Merge pull request #7 from spark/feature/rate-limit-publish

Rate limit Spark.publish to 4 events per second

Author: Zachary Crockett

src/spark_protocol.cpp

@@ -445,10 +445,22 @@ int SparkProtocol::variable_value(unsigned char *buf,
   return buflen;
 }
 
-// Returns true on success, false on sending timeout failure
+// Returns true on success, false on sending timeout or rate-limiting failure
 bool SparkProtocol::send_event(const char *event_name, const char *data,
                                int ttl, EventType::Enum event_type)
 {
+  static system_tick_t recent_event_ticks[5] = { -1000, -1000, -1000, -1000, -1000 };
+  static int evt_tick_idx = 0;
+
+  system_tick_t now = recent_event_ticks[evt_tick_idx] = callback_millis();
+  evt_tick_idx++;
+  evt_tick_idx %= 5;
+  if (now - recent_event_ticks[evt_tick_idx] < 1000)
+  {
+    // exceeded allowable burst of 4 events per second
+    return false;
+  }
+
   uint16_t msg_id = next_message_id();
   size_t msglen = event(queue + 2, msg_id, event_name, data, ttl, event_type);
 

tests/ConstructorFixture.cpp

@@ -295,9 +295,11 @@ void ConstructorFixture::mock_signal(bool on)
   signal_called_with = on;
 }
 
+system_tick_t ConstructorFixture::next_millis = 0;
+
 system_tick_t ConstructorFixture::mock_millis(void)
 {
-  return 0;
+  return next_millis;
 }
 
 bool ConstructorFixture::mock_ota_status_check(void)

tests/ConstructorFixture.h

@@ -53,6 +53,7 @@ struct ConstructorFixture
   static void mock_signal(bool on);
   static bool signal_called_with;
   static int variable_to_get;
+  static system_tick_t next_millis;
   static system_tick_t mock_millis(void);
   static bool mock_ota_status_check(void);
   static SparkReturnType::Enum mock_variable_type(const char *variable_key);

tests/TestSparkProtocol.cpp

@@ -317,4 +317,48 @@ SUITE(SparkProtocolConstruction)
     spark_protocol.send_event("lake-depth/1", "28m", 21600, EventType::PRIVATE);
     CHECK_ARRAY_EQUAL(expected, sent_buf_0, 34);
   }
+
+  TEST_FIXTURE(ConstructorFixture, PublishingBurst4EventsSucceeds)
+  {
+    bool success[4];
+    next_millis = 1000;
+    success[0] = spark_protocol.send_event("a", NULL, 60, EventType::PUBLIC);
+    success[1] = spark_protocol.send_event("b", NULL, 60, EventType::PUBLIC);
+    success[2] = spark_protocol.send_event("c", NULL, 60, EventType::PUBLIC);
+    success[3] = spark_protocol.send_event("d", NULL, 60, EventType::PUBLIC);
+    CHECK(success[0] && success[1] && success[2] && success[3]);
+  }
+
+  TEST_FIXTURE(ConstructorFixture, PublishingBurst5EventsFails)
+  {
+    bool success[5];
+    next_millis = 2000;
+    success[0] = spark_protocol.send_event("a", NULL, 60, EventType::PUBLIC);
+    success[1] = spark_protocol.send_event("b", NULL, 60, EventType::PUBLIC);
+    success[2] = spark_protocol.send_event("c", NULL, 60, EventType::PUBLIC);
+    success[3] = spark_protocol.send_event("d", NULL, 60, EventType::PUBLIC);
+    success[4] = spark_protocol.send_event("e", NULL, 60, EventType::PUBLIC);
+    CHECK(success[0] && success[1] && success[2] && success[3] && !success[4]);
+  }
+
+  TEST_FIXTURE(ConstructorFixture, PublishingBurst4Wait1SBurst4AgainSucceeds)
+  {
+    bool success[4];
+
+    next_millis = 3000;
+    success[0] = spark_protocol.send_event("a", NULL, 60, EventType::PUBLIC);
+    success[1] = spark_protocol.send_event("b", NULL, 60, EventType::PUBLIC);
+    success[2] = spark_protocol.send_event("c", NULL, 60, EventType::PUBLIC);
+    success[3] = spark_protocol.send_event("d", NULL, 60, EventType::PUBLIC);
+    bool first_burst_success = success[0] && success[1] && success[2] && success[3];
+
+    next_millis = 4000;
+    success[0] = spark_protocol.send_event("a", NULL, 60, EventType::PUBLIC);
+    success[1] = spark_protocol.send_event("b", NULL, 60, EventType::PUBLIC);
+    success[2] = spark_protocol.send_event("c", NULL, 60, EventType::PUBLIC);
+    success[3] = spark_protocol.send_event("d", NULL, 60, EventType::PUBLIC);
+    bool second_burst_success = success[0] && success[1] && success[2] && success[3];
+
+    CHECK(first_burst_success && second_burst_success);
+  }
 }