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:

> 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
> sudo yum install redis
Python Container
- For instance aragornContainer with the demo CDB

Component Configuration

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

XMLDoc

<?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

#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
> redis-server
Start ACS
Start Python aragornContainer

Send events with ExampleSupplier.py

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

> 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