How about a slightly different architecture:

  1. Create a table, visible in all namespaces called Requests - and from Data Source namespace add 1 row to it on every new message.
  2. Create a table, visible in all namespaces called Ack which contains {RequestId, Namespace, State}
  3. In each namespace create a Business Service which would:
    1. Poll Requests/Ack tables to get new unprocessed requests (no corresponding Ack record).
    2. If an unprocessed request is found create an Ack record and send a message in a local namespace for BP processing
    3. Maybe write a response after the message is processed (or do it in BP/ProxyBP/job)

Advantage of this architecture is that you decouple processing on a namespace level - so if a production in one namespace is in error state/down the rest can proceed. It also eliminates a single point of failure in namespace switching job.
 

tl;dr instead of pushing your event make consumers pull it whenever convenient.

OnHandleCorsRequest is called automatically if a browser requests CORS.

To add to original answer a bit:

Do %response.SetHeader("Access-Control-Allow-Origin","*")

This is OK for development but for production use you need to replace * with a hostname of your web site.

First of all I would recommend reading these two documents available on WRC (Software Distribution - Docs):

  • InterSystems IRIS Adoption Guide
  • InterSystems IRIS In Place Conversion Guide

First one explains the differences between Cache and InterSystems IRIS and the second one is about automated in-place conversion from Cache to InterSystems IRIS.

I would recommend the following steps:

  • upgrade to 2016.2
    • This is the place to uplift your application - on the one hand it's still Cache so upgrade is simple, on the other the code, even with the new 2016.2 features would probably run fine on InterSystems IRIS
    • if you're using SQL - start using frozen plans
    • if you're using JSON - new JSON features become available here (dynamic objects)
  • upgrade to 2018.1 (latest micro)
  • perform in-place conversion to the latest InterSystems IRIS

On Windows execute:

<iris>\bin\irisdb -s <iris>\mgr

where <iris> is a root of an InterSystems IRIS installation.