Add new queries per second (QPS) metric exposed via GET /api/stats/su…

…mmary as .queries.frequency and /api/info/ftl as .query_frequency. The QPS value is averaged over 30 seconds

Signed-off-by: DL6ER <[email protected]>

src/FTL.h

@@ -143,6 +143,10 @@
 // Default: 2592000 (once per month)
 #define DATABASE_MACVENDOR_INTERVAL 2592000
 
+// Over how many seonds should the query-per-second (QPS) value be averaged?
+// Default: 30 (seconds)
+#define QPS_AVGLEN 30
+
 // Use out own syscalls handling functions that will detect possible errors
 // and report accordingly in the log. This will make debugging FTL crash
 // caused by insufficient memory or by code bugs (not properly dealing

src/api/docs/content/specs/info.yaml

@@ -721,6 +721,10 @@ components:
               type: integer
               description: Currently used privacy level
               example: 0
+            query_frequency:
+              type: number
+              description: Average number of queries per second
+              example: 1.1
             clients:
               type: object
               properties:

src/api/docs/content/specs/stats.yaml

@@ -338,6 +338,10 @@ components:
               type: integer
               description: Number of queries replied to from cache or local configuration
               example: 9765
+            frequency:
+              type: number
+              description: Average number of queries per second
+              example: 1.1
             types:
               type: object
               description: Number of individual queries

src/api/info.c

@@ -548,6 +548,7 @@ static int get_ftl_obj(struct ftl_conn *api, cJSON *ftl)
 	const int db_denied = counters->database.domains.denied;
 	const int clients_total = counters->clients;
 	const int privacylevel = config.misc.privacylevel.v.privacy_level;
+	const double qps = get_qps();
 
 	// unique_clients: count only clients that have been active within the most recent 24 hours
 	int activeclients = 0;
@@ -575,6 +576,7 @@ static int get_ftl_obj(struct ftl_conn *api, cJSON *ftl)
 	JSON_ADD_ITEM_TO_OBJECT(ftl, "database", database);
 
 	JSON_ADD_NUMBER_TO_OBJECT(ftl, "privacy_level", privacylevel);
+	JSON_ADD_NUMBER_TO_OBJECT(ftl, "query_frequency", qps);
 
 	cJSON *clients = JSON_NEW_OBJECT();
 	JSON_ADD_NUMBER_TO_OBJECT(clients, "total",clients_total);

src/api/stats.c

@@ -143,6 +143,8 @@ int api_stats_summary(struct ftl_conn *api)
 	JSON_ADD_NUMBER_TO_OBJECT(queries, "forwarded", forwarded);
 	JSON_ADD_NUMBER_TO_OBJECT(queries, "cached", cached);
 
+	JSON_ADD_NUMBER_TO_OBJECT(queries, "frequency", get_qps());
+
 	cJSON *types = JSON_NEW_OBJECT();
 	int ret = get_query_types_obj(api, types);
 	if(ret != 0)

src/dnsmasq_interface.c

@@ -664,6 +664,9 @@ bool _FTL_new_query(const unsigned int flags, const char *name,
 		return false;
 	}
 
+	// Update rolling window of queries per second
+	update_qps(querytimestamp);
+
 	// Interface name is only available for regular queries, not for
 	// automatically generated DNSSEC queries
 	const char *interface = internal_query ? "-" : next_iface.name;

src/shmem.c

@@ -1206,3 +1206,46 @@ int __attribute__((pure)) is_shm_fd(const int fd)
 	// Not found
 	return 0;
 }
+
+// Update queries per second (qps) value
+// This is done in shared memory to allow for both UDP and TCP workers to
+// contribute.
+void update_qps(const double timestamp)
+{
+	// Get the timeslot for the current timestamp
+	const unsigned int slot = (unsigned int)timestamp % QPS_AVGLEN;
+
+	// Check if the timestamp is in the same slot as the last one
+	if(shmSettings->qps.last != slot)
+	{
+		// Reset all the slots in between
+		// This is relevant if less than one query per second is
+		// received and the intermediate slots are not updated
+		for(unsigned int i = (shmSettings->qps.last + 1) % QPS_AVGLEN; i != slot; i = (i + 1) % QPS_AVGLEN)
+			shmSettings->qps.buf[i] = 0;
+
+		// Reset the current slot
+		shmSettings->qps.buf[slot] = 0;
+
+		// Update the last slot index
+		shmSettings->qps.last = slot;
+	}
+
+	// Add the query
+	shmSettings->qps.buf[slot]++;
+}
+
+// Compute queries per second (qps) value
+double __attribute__((pure)) get_qps(void)
+{
+	// Compute the arithmetic mean of all slots
+	//        1  N
+	// QPS = --- Σ buf[i]
+	//        N  i=0
+	//
+	double qps = 0.0;
+	for(unsigned int i = 0; i < QPS_AVGLEN; i++)
+		qps += shmSettings->qps.buf[i];
+
+	return qps / QPS_AVGLEN;
+}

src/shmem.h

@@ -31,6 +31,10 @@ typedef struct {
 	pid_t pid;
 	unsigned int global_shm_counter;
 	unsigned int next_str_pos;
+	struct {
+		unsigned int last;
+		unsigned int buf[QPS_AVGLEN];
+	} qps;
 } ShmSettings;
 
 typedef struct {
@@ -145,4 +149,7 @@ void set_per_client_regex(const int clientID, const int regexID, const bool valu
 // Used in dnsmasq/utils.c
 int is_shm_fd(const int fd);
 
+void update_qps(const double timestamp);
+double get_qps(void) __attribute__((pure));
+
 #endif //SHARED_MEMORY_SERVER_H