Introduction

The Component Caller API is a component that works as a proxy that makes the ACS / CORBA world in a REST API. This enables different functionality, such as connecting standalone applications, plugins and/or web services to the system.

The Event Converter is a component that serves a pre-configured set of events by converting them from ACS' Notification Channel (Based on CORBA's Notification Service) into Redis PubSub model for unreliable subscribers and into Redis queues for reliable subscribers.

At ALMA, these services are being used in a couple of places:

• Integrated Alarms System Plugins to obtaine device information
• ObopsOnlineServer to prepare observation and operational reports (Shift Logs)
• Some prototypes have been done to check feasibility of web services to control the system

Presentation

• Scope
  • Background
  • Component Caller API
  • Event Converter
• Duration: 10 minutes
• ComponentCallerAPI_EventConverter.pdf

Hands-On Exercise

Component Caller API

Deployment / Configuration

• Python Container
  • For instance aragornContainer with the demo CDB
• Component configuration:

...
<e
    Name="ComponentCallerAPI"
    Code="acs.ComponentCallerAPI"
    Type="IDL:alma/ACS/ACSComponent:1.0"
    Container="aragornContainer"
    ImplLang="py"
    Autostart="true"/>
...

Interaction

• Start ACS
• Start a Container

• Interact with a component using curl. For instance to retrieve name and componentState attributes:

  Code Block
  language bash
  > curl -XPOST http://127.0.0.1:9000/ -d'{"componentName": "EventConverter", "methodName": "_get_name", "arguments": {}}' {"data": "EventConverter"} > curl -XPOST http://127.0.0.1:9000/ -d'{"componentName": "EventConverter", "methodName": "_get_componentState", "arguments": {}}' {"data": {"meta": {"type": "omniORB.EnumItem"}, "data": {"_n": "COMPSTATE_OPERATIONAL", "_v": 3, "_parent_id": "IDL:alma/ACS/ComponentStates:1.0"}}}

Event Converter

Deployment / Configuration

• Install redis

  Code Block
  language bash
  > sudo yum install redis

• Python Container
  • For instance aragornContainer with the demo CDB

• Component Configuration

  Code Block
  language xml title CDB/MACI/Components/Components.xml linenumbers true collapse true
  ... <e Name="EventConverter" Code="acs.EventConverter" Type="IDL:alma/ACS/ACSComponent:1.0" Container="aragornContainer" ImplLang="py" Autostart="true"/> ...

• XMLDoc

  Code Block
  language xml title CDB/alma/EventConverter/EventConverter.xml linenumbers true collapse true
  <?xml version="1.0" encoding="ISO-8859-1"?> <EventConverter xmlns="urn:schemas-cosylab-com:EventConverter:1.0" xmlns:baci="urn:schemas-cosylab-com:BACI:1.0" xmlns:cdb="urn:schemas-cosylab-com:CDB:1.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <RedisConn host="localhost" port="6379"/> <PubSub> <Channel name="example"> <EventType type="workshop.ExampleEvent"/> </Channel> </PubSub> <ReliableSubscribers> <Subscriber name="example" queueLimit="20"> <Channel name="example"> <EventType type="workshop.ExampleEvent"/> </Channel> </Subscriber> </ReliableSubscribers> </EventConverter>

• IDL Event Definition

  Code Block
  #ifndef _ExampleEvent_IDL_ #define _ExampleEvent_IDL_ #pragma prefix "alma" module workshop { const string CHANNELNAME_EXAMPLE = "example"; struct ExampleEvent { string msg; long value; }; }; #endif

Interaction

• Start redis-server

  Code Block
  language bash
  > redis-server

• Start ACS
• Start Python aragornContainer

• Send events with ExampleSupplier.py

  Code Block
  import workshop from Acspy.Nc.Supplier import Supplier event = workshop.ExampleEvent("Example Supplier", 10) sup = Supplier(workshop.CHANNELNAME_EXAMPLE) sup.publishEvent(simple_data=event) sup.disconnect()

• Check Redis

  Code Block
  > redis-cli #Get all queues 127.0.0.1:6379> keys * 1) "example" #Check elements of 'example' queue 127.0.0.1:6379> LRANGE example 0 -1 1) "{\"meta\": {\"type\": \"workshop.ExampleEvent\"}, \"data\": {\"msg\": \"Example Supplier\", \"value\": 10}}"

Discussion

• Limitations: Callbacks
• Improvements
• New Ideas