Bug 815899

Description of problem:
The issue is that latest configuration update might be out of sync with the resource configuration directly referenced from the resource.

The consequences are quite severe. The resource configuration returned from the remote API calls is empty until there is an explicit user-initiated update of the resource configuration or the agent detects an out-of-band configuration update.

This happens if the configuration of the resource is viewed from the GUI prior to the first configuration report for the resource being sent up from the agent (which is by default 15 minutes after import).

Version-Release number of selected component (if applicable):
4.4.0-SNAPSHOT

How reproducible:
always

Steps to Reproduce:
1. Import RHQ Agent or any resource with non-empty resource configuration
2. Directly after import, go to its configuration tab. Check that it contains correct configuration properties.
3. In CLI, do:
ProxyFactory.getResource(<RESOURCE_ID_OF_THE_IMPORTED_RESOURCE).resourceConfiguration.properties
4. Alternatively in the CLI do:
ConfigurationManager.getResourceConfiguration(<RESOURCE_ID_OF_THE_IMPORTED_RESOURCE>).properties
  
Actual results:
The CLI claims that the configuration has "0 rows", i.e. no properties, which is in direct contrast to what can be seen using the GUI

Expected results:
CLI returns the same configuration as can be seen in the GUI

Additional info:
My initial investigation suggests that the culprit for this bug is ConfigurationManagerBean.getLatestResourceConfigurationUpdate() (line 359) which at a point calls (at line 427) persistNewAgentReportedResourceConfiguration() (line 466) method (which does persist an update in the configuration history but merely sets the resource configuration on the resource (line 489), leaving it upon the callers to merge the resource in (or let the entity manager do that on transaction commit). After the persistNewAgentReportedResourceConfiguration() has been called, getLatestResourceConfigurationUpdate() then checks (line 443) if there has been any changes reported by the persistNewAgentReportedResourceConfiguration() and if there were, it DISCARDS any pending changes in the entityManager by calling entityManager.clear() (line 451).

This in effect prevents the resource configuration to be set to a correct value by any future configuration report from the agent up to the point where the configuration actually changes either by user-initiated update through RHQ or by agent detecting a change. This is because in ConfigurationServerServiceImpl.persistUpdatedResourceConfiguration() we return eagerly if we detect that the configuration hasn't changed from the last known update (which was successfully persisted by the above call-chain, unlike the reference to the current resource configuration from the resource itself).