Cannot source two streams with the same name from two accounts with flow control

[francoisprunier]

Observed behavior

If I create a stream 'mystreamagg' in account A, that sources stream 'mystream' in account B and stream 'mystream' in account C. Because the streams in account B and accout C have the same name, I cannot configure flow control properly.

A basic config works without flow control works. But because flow control cannot be configured correctly, the sourcing stream can/will be stalled and in practice that means it doesn't work.

Expected behavior

I should be able to configure flow control to work when both streams have the same name. Note that it works if they have different names because the FC subject contain the stream name.

Potential solution to fix it: If I could prefix the FC subjects like I do with the JS API when defining a stream source

{
  "name": "mystreamagg",
 (...)
  "sources": [
    {
      "name": "mystream",
      "external": {
        "api": "JS.B.API",
        "fc": "JS.B.FC",
        "deliver": "deliver.b.mystream"
      }
    },
    {
      "name": "mystream",
      "external": {
        "api": "JS.C.API",
        "fc": "JS.C.FC",
        "deliver": "deliver.c.mystream"
      }
    }
  ],
  (...)
}

then I'd be able to import the FC subjects from both accounts under a different name and it would all work.

Server and client version

Server: 2.10.25
Client: 0.1.6

Host environment

No response

Steps to reproduce

Here's a basic server config:

port: 4222
server_name: my-server
jetstream {
    store_dir="./store_server"
}
accounts {
    SYS: {
        users: [{user: admin, password: admin}]
    },
    A: {
        users: [{user: a, password: pass}],
        jetstream: enabled
        imports: [
            {service: {account: B, subject: "$JS.API.CONSUMER.CREATE.mystream"}, to: "JS.B.API.CONSUMER.CREATE.mystream"}
            {service: {account: C, subject: "$JS.API.CONSUMER.CREATE.mystream"}, to: "JS.C.API.CONSUMER.CREATE.mystream"}
            {stream: {account: B, subject: deliver.b.mystream.>}}
            {stream: {account: C, subject: deliver.c.mystream.>}}
	    # Cannot do the imports below (for good reason)
	    # {service: {account: B, subject: "$JS.FC.mystream.>"}
	    # {service: {account: C, subject: "$JS.FC.mystream.>"}
        ]
    }
    B: {
        users: [{user: b, password: pass}],
        jetstream: enabled
        exports: [
            {service: "$JS.API.CONSUMER.CREATE.mystream", response_type: "stream"}
            {stream: "deliver.b.mystream.>"}
            {service: "$JS.FC.mystream.>"}
        ]
    }
    C: {
        users: [{user: c, password: pass}],
        jetstream: enabled
        exports: [
	    {service: "$JS.API.CONSUMER.CREATE.mystream", response_type: "stream"}
	    {stream: "deliver.c.mystream.>"}
	    {service: "$JS.FC.mystream.>"}
	]
    }
}
system_account: SYS

And the aggregate stream:

{
  "name": "mystreamagg",
  "retention": "limits",
  "max_consumers": -1,
  "max_msgs_per_subject": 0,
  "max_msgs": -1,
  "max_bytes": -1,
  "max_age": 0,
  "max_msg_size": -1,
  "storage": "file",
  "discard": "old",
  "num_replicas": 1,
  "duplicate_window": 120000000000,
  "sources": [
    {
      "name": "mystream",
      "external": {
        "api": "JS.B.API",
        "deliver": "deliver.b.mystream"
      }
    },
    {
      "name": "mystream",
      "external": {
        "api": "JS.C.API",
        "deliver": "deliver.c.mystream"
      }
    }
  ],
  "sealed": false,
  "deny_delete": false,
  "deny_purge": false,
  "allow_rollup_hdrs": false,
  "allow_direct": true,
  "mirror_direct": false,
  "consumer_limits": {}
}

The streams in B and C are just normal streams.