Failover brokering issue

[YuanYuYuan]

Describe the bug

Even when the failover_brokering option is utilized, transmission failure can still occur due to the disconnection between peers that are connecting to a router.

To reproduce

Topology

flowchart TD
    A(zenohd \n router mode \n tcp/127.0.0.1:7450)
    B(z_pub_modified \n peer mode \n tcp/127.0.0.1:7452)
    C(z_sub \n peer mode \n tcp/127.0.0.1:7451)
    B -- connect --> A
    C -- connect --> A

• Terminal 1

  zenohd -l tcp/127.0.0.1:7450 --no-multicast-scouting

• Terminal 2

  z_sub -m peer -e tcp/127.0.0.1:7450 -l tcp/127.0.0.1:7451 --no-multicast-scouting

• Terminal 3 z_pub_modified.rs, this program closes the transporation between peers after a while.

  
  use std::time::Duration;
  use zenoh::runtime::Runtime;
  use zenoh::config::{whatami::WhatAmI, Config};
  use zenoh::prelude::r#async::*;
  use zenoh::Result;

[async_std::main]

async fn main() -> Result<()> { let connect_endpoint = vec!["tcp/127.0.0.1:7450".parse()?]; let listen_endpoint = vec!["tcp/127.0.0.1:7452".parse()?]; let peer_config = { let mut config = Config::default(); config.set_mode(Some(WhatAmI::Peer)).unwrap(); config.scouting.multicast.set_enabled(Some(false)).unwrap(); config.connect.set_endpoints(connect_endpoint).unwrap(); config.listen.set_endpoints(listen_endpoint).unwrap(); config }; let runtime = Runtime::new(peer_config).await.unwrap(); let _manager = runtime.manager(); let session = zenoh::init(runtime.clone()).res_async().await?; let _receiver = zenoh::scout(WhatAmI::Peer, Config::default()) .res() .await .unwrap();

async_std::task::sleep(Duration::from_secs(1)).await;
dbg!(session
    .info()
    .routers_zid()
    .res_async()
    .await
    .collect::<Vec<ZenohId>>());
dbg!(session
    .info()
    .peers_zid()
    .res_async()
    .await
    .collect::<Vec<ZenohId>>());

for cnt in 0..30 {
    dbg!(runtime.manager().get_transports());
    session.put("demo/example/put", "test").res_async().await?;
    for trans in runtime.manager().get_transports() {
        if 5 <= cnt && cnt <= 10 && trans.get_whatami()? == WhatAmI::Peer {
            trans.close().await?;
        }
    }
    async_std::task::sleep(Duration::from_secs(1)).await;
}
Ok(())

}

### System info

- OS: Arch Linux x86_64
- Kernel: 6.3.1-arch1-1
- CPU: Intel i5-10300H (8) @ 4.500GHz

[OlivierHecart]

Failover brokering has been designed to forward data between peers that cannot directly connect with each other. But it is not able at this time to forward data between peers that can connect to each other but loose connectivity.