Symptoms:

• During a new installation or upgrade of vRealize Automation 7.x to 7.4, schema does not load for Machine lifecycle and Machine provisioning event topics within a newly created subscription.
• When opening a new/old Event subscription, the schema definition is blank on the page

VMware vRealize Automation 7.4.x

An empty schema is returned by the Event Broker service when polling to the container service.  The schema actually resides with the IaaS-Proxy-Provider service.

When event broker encounters an external schema event topic, it checks its cache for said schema. If it is there - return it, if not - go check all external schema providers for the given schema ID. We then go on to get a list of all service type IDs and we go through them, one by one, looking if we will get a result for the schema we are looking for (in our case: Infrastructure.EBS.Message.Provision). The first service to return a non-null schema is perceived as the provider of the schema and the schema is put in the cache.

The container-service returned an empty schema, but still returns a schema.

This issue impacts vRealize Automation 7.4 general release environments (no cumulative updates installed).

This issue is resolved in vRealize Automation 7.4 HF5 and greater.  See the following KB for application instructions:  Cumulative Update for vRealize Automation 7.4