We are facing a cyclic dependency error (Module.error.cyclicDependencies) while starting openmrs intermittently in the current build of Bahmni. It happens once-in-a-while which is puzzling. When this issue happened, we tried to debug this issue by placing one omod at a time and restarted openmrs. We saw that it happens with providermanagement omod.
The following are some of the questions unanswered:
Why does it happen intermittently and not always.
When it happens, we try to restore the database to a previously working dump and openmrs starts up without any issue. How is this related to the database dump? Do we store any state in database about previous failures of openmrs.
The following are the versions of openmrs modules we use:
The server log is available here… Please refer to the line 103. Please note that the messages about invalid omod extensions (.omod1) was renamed intentionally just to ensure that the modules are not loaded for debugging the problem.
Unfortunately this section of code seems to be eating some information. @bharatak, are you in a position to run OpenMRS in a debugger with a breakpoint at ModuleFactory:256 and share info about the CycleException?
@lluismf i think this section of code needs to be reworked a bit because of the following reasons:
A module is no longer able to start if any of the modules it is aware of is not started. This should not be so.
When this CycleException is thrown, all modules fail to start. Before this change, modules that have all dependencies started, would start well. And those which fail to start would display an error message with a list of dependant modules that are not started. We no longer have these error messages and hence cannot easily tell why a module failed to start.
For an example of how to reproduce a CycleException, create a dummy module that is aware of these modules:
Load this in the reference application and then stop the REST webservices module. On restarting openmrs, you should get this Module.error.cyclicDependencies where edges has this: [emrapi->dummymodule, appframework->dummymodule, appui->dummymodule]
I assumed the dependencies were not cyclic and used Kahn’s algorithm described here:
But if cycles are allowed the algorithm is no longer valid (it’s for DAG only). Do we really want to allow cycles? This implies that if cycles are found a node in the cycle must be picked randomly. It doesn’t seem right.