Make sure IPs are only sent once when sending to ArrayPort on a subgraph

[kenhkan]

When sending to a subgraph, the same IP is sent to the subgraph the same number of times as how many processes are attached to an open ArrayPort. Something like:

subgraph.fbp:

Merge(Merge) OUT -> IN Output(Output) 

main_graph.fbp:

'subgraph.fbp' -> IN Graph(Graph)
'a' -> MERGE.IN Graph()
'b' -> MERGE.IN Graph()
'c' -> MERGE.IN Graph()

The above should print:

a
b
b
c
c
c

This seems to be due to using ArrayPort-to-ArrayPort attachment to make a link between the graph and the subgraph. Sending the IP only to the first socket solves the problem as all the sockets point to the same process in the subgraph anyway.

[travisbot]

This pull request passes (merged ff09619 into 5f4fcfa).

[kenhkan]

Just a clarification. The above currently prints:

a
b
b
c
c
c

where it should print:

a
b
c

[travisbot]

This pull request passes (merged 7f68b38 into 5f4fcfa).

[kenhkan]

I have this crazy thought... Would this problem persist if the whole noflo is implemented asynchronously? Say:

'SomeInitial' -> IN A(Something) OUT -> IN B(Graph) OUT -> IN C(SomethingElse)

In the current implementation, 'SomeInitial' is sent to A and then sent to B immediately. If data flow is async, wouldn't B setting up be run before 'SomeInitial' is passed to it, making the ports to be available for attachment between A and B?

[kenhkan]

See #42

[bergie]

Thanks for the PR! I'm mostly offline this week in Istanbul, so I'll be able to look at these in details next week

[bergie]

@kenhkan sorry about taking my time with these. This pull req doesn't apply cleanly any longer, unfortunately. Can you rebase and push so it gets updated?

[kenhkan]

@bergie Humorously the same thing happened to me. I was in Vietnam for several weeks so I'm sorry that I couldn't comment any earlier.

#41 should not be an issue if #42 is fixed. It's two solutions to the same problem. Well, #42 is a more complete solution. I'm closing this now.