Create all FlowExporter resources in a function

[heanlan]

Describe what you are trying to solve
In antrea/cmd/antrea-agent/agent.go, we create denyConnStore, conntrackConnStore, flowExporter separately. We can try to have a function in flowexporter package to create all the flowexporter resources. Reference to: #2360 (comment)

Describe the solution you have in mind
As there are a lot of variables required by NewConntrackConnectionStore(), NewFlowExporter(), we might consider to group some of the variables, in order to avoid to pass too many parameters to the creating-resources function.

[srikartati]

This is not a major change that warrants an issue IMO. Please open a PR directly or have a TODO in the code in your next PR.

[heanlan]

This is not a major change that warrants an issue IMO. Please open a PR directly or have a TODO in the code in your next PR.

Got it. I thought issue can be used as a TODO, now be more aware of the usage of issues. Thanks!

[antoninbas]

It's fine to open an issue if you are not sure sure about the change (and wants to discuss it) or if you don't have time to tackle it in the near future.

[heanlan]

It's fine to open an issue if you are not sure sure about the change (and wants to discuss it) or if you don't have time to tackle it in the near future.

Got it. Thanks Antonin.

[heanlan]

There is a problem - if we want to create all the resources in a function under flowexporter package, there will be some import cycles: between flowexporter and connections package, between flowexporter and priorityqueue package.
e.g. we need to call methods in connections package in line, while connections package imports flowexporter in line.

Do we have any solutions to handle the import cycle problems? @antoninbas @srikartati

[srikartati]

In antrea/cmd/antrea-agent/agent.go, we create denyConnStore, conntrackConnStore, flowExporter separately. We can try to have a function in flowexporter package to create all the flowexporter resources. Reference to: #2360 (comment)

How can denyConnStore is grouped with conntrackConnStore? denyConnStore is needed for initialization of networkPolicyController, and networkPolicyController is needed for conntrackConnStore.

[heanlan]

In antrea/cmd/antrea-agent/agent.go, we create denyConnStore, conntrackConnStore, flowExporter separately. We can try to have a function in flowexporter package to create all the flowexporter resources. Reference to: #2360 (comment)

How can denyConnStore is grouped with conntrackConnStore? denyConnStore is needed for initialization of networkPolicyController, and networkPolicyController is needed for conntrackConnStore.

I'm thinking we can declare denyConnStore this variable before we initialize networkPolicyController, and actually assign value for this variable in the function we want to create, not sure whether that would work or not...

[srikartati]

I'm thinking we can declare denyConnStore this variable before we initialize networkPolicyController, and actually assign value for this variable in the function we want to create, not sure whether that would work or not...

I think as a first step, combining priority queue and connection store initializations separately for denyConnStore and conntrackConnStore is better. You could try placing those in the connections package.

[heanlan]

I think as a first step, combining priority queue and connection store initializations separately for denyConnStore and conntrackConnStore is better. You could try placing those in the connections package.

Yes, the first step makes a lot of sense. I have done that in the PR.
If we want a step further, i think at least we cannot wrap all into the current flowexporter package, due to the import cycle problems. I'll try to think about anything else we can do.