File _service:obs_scm:README.en.md of Package actionlib

# actionlib

#### Description
In any large ROS based system, there are cases when someone would like to send a request to a node to perform some task, and also receive a reply to the request. This can currently be achieved via ROS services.

In some cases, however, if the service takes a long time to execute, the user might want the ability to cancel the request during execution or get periodic feedback about how the request is progressing. The actionlib package provides tools to create servers that execute long-running goals that can be preempted. It also provides a client interface in order to send requests to the server.

The ActionClient and ActionServer communicate via a "ROS Action Protocol", which is built on top of ROS messages. The client and server then provide a simple API for users to request goals (on the client side) or to execute goals (on the server side) via function calls and callbacks.

![Image text](https://gitee.com/gongjie7788/actionlib/raw/master/image/client_server_interaction.png)

#### Software Architecture
Software architecture description

In order for the client and server to communicate, we need to define a few messages on which they communicate. This is with an action specification. This defines the Goal, Feedback, and Result messages with which clients and servers communicate:

`Goal`<br>
To accomplish tasks using actions, we introduce the notion of a goal that can be sent to an ActionServer by an ActionClient. In the case of moving the base, the goal would be a PoseStamped message that contains information about where the robot should move to in the world. For controlling the tilting laser scanner, the goal would contain the scan parameters (min angle, max angle, speed, etc).

`Feedback`<br>
Feedback provides server implementers a way to tell an ActionClient about the incremental progress of a goal. For moving the base, this might be the robot's current pose along the path. For controlling the tilting laser scanner, this might be the time left until the scan completes.

`Result`<br>
A result is sent from the ActionServer to the ActionClient upon completion of the goal. This is different than feedback, since it is sent exactly once. This is extremely useful when the purpose of the action is to provide some sort of information. For move base, the result isn't very important, but it might contain the final pose of the robot. For controlling the tilting laser scanner, the result might contain a point cloud generated from the requested scan.

input:
```
actionlib/
├── action
├── actionlib
├── CHANGELOG.rst
├── CMakeLists.txt
├── docs
├── include
├── mainpage.dox
├── package.xml
├── setup.py
├── src
└── test

```

#### Installation

1.  Download RPM

aarch64:

wget https://117.78.1.88/build/home:davidhan:branches:openEuler:22.03:LTS/standard_aarch64/aarch64/ros-noetic-ros-actionlib/ros-noetic-ros-actionlib-1.13.2-3.oe2203.aarch64.rpm

x86_64:

wget https://117.78.1.88/build/home:davidhan:branches:openEuler:22.03:LTS/standard_x86_64/x86_64/ros-noetic-ros-actionlib/ros-noetic-ros-actionlib-1.13.2-3.oe2203.x86_64.rpm

2.  Install RPM

aarch64:

sudo rpm -ivh ros-noetic-ros-actionlib-1.13.2-3.oe2203.aarch64.rpm --nodeps --force

x86_64:

sudo rpm -ivh ros-noetic-ros-actionlib-1.13.2-3.oe2203.x86_64.rpm --nodeps --force

#### Instructions

Dependence installation

sh /opt/ros/noetic/install_dependence.sh

Exit the following output file under the /opt/ros/noetic/ directory , Prove that the software installation is successful

```
actionlib
├── cmake.lock
├── env.sh
├── include
│   └── actionlib
│       ├── TestActionFeedback.h
│       ├── TestActionGoal.h
│       ├── TestAction.h
│       ├── TestActionResult.h
│       ├── TestFeedback.h
│       ├── TestGoal.h
│       ├── TestRequestActionFeedback.h
│       ├── TestRequestActionGoal.h
│       ├── TestRequestAction.h
│       ├── TestRequestActionResult.h
│       ├── TestRequestFeedback.h
│       ├── TestRequestGoal.h
│       ├── TestRequestResult.h
│       ├── TestResult.h
│       ├── TwoIntsActionFeedback.h
│       ├── TwoIntsActionGoal.h
│       ├── TwoIntsAction.h
│       ├── TwoIntsActionResult.h
│       ├── TwoIntsFeedback.h
│       ├── TwoIntsGoal.h
│       └── TwoIntsResult.h
├── lib
│   ├── actionlib
│   ├── libactionlib.so
│   ├── pkgconfig
│   │   └── actionlib.pc
│   └── python2.7
│       └── dist-packages
├── local_setup.bash
├── local_setup.sh
├── local_setup.zsh
├── setup.bash
├── setup.sh
├── _setup_util.py
├── setup.zsh
└── share
    ├── actionlib
    │   ├── cmake
    │   └── msg
    ├── common-lisp
    │   └── ros
    ├── gennodejs
    │   └── ros
    └── roseus
        └── ros

```

#### Contribution

1.  Fork the repository
2.  Create Feat_xxx branch
3.  Commit your code
4.  Create Pull Request

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