type, void *object)
+{
+ struct stale_update_task_data *task_data;
+
+ task_data = ao2_alloc_options(sizeof(*task_data), stale_update_task_data_destructor,
+ AO2_ALLOC_OPT_LOCK_NOLOCK);
+ if (!task_data) {
+ return NULL;
+ }
+
+ task_data->sorcery = ao2_bump(sorcery);
+ task_data->cache = ao2_bump(cache);
+ task_data->object = ao2_bump(object);
+
+ return task_data;
+}
+
+static int stale_item_update(const void *data)
+{
+ struct stale_update_task_data *task_data = (struct stale_update_task_data *) data;
+ void *object;
+
+ start_stale_update();
+
+ object = ast_sorcery_retrieve_by_id(task_data->sorcery,
+ ast_sorcery_object_get_type(task_data->object),
+ ast_sorcery_object_get_id(task_data->object));
+ if (!object) {
+ ast_debug(1, "Backend no longer has object type '%s' ID '%s'. Removing from cache\n",
+ ast_sorcery_object_get_type(task_data->object),
+ ast_sorcery_object_get_id(task_data->object));
+ sorcery_memory_cache_delete(task_data->sorcery, task_data->cache,
+ task_data->object);
+ } else {
+ ast_debug(1, "Refreshing stale cache object type '%s' ID '%s'\n",
+ ast_sorcery_object_get_type(task_data->object),
+ ast_sorcery_object_get_id(task_data->object));
+ sorcery_memory_cache_create(task_data->sorcery, task_data->cache,
+ object);
+ }
+
+ ao2_ref(task_data, -1);
+ end_stale_update();
+
+ return 0;
+}
+
/*!
* \internal
* \brief Callback function to retrieve an object from a memory cache
@@ -549,9 +658,37 @@
struct sorcery_memory_cached_object *cached;
void *object;
+ if (is_stale_update()) {
+ return NULL;
+ }
+
cached = ao2_find(cache->objects, id, OBJ_SEARCH_KEY);
if (!cached) {
return NULL;
+ }
+
+ if (cache->object_lifetime_stale) {
+ struct timeval elapsed;
+
+ elapsed = ast_tvsub(ast_tvnow(), cached->created);
+ if (elapsed.tv_sec > cache->object_lifetime_stale) {
+ ao2_lock(cached);
+ if (cached->stale_update_sched_id == -1) {
+ struct stale_update_task_data *task_data;
+
+ task_data = stale_update_task_data_alloc((struct ast_sorcery *)sorcery, cache,
+ type, cached->object);
+ if (task_data) {
+ ast_debug(1, "Cached sorcery object type '%s' ID '%s' is stale. Refreshing\n",
+ type, id);
+ cached->stale_update_sched_id = ast_sched_add(sched, 1, stale_item_update, task_data);
+ } else {
+ ast_log(LOG_ERROR, "Unable to update stale cached object type '%s', ID '%s'.\n",
+ type, id);
+ }
+ }
+ ao2_unlock(cached);
+ }
}
object = ao2_bump(cached->object);
@@ -1462,6 +1599,240 @@
return res;
}
+/*!
+ * \brief Backend data that the mock sorcery wizard uses to create objects
+ */
+static struct backend_data {
+ /*! An arbitrary data field */
+ int salt;
+ /*! Another arbitrary data field */
+ int pepper;
+ /*! Indicates whether the backend has data */
+ int exists;
+} *real_backend_data;
+
+/*!
+ * \brief Sorcery object created based on backend data
+ */
+struct test_data {
+ SORCERY_OBJECT(details);
+ /*! Mirrors the backend data's salt field */
+ int salt;
+ /*! Mirrors the backend data's pepper field */
+ int pepper;
+};
+
+/*!
+ * \brief Allocation callback for test_data sorcery object
+ */
+static void *test_data_alloc(const char *id) {
+ return ast_sorcery_generic_alloc(sizeof(struct test_data), NULL);
+}
+
+/*!
+ * \brief Callback for retrieving sorcery object by ID
+ *
+ * The mock wizard uses the \ref real_backend_data in order to construct
+ * objects. If the backend data is "nonexisent" then no object is returned.
+ * Otherwise, an object is created that has the backend data's salt and
+ * pepper values copied.
+ *
+ * \param sorcery The sorcery instance
+ * \param data Unused
+ * \param type The object type. Will always be "test".
+ * \param id The object id. Will always be "test".
+ *
+ * \retval NULL Backend data does not exist
+ * \retval non-NULL An object representing the backend data
+ */
+static void *mock_retrieve_id(const struct ast_sorcery *sorcery, void *data,
+ const char *type, const char *id)
+{
+ struct test_data *b_data;
+
+ if (!real_backend_data->exists) {
+ return NULL;
+ }
+
+ b_data = ast_sorcery_alloc(sorcery, type, id);
+ if (!b_data) {
+ return NULL;
+ }
+
+ b_data->salt = real_backend_data->salt;
+ b_data->pepper = real_backend_data->pepper;
+ return b_data;
+}
+
+/*!
+ * \brief A mock sorcery wizard used for the stale test
+ */
+static struct ast_sorcery_wizard mock_wizard = {
+ .name = "mock",
+ .retrieve_id = mock_retrieve_id,
+};
+
+/*!
+ * \brief Wait for the cache to be updated after a stale object is retrieved.
+ *
+ * Since the cache does not know what type of objects it is dealing with, and
+ * since we do not have the internals of the cache, the only way to make this
+ * determination is to continuously retrieve an object from the cache until
+ * we retrieve a different object than we had previously retrieved.
+ *
+ * \param sorcery The sorcery instance
+ * \param previous_object The object we had previously retrieved from the cache
+ * \param[out] new_object The new object we retrieve from the cache
+ *
+ * \retval 0 Successfully retrieved a new object from the cache
+ * \retval non-zero Failed to retrieve a new object from the cache
+ */
+static int wait_for_cache_update(const struct ast_sorcery *sorcery,
+ void *previous_object, struct test_data **new_object)
+{
+ struct timeval start = ast_tvnow();
+
+ while (ast_remaining_ms(start, 5000) > 0) {
+ void *object;
+
+ object = ast_sorcery_retrieve_by_id(sorcery, "test", "test");
+ if (object != previous_object) {
+ *new_object = object;
+ return 0;
+ }
+ ao2_cleanup(object);
+ }
+
+ return -1;
+}
+
+AST_TEST_DEFINE(stale)
+{
+ int res = AST_TEST_FAIL;
+ struct ast_sorcery *sorcery = NULL;
+ struct test_data *backend_object;
+ struct backend_data iterations[] = {
+ { .salt = 1, .pepper = 2, .exists = 1 },
+ { .salt = 568729, .pepper = -234123, .exists = 1 },
+ { .salt = 0, .pepper = 0, .exists = 0 },
+ };
+ struct backend_data initial = {
+ .salt = 0,
+ .pepper = 0,
+ .exists = 1,
+ };
+ int i;
+
+ switch (cmd) {
+ case TEST_INIT:
+ info->name = "stale";
+ info->category = "/res/res_sorcery_memory_cache/";
+ info->summary = "Ensure that stale objects are replaced with updated objects";
+ info->description = "This test performs the following:\n"
+ "\t* Create a sorcery instance with two wizards"
+ "\t\t* The first is a memory cache that marks items stale after 3 seconds\n"
+ "\t\t* The second is a mock of a back-end\n"
+ "\t* Pre-populates the cache by retrieving some initial data from the backend.\n"
+ "\t* Performs iterations of the following:\n"
+ "\t\t* Update backend data with new values\n"
+ "\t\t* Retrieve item from the cache\n"
+ "\t\t* Ensure the retrieved item does not have the new backend values\n"
+ "\t\t* Wait for cached object to become stale\n"
+ "\t\t* Retrieve the stale cached object\n"
+ "\t\t* Ensure that the stale object retrieved is the same as the fresh one from earlier\n"
+ "\t\t* Wait for the cache to update with new data\n"
+ "\t\t* Ensure that new data in the cache matches backend data\n";
+ return AST_TEST_NOT_RUN;
+ case TEST_EXECUTE:
+ break;
+ }
+
+ ast_sorcery_wizard_register(&mock_wizard);
+
+ sorcery = ast_sorcery_open();
+ if (!sorcery) {
+ ast_test_status_update(test, "Failed to create sorcery instance\n");
+ goto cleanup;
+ }
+
+ ast_sorcery_apply_wizard_mapping(sorcery, "test", "memory_cache",
+ "object_lifetime_stale=3", 1);
+ ast_sorcery_apply_wizard_mapping(sorcery, "test", "mock", NULL, 0);
+ ast_sorcery_internal_object_register(sorcery, "test", test_data_alloc, NULL, NULL);
+
+ /* Prepopulate the cache */
+ real_backend_data = &initial;
+
+ backend_object = ast_sorcery_retrieve_by_id(sorcery, "test", "test");
+ if (!backend_object) {
+ ast_test_status_update(test, "Unable to retrieve backend data and populate the cache\n");
+ goto cleanup;
+ }
+ ao2_ref(backend_object, -1);
+
+ for (i = 0; i < ARRAY_LEN(iterations); ++i) {
+ RAII_VAR(struct test_data *, cache_fresh, NULL, ao2_cleanup);
+ RAII_VAR(struct test_data *, cache_stale, NULL, ao2_cleanup);
+ RAII_VAR(struct test_data *, cache_new, NULL, ao2_cleanup);
+
+ real_backend_data = &iterations[i];
+
+ ast_test_status_update(test, "Begininning iteration %d\n", i);
+
+ cache_fresh = ast_sorcery_retrieve_by_id(sorcery, "test", "test");
+ if (!cache_fresh) {
+ ast_test_status_update(test, "Unable to retrieve fresh cached object\n");
+ goto cleanup;
+ }
+
+ if (cache_fresh->salt == iterations[i].salt || cache_fresh->pepper == iterations[i].pepper) {
+ ast_test_status_update(test, "Fresh cached object has unexpected values. Did we hit the backend?\n");
+ goto cleanup;
+ }
+
+ sleep(5);
+
+ cache_stale = ast_sorcery_retrieve_by_id(sorcery, "test", "test");
+ if (!cache_stale) {
+ ast_test_status_update(test, "Unable to retrieve stale cached object\n");
+ goto cleanup;
+ }
+
+ if (cache_stale != cache_fresh) {
+ ast_test_status_update(test, "Stale cache hit retrieved different object than fresh cache hit\n");
+ goto cleanup;
+ }
+
+ if (wait_for_cache_update(sorcery, cache_stale, &cache_new)) {
+ ast_test_status_update(test, "Cache was not updated\n");
+ goto cleanup;
+ }
+
+ if (iterations[i].exists) {
+ if (!cache_new) {
+ ast_test_status_update(test, "Failed to retrieve item from cache when there should be one present\n");
+ goto cleanup;
+ } else if (cache_new->salt != iterations[i].salt ||
+ cache_new->pepper != iterations[i].pepper) {
+ ast_test_status_update(test, "New cached item has unexpected values\n");
+ goto cleanup;
+ }
+ } else if (cache_new) {
+ ast_test_status_update(test, "Retrieved a cached item when there should not have been one present\n");
+ goto cleanup;
+ }
+ }
+
+ res = AST_TEST_PASS;
+
+cleanup:
+ if (sorcery) {
+ ast_sorcery_unref(sorcery);
+ }
+ ast_sorcery_wizard_unregister(&mock_wizard);
+ return res;
+}
+
#endif
static int unload_module(void)
@@ -1482,6 +1853,7 @@
AST_TEST_UNREGISTER(delete);
AST_TEST_UNREGISTER(maximum_objects);
AST_TEST_UNREGISTER(expiration);
+ AST_TEST_UNREGISTER(stale);
return 0;
}
@@ -1521,6 +1893,7 @@
AST_TEST_REGISTER(delete);
AST_TEST_REGISTER(maximum_objects);
AST_TEST_REGISTER(expiration);
+ AST_TEST_REGISTER(stale);
return AST_MODULE_LOAD_SUCCESS;
}
--
To view, visit https://gerrit.asterisk.org/829
To unsubscribe, visit https://gerrit.asterisk.org/settings
Gerrit-MessageType: newchange
Gerrit-Change-Id: I9bd7c049adf6939bfe2899f393c2bfbbf412d217
Gerrit-PatchSet: 1
Gerrit-Project: asterisk
Gerrit-Branch: certified/13.1
Gerrit-Owner: Mark Michelson <mmichelson at digium.com>
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