Fix: evaluate condition/trigger on subscription
authorJonathan Rajotte <jonathan.rajotte-julien@efficios.com>
Tue, 4 Jul 2017 18:58:43 +0000 (14:58 -0400)
committerJérémie Galarneau <jeremie.galarneau@efficios.com>
Wed, 26 Jul 2017 22:20:47 +0000 (18:20 -0400)
Signed-off-by: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
src/bin/lttng-sessiond/notification-thread-events.c

index 751e665bdc624936a8401fd307ae75ff93656978..5e53b79a1661a458e5d4bada395350b152f6d725 100644 (file)
@@ -154,6 +154,20 @@ struct channel_state_sample {
        uint64_t lowest_usage;
 };
 
+static unsigned long hash_channel_key(struct channel_key *key);
+static int evaluate_condition(struct lttng_condition *condition,
+               struct lttng_evaluation **evaluation,
+               struct notification_thread_state *state,
+               struct channel_state_sample *previous_sample,
+               struct channel_state_sample *latest_sample,
+               uint64_t buffer_capacity);
+static
+int send_evaluation_to_clients(struct lttng_trigger *trigger,
+               struct lttng_evaluation *evaluation,
+               struct notification_client_list *client_list,
+               struct notification_thread_state *state,
+               uid_t channel_uid, gid_t channel_gid);
+
 static
 int match_client(struct cds_lfht_node *node, const void *key)
 {
@@ -308,6 +322,16 @@ unsigned long lttng_condition_hash(struct lttng_condition *condition)
        }
 }
 
+static
+unsigned long hash_channel_key(struct channel_key *key)
+{
+       unsigned long key_hash = hash_key_u64(&key->key, lttng_ht_seed);
+       unsigned long domain_hash = hash_key_ulong(
+               (void *) (unsigned long) key->domain, lttng_ht_seed);
+
+       return key_hash ^ domain_hash;
+}
+
 static
 void channel_info_destroy(struct channel_info *channel_info)
 {
@@ -357,6 +381,126 @@ error:
        return NULL;
 }
 
+/* This function must be called with the RCU read lock held. */
+static
+int evaluate_condition_for_client(struct lttng_trigger *trigger,
+               struct lttng_condition *condition,
+               struct notification_client *client,
+               struct notification_thread_state *state)
+{
+       int ret;
+       struct cds_lfht_iter iter;
+       struct cds_lfht_node *node;
+       struct channel_info *channel_info = NULL;
+       struct channel_key *channel_key = NULL;
+       struct channel_state_sample *last_sample = NULL;
+       struct lttng_channel_trigger_list *channel_trigger_list = NULL;
+       struct lttng_evaluation *evaluation = NULL;
+       struct notification_client_list client_list = { 0 };
+       struct notification_client_list_element client_list_element = { 0 };
+
+       assert(trigger);
+       assert(condition);
+       assert(client);
+       assert(state);
+
+       /* Find the channel associated with the trigger. */
+       cds_lfht_for_each_entry(state->channel_triggers_ht, &iter,
+                       channel_trigger_list , channel_triggers_ht_node) {
+               struct lttng_trigger_list_element *element;
+
+               cds_list_for_each_entry(element, &channel_trigger_list->list, node) {
+                       struct lttng_condition *current_condition =
+                               lttng_trigger_get_condition(
+                                               element->trigger);
+
+                       assert(current_condition);
+                       if (!lttng_condition_is_equal(condition,
+                                               current_condition)) {
+                               continue;
+                       }
+
+                       /* Found the trigger, save the channel key. */
+                       channel_key = &channel_trigger_list->channel_key;
+                       break;
+               }
+               if (channel_key) {
+                       /* The channel key was found stop iteration. */
+                       break;
+               }
+       }
+
+       if (!channel_key){
+               /* No channel found; normal exit. */
+               DBG("[notification-thread] No channel associated with newly subscribed-to condition");
+               ret = 0;
+               goto end;
+       }
+
+       /* Fetch channel info for the matching channel. */
+       cds_lfht_lookup(state->channels_ht,
+                       hash_channel_key(channel_key),
+                       match_channel_info,
+                       channel_key,
+                       &iter);
+       node = cds_lfht_iter_get_node(&iter);
+       assert(node);
+       channel_info = caa_container_of(node, struct channel_info,
+                       channels_ht_node);
+
+       /* Retrieve the channel's last sample, if it exists. */
+       cds_lfht_lookup(state->channel_state_ht,
+                       hash_channel_key(channel_key),
+                       match_channel_state_sample,
+                       channel_key,
+                       &iter);
+       node = cds_lfht_iter_get_node(&iter);
+       if (node) {
+               last_sample = caa_container_of(node,
+                               struct channel_state_sample,
+                               channel_state_ht_node);
+       } else {
+               /* Nothing to evaluate, no sample was ever taken. Normal exit */
+               DBG("[notification-thread] No channel sample associated with newly subscribed-to condition");
+               ret = 0;
+               goto end;
+       }
+
+       ret = evaluate_condition(condition, &evaluation, state, NULL,
+                       last_sample, channel_info->capacity);
+       if (ret) {
+               WARN("[notification-thread] Fatal error occured while evaluating a newly subscribed-to condition");
+               goto end;
+       }
+
+       if (!evaluation) {
+               /* Evaluation yielded nothing. Normal exit. */
+               DBG("[notification-thread] Newly subscribed-to condition evaluated to false, nothing to report to client");
+               ret = 0;
+               goto end;
+       }
+
+       /*
+        * Create a temporary client list with the client currently
+        * subscribing.
+        */
+       cds_lfht_node_init(&client_list.notification_trigger_ht_node);
+       CDS_INIT_LIST_HEAD(&client_list.list);
+       client_list.trigger = trigger;
+
+       CDS_INIT_LIST_HEAD(&client_list_element.node);
+       client_list_element.client = client;
+       cds_list_add(&client_list_element.node, &client_list.list);
+
+       /* Send evaluation result to the newly-subscribed client. */
+       DBG("[notification-thread] Newly subscribed-to condition evaluated to true, notifying client");
+       ret = send_evaluation_to_clients(trigger, evaluation, &client_list,
+                       state, channel_info->uid, channel_info->gid);
+
+end:
+       return ret;
+}
+
 static
 int notification_thread_client_subscribe(struct notification_client *client,
                struct lttng_condition *condition,
@@ -404,11 +548,6 @@ int notification_thread_client_subscribe(struct notification_client *client,
        condition_list_element->condition = condition;
        cds_list_add(&condition_list_element->node, &client->condition_list);
 
-       /*
-        * Add the client to the list of clients interested in a given trigger
-        * if a "notification" trigger with a corresponding condition was
-        * added prior.
-        */
        cds_lfht_lookup(state->notification_trigger_clients_ht,
                        lttng_condition_hash(condition),
                        match_client_list_condition,
@@ -422,6 +561,18 @@ int notification_thread_client_subscribe(struct notification_client *client,
 
        client_list = caa_container_of(node, struct notification_client_list,
                        notification_trigger_ht_node);
+       if (evaluate_condition_for_client(client_list->trigger, condition,
+                       client, state)) {
+               WARN("[notification-thread] Evaluation of a condition on client subscription failed, aborting.");
+               ret = -1;
+               goto end_unlock;
+       }
+
+       /*
+        * Add the client to the list of clients interested in a given trigger
+        * if a "notification" trigger with a corresponding condition was
+        * added prior.
+        */
        client_list_element->client = client;
        CDS_INIT_LIST_HEAD(&client_list_element->node);
        cds_list_add(&client_list_element->node, &client_list->list);
@@ -642,13 +793,6 @@ bool trigger_applies_to_client(struct lttng_trigger *trigger,
        return applies;
 }
 
-static
-unsigned long hash_channel_key(struct channel_key *key)
-{
-       return hash_key_u64(&key->key, lttng_ht_seed) ^ hash_key_ulong(
-               (void *) (unsigned long) key->domain, lttng_ht_seed);
-}
-
 static
 int handle_notification_thread_command_add_channel(
        struct notification_thread_state *state,
@@ -986,7 +1130,6 @@ int handle_notification_thread_command_register_trigger(
                                &iter);
                node = cds_lfht_iter_get_node(&iter);
                assert(node);
-               /* Free the list of triggers associated with this channel. */
                trigger_list = caa_container_of(node,
                                struct lttng_channel_trigger_list,
                                channel_triggers_ht_node);
@@ -999,6 +1142,7 @@ int handle_notification_thread_command_register_trigger(
                CDS_INIT_LIST_HEAD(&trigger_list_element->node);
                trigger_list_element->trigger = trigger;
                cds_list_add(&trigger_list_element->node, &trigger_list->list);
+
                /* A trigger can only apply to one channel. */
                break;
        }
@@ -1077,6 +1221,8 @@ int handle_notification_thread_command_unregister_trigger(
 
                        DBG("[notification-thread] Removed trigger from channel_triggers_ht");
                        cds_list_del(&trigger_element->node);
+                       /* A trigger can only appear once per channel */
+                       break;
                }
        }
 
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