Modifies timers API to select autostart state

rclcpp/include/rclcpp/create_timer.hpp

@@ -39,13 +39,15 @@ create_timer(
   rclcpp::Clock::SharedPtr clock,
   rclcpp::Duration period,
   CallbackT && callback,
-  rclcpp::CallbackGroup::SharedPtr group = nullptr)
+  rclcpp::CallbackGroup::SharedPtr group = nullptr,
+  bool autostart = true)
 {
   auto timer = rclcpp::GenericTimer<CallbackT>::make_shared(
     clock,
     period.to_chrono<std::chrono::nanoseconds>(),
     std::forward<CallbackT>(callback),
-    node_base->get_context());
+    node_base->get_context(),
+    autostart);
 
   node_timers->add_timer(timer, group);
   return timer;
@@ -59,15 +61,17 @@ create_timer(
   rclcpp::Clock::SharedPtr clock,
   rclcpp::Duration period,
   CallbackT && callback,
-  rclcpp::CallbackGroup::SharedPtr group = nullptr)
+  rclcpp::CallbackGroup::SharedPtr group = nullptr,
+  bool autostart = true)
 {
   return create_timer(
     rclcpp::node_interfaces::get_node_base_interface(node),
     rclcpp::node_interfaces::get_node_timers_interface(node),
     clock,
     period,
     std::forward<CallbackT>(callback),
-    group);
+    group,
+    autostart);
 }
 
 /// Convenience method to create a timer with node resources.
@@ -92,7 +96,8 @@ create_wall_timer(
   CallbackT callback,
   rclcpp::CallbackGroup::SharedPtr group,
   node_interfaces::NodeBaseInterface * node_base,
-  node_interfaces::NodeTimersInterface * node_timers)
+  node_interfaces::NodeTimersInterface * node_timers,
+  bool autostart = true)
 {
   if (node_base == nullptr) {
     throw std::invalid_argument{"input node_base cannot be null"};
@@ -133,7 +138,7 @@ create_wall_timer(
   }
 
   auto timer = rclcpp::WallTimer<CallbackT>::make_shared(
-    period_ns, std::move(callback), node_base->get_context());
+    period_ns, std::move(callback), node_base->get_context(), autostart);
   node_timers->add_timer(timer, group);
   return timer;
 }

rclcpp/include/rclcpp/node.hpp

@@ -232,13 +232,15 @@ class Node : public std::enable_shared_from_this<Node>
    * \param[in] period Time interval between triggers of the callback.
    * \param[in] callback User-defined callback function.
    * \param[in] group Callback group to execute this timer's callback in.
+   * \param[in] autostart The state of the clock on initialization.
    */
   template<typename DurationRepT = int64_t, typename DurationT = std::milli, typename CallbackT>
   typename rclcpp::WallTimer<CallbackT>::SharedPtr
   create_wall_timer(
     std::chrono::duration<DurationRepT, DurationT> period,
     CallbackT callback,
-    rclcpp::CallbackGroup::SharedPtr group = nullptr);
+    rclcpp::CallbackGroup::SharedPtr group = nullptr,
+    bool autostart = true);
 
   /// Create and return a Client.
   /**

rclcpp/include/rclcpp/node_impl.hpp

@@ -110,14 +110,16 @@ typename rclcpp::WallTimer<CallbackT>::SharedPtr
 Node::create_wall_timer(
   std::chrono::duration<DurationRepT, DurationT> period,
   CallbackT callback,
-  rclcpp::CallbackGroup::SharedPtr group)
+  rclcpp::CallbackGroup::SharedPtr group,
+  bool autostart)
 {
   return rclcpp::create_wall_timer(
     period,
     std::move(callback),
     group,
     this->node_base_.get(),
-    this->node_timers_.get());
+    this->node_timers_.get(),
+    autostart);
 }
 
 template<typename ServiceT>

rclcpp/include/rclcpp/timer.hpp

@@ -53,12 +53,14 @@ class TimerBase
    * \param clock A clock to use for time and sleeping
    * \param period The interval at which the timer fires
    * \param context node context
+   * \param autostart timer state on initialization
    */
   RCLCPP_PUBLIC
   explicit TimerBase(
     Clock::SharedPtr clock,
     std::chrono::nanoseconds period,
-    rclcpp::Context::SharedPtr context);
+    rclcpp::Context::SharedPtr context,
+    bool autostart = true);
 
   /// TimerBase destructor
   RCLCPP_PUBLIC
@@ -179,12 +181,13 @@ class GenericTimer : public TimerBase
    * \param[in] period The interval at which the timer fires.
    * \param[in] callback User-specified callback function.
    * \param[in] context custom context to be used.
+   * \param autostart timer state on initialization
    */
   explicit GenericTimer(
     Clock::SharedPtr clock, std::chrono::nanoseconds period, FunctorT && callback,
-    rclcpp::Context::SharedPtr context
+    rclcpp::Context::SharedPtr context, bool autostart = true
   )
-  : TimerBase(clock, period, context), callback_(std::forward<FunctorT>(callback))
+  : TimerBase(clock, period, context, autostart), callback_(std::forward<FunctorT>(callback))
   {
     TRACEPOINT(
       rclcpp_timer_callback_added,
@@ -287,13 +290,15 @@ class WallTimer : public GenericTimer<FunctorT>
    * \param period The interval at which the timer fires
    * \param callback The callback function to execute every interval
    * \param context node context
+   * \param autostart timer state on initialization
    */
   WallTimer(
     std::chrono::nanoseconds period,
     FunctorT && callback,
-    rclcpp::Context::SharedPtr context)
+    rclcpp::Context::SharedPtr context,
+    bool autostart = true)
   : GenericTimer<FunctorT>(
-      std::make_shared<Clock>(RCL_STEADY_TIME), period, std::move(callback), context)
+      std::make_shared<Clock>(RCL_STEADY_TIME), period, std::move(callback), context, autostart)
   {}
 
 protected:

rclcpp/src/rclcpp/timer.cpp

@@ -29,7 +29,8 @@ using rclcpp::TimerBase;
 TimerBase::TimerBase(
   rclcpp::Clock::SharedPtr clock,
   std::chrono::nanoseconds period,
-  rclcpp::Context::SharedPtr context)
+  rclcpp::Context::SharedPtr context,
+  bool autostart)
 : clock_(clock), timer_handle_(nullptr)
 {
   if (nullptr == context) {
@@ -62,8 +63,8 @@ TimerBase::TimerBase(
   {
     std::lock_guard<std::mutex> clock_guard(clock_->get_clock_mutex());
     rcl_ret_t ret = rcl_timer_init(
-      timer_handle_.get(), clock_handle, rcl_context.get(), period.count(), nullptr,
-      rcl_get_default_allocator());
+      timer_handle_.get(), clock_handle, rcl_context.get(), period.count(),
+      nullptr, rcl_get_default_allocator(), autostart);
     if (ret != RCL_RET_OK) {
       rclcpp::exceptions::throw_from_rcl_error(ret, "Couldn't initialize rcl timer handle");
     }

rclcpp/test/rclcpp/test_create_timer.cpp

@@ -133,3 +133,28 @@ TEST(TestCreateTimer, timer_function_pointer)
 
   rclcpp::shutdown();
 }
+
+TEST(TestCreateTimer, timer_without_autostart)
+{
+  rclcpp::init(0, nullptr);
+  auto node = std::make_shared<rclcpp::Node>("test_create_timer_node");
+
+  rclcpp::TimerBase::SharedPtr timer;
+  timer = rclcpp::create_timer(
+    node,
+    node->get_clock(),
+    rclcpp::Duration(0ms),
+    []() {},
+    nullptr,
+    false);
+
+  ASSERT_TRUE(timer->is_canceled());
+
+  timer->reset();
+
+  ASSERT_FALSE(timer->is_canceled());
+
+  timer->cancel();
+
+  rclcpp::shutdown();
+}

rclcpp/test/rclcpp/test_timer.cpp

@@ -59,6 +59,20 @@ class TestTimer : public ::testing::Test
     );
     EXPECT_TRUE(timer->is_steady());
 
+    timer_without_autostart = test_node->create_wall_timer(
+      100ms,
+      [this]() -> void
+      {
+        this->has_timer_run.store(true);
+
+        if (this->cancel_timer.load()) {
+          this->timer->cancel();
+        }
+        // prevent any tests running timer from blocking
+        this->executor->cancel();
+      }, nullptr, false);
+    EXPECT_TRUE(timer_without_autostart->is_steady());
+
     executor->add_node(test_node);
     // don't start spinning, let the test dictate when
   }
@@ -78,6 +92,7 @@ class TestTimer : public ::testing::Test
   std::atomic<bool> cancel_timer;
   rclcpp::Node::SharedPtr test_node;
   std::shared_ptr<rclcpp::TimerBase> timer;
+  std::shared_ptr<rclcpp::TimerBase> timer_without_autostart;
   std::shared_ptr<rclcpp::executors::SingleThreadedExecutor> executor;
 };
 
@@ -283,3 +298,12 @@ TEST_F(TestTimer, test_failures_with_exceptions)
       std::runtime_error("Timer could not get time until next call: error not set"));
   }
 }
+
+/// Simple test of a timer without autostart
+TEST_F(TestTimer, test_timer_without_autostart)
+{
+  EXPECT_TRUE(timer_without_autostart->is_canceled());
+  // Reset to change start timer
+  timer_without_autostart->reset();
+  EXPECT_FALSE(timer_without_autostart->is_canceled());
+}