1. C++ Tango REST API implementation
Joint Institute for Nuclear Research, Dubna, Russia
RestDS –
C++ Tango REST API implementation
Georgy Sedykh, Evgeny Gorbachev
TANGO ICALEPCS 2017

2. Web clients 1. Web technologies progress 2. Advantages: Universal
Flixible
Well-looking
Convenient
Universal tools for communication between Tango Controls and Web clients are required

3. REST Global identification of resources (URL);
REST (Representational State Transfer) – architectural principles to design web services that focus on system’s resources.
Global identification of resources (URL);
Manipulation of resources through the standard protocol (HTTP);
Stateless;

4. Tango REST API RC4 * Describes how to:
Operate with different tango hosts;
Browse Tango units (devices, attributes, properties, commands, pipes);
Write/Read attributes;
Execute commands;
Write/Read pipes;
Get/Set properties;
Use authentication mechanisms;
Transmit arguments as http parameters;
Parse Response JSON;
Use Error codes;
Attribute
Command
Pipe
Property
REST Service URL
REST API Version
Tango host
Tango device ID *

5. RestDS
– Tango module, designed to provide access to tango control system units through http requests;
Features:
Developed in C++ with Boost and OpenSSL;
Windows and Linux supported;
Lightweight;
Tango device server;
Both http and https protocols supported;
Basic http authentication supported;
Uses server-side role-based Tango access control and logging system (More info: TUPHA171 – Development of NICA Control System: Access Control and Logging);
Git:
Tango REST API RC4 partial support (so far without pipes);

6. RestDS :: Examples To read attribute:
GET http(s)://host:port/tango/rest/rc4/devices/domain/family/member/attributes/name/value
To write attribute:
POST / PUT http(s)://host:port/tango/rest/rc4/devices/domain/family/member/attributes/name
+ arguments as POST parameters.
To execute command without arguments:
POST / PUT http(s)://host:port/tango/rest/rc4/devices/domain/family/member/commands/name
To execute command with arguments:
POST / PUT http(s)://host:port/tango/rest/rc4/devices/domain/family/member/commands/name
+ arguments as POST parameters.

7. Response as JSON object if success Or http error code if failed..
RestDS :: Operation diagram
Web Client
RestDS
HTTP code OK
Response as JSON object if success
Host:port
Threads number
Authentication
Security (SSL) {
“name”: “T56”,
“quality”: “VALID”,
“timestamp”: ,
“value”: , }
Or http error code if failed..
400 – Bad request 403 – Forbidden
401 – Unauthorized 404 – Not found

8. Web client examples :: Thermometry

9. Web client examples :: Satellite refrigerators control

10. Summary:
Web client applications are cross-platform, well-looking and convenient;
Web clients will be widely distributed within the NICA Control system.
RestDS Tango module was developed to provide universal way to communicate between web client and Tango-based control system.