Hybrid Communication

[owny990312]

Describe the feature

1.Is it possible to use zenoh for both shared memory communication and network cross-machine communication?Does it currently have such basic functionality? 2.Can it even autonomously schedule which solution to use? Thanks

[YuanYuYuan]

Hi @owny990312! Yes, Zenoh has already supported this functionality. Assuming you have three zenoh sessions assigned as below, you can check the messages are successfully transmitted.

flowchart TB
    subgraph Machine1["Machine 1"]
        A["Publisher"]
        B["Subscriber 1"]
        A -- SHM --> B
    end
    subgraph Machine2["Machine 2"]
        C["Subscriber 2"]
    end
    A -- TCP --> C

• Machine 1

  ./z_pub_shm
  ./z_sub_shm

• Machine 2

  ./z_sub_shm

[owny990312]

Hi @owny990312! Yes, Zenoh has already supported this functionality. Assuming you have three zenoh sessions assigned as below, you can check the messages are successfully transmitted.嗨！是的，Zenoh 已经支持这项功能。假设你有三个 zenoh 会话，如下所示，你可以检查消息是否成功传输。

flowchart TB
    subgraph Machine1["Machine 1"]
        A["Publisher"]
        B["Subscriber 1"]
        A -- SHM --> B
    end
    subgraph Machine2["Machine 2"]
        C["Subscriber 2"]
    end
    A -- TCP --> C

• Machine 1 机器 1

./z_pub_shm
./z_sub_shm

• Machine 2 机器 2

./z_sub_shm

Thank you for your answer.

I'd like to further confirm: I just use the shm-API for all cases, then it will automatically handle network communication for cross-machine scenarios while using shared memory for local machine communication.

Could you point me to any relevant documentation?

[owny990312]

Hi @owny990312! Yes, Zenoh has already supported this functionality. Assuming you have three zenoh sessions assigned as below, you can check the messages are successfully transmitted.嗨！是的，Zenoh 已经支持这项功能。假设你有三个 zenoh 会话，如下所示，你可以检查消息是否成功传输。

flowchart TB
    subgraph Machine1["Machine 1"]
        A["Publisher"]
        B["Subscriber 1"]
        A -- SHM --> B
    end
    subgraph Machine2["Machine 2"]
        C["Subscriber 2"]
    end
    A -- TCP --> C

• Machine 1 机器 1

./z_pub_shm
./z_sub_shm

• Machine 2 机器 2

./z_sub_shm

I did some testing and the results were very exciting.

I'd like to know how the internal judgment is made.

Also, during execution, since I'm using the shm-API but actually receiving cross-machine data, is this error a normal phenomenon? Will it affect the speed?

[YuanYuYuan]

Hi @owny990312, Thanks for reporting this. I've created an issue for it, #814. Don't worry; this doesn't affect performance.

The mechanism of zenoh deciding whether to send the buffer with SHM depends on the underlying link while it's established. You can check the details here https://github.com/eclipse-zenoh/zenoh/blob/e73a89d3bab5d3960159ddfc0ef315407d2fdf7e/io/zenoh-transport/src/shm.rs?plain=1#L123