Fetch is sometimes not starting/making progress

[cvoica]

I'd like to ask you for ideas on how to investigate a situation I'm encountering with Fetch().

I create several connections to the NATS server and on each connection I do the following:

• create a durable consumers
• PullSubscribe()
• Fetch 1000 messages with 60s timeout + send the messages to another processing goroutine via a channel
• process those messages + ack

When I start a few connection (e.g. 10) most of the consumers are making progress but a few of them are stuck, the cli command: nats con info shows, for example: Last Delivered Message: Consumer sequence: 0 Stream sequence: 384,706,024

I checked the goroutine stack and it looks to me as Fetch is not getting any messages, it's just stuck
Any ideas how to investigate this?

I use this version
github.com/nats-io/jsm.go v0.0.35
github.com/nats-io/nats.go v1.21.0

[derekcollison]

Best to share a gist of your actual code.

/cc @piotrpio @wallyqs