recovery_node.cpp

// Copyright (c) 2019 Intel Corporation
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
 
#include <string>
#include "nav2_behavior_tree/plugins/control/recovery_node.hpp"
 
namespace nav2_behavior_tree
{
 
RecoveryNode::RecoveryNode(
  const std::string & name,
  const BT::NodeConfiguration & conf)
: BT::ControlNode::ControlNode(name, conf),
  current_child_idx_(0),
  number_of_retries_(1),
  retry_count_(0)
{
}
 
BT::NodeStatus RecoveryNode::tick()
{
  getInput("number_of_retries", number_of_retries_);
  const unsigned children_count = children_nodes_.size();
 
  if (children_count != 2) {
    throw BT::BehaviorTreeException("Recovery Node '" + name() + "' must only have 2 children.");
  }
 
  setStatus(BT::NodeStatus::RUNNING);
 
  while (current_child_idx_ < children_count && retry_count_ <= number_of_retries_) {
    TreeNode * child_node = children_nodes_[current_child_idx_];
    const BT::NodeStatus child_status = child_node->executeTick();
 
    if (current_child_idx_ == 0) {
      switch (child_status) {
        case BT::NodeStatus::SKIPPED:
          // If first child is skipped, the entire branch is considered skipped
          halt();
          return BT::NodeStatus::SKIPPED;
 
        case BT::NodeStatus::SUCCESS:
          // reset node and return success when first child returns success
          // also halt the recovery action as the main action is successful, reset its state
          ControlNode::haltChild(1);
          halt();
          return BT::NodeStatus::SUCCESS;
 
        case BT::NodeStatus::RUNNING:
          return BT::NodeStatus::RUNNING;
 
        case BT::NodeStatus::FAILURE:
          {
            if (retry_count_ < number_of_retries_) {
              // halt first child and tick second child in next iteration
              ControlNode::haltChild(0);
              current_child_idx_++;
              break;
            } else {
              // reset node and return failure when max retries has been exceeded
              halt();
              return BT::NodeStatus::FAILURE;
            }
          }
 
        default:
          throw BT::LogicError("A child node must never return IDLE");
      }  // end switch
 
    } else if (current_child_idx_ == 1) {
      switch (child_status) {
        case BT::NodeStatus::SKIPPED:
          {
            // if we skip the recovery (maybe a precondition fails), then we
            // should assume that no recovery is possible. For this reason,
            // we should return FAILURE and reset the index.
            // This does not count as a retry.
            current_child_idx_ = 0;
            ControlNode::haltChild(1);
            return BT::NodeStatus::FAILURE;
          }
        case BT::NodeStatus::RUNNING:
          return child_status;
 
        case BT::NodeStatus::SUCCESS:
          {
            // halt second child, increment recovery count, and tick first child in next iteration
            ControlNode::haltChild(1);
            retry_count_++;
            current_child_idx_ = 0;
          }
          break;
 
        case BT::NodeStatus::FAILURE:
          // reset node and return failure if second child fails
          halt();
          return BT::NodeStatus::FAILURE;
 
        default:
          throw BT::LogicError("A child node must never return IDLE");
      }  // end switch
    }
  }  // end while loop
 
  // reset node and return failure
  halt();
  return BT::NodeStatus::FAILURE;
}
 
void RecoveryNode::halt()
{
  ControlNode::halt();
  retry_count_ = 0;
  current_child_idx_ = 0;
}
 
}  // namespace nav2_behavior_tree
 
#include "behaviortree_cpp/bt_factory.h"
BT_REGISTER_NODES(factory)
{
  factory.registerNodeType<nav2_behavior_tree::RecoveryNode>("RecoveryNode");
}