Congestion Control

Zenoh provides per-publisher congestion control to handle scenarios where a subscriber cannot keep up with the publication rate.

Modes

Mode	Behaviour
`Drop`	Drop the message if the channel is full (default)
`Block`	Block the publisher until the channel drains

let publisher = session
    .declare_publisher("sensors/camera/frames")
    .congestion_control(CongestionControl::Drop)
    .await?;

Priority

Zenoh supports 8 priority levels for message scheduling:

use zenoh::publication::Priority;
 
let publisher = session
    .declare_publisher("control/emergency")
    .priority(Priority::RealTime)   // highest priority
    .await?;

Priority	Value	Use case
`RealTime`	1	Safety-critical control
`InteractiveHigh`	2	User interactions
`InteractiveLow`	3	UI updates
`DataHigh`	4	Sensor data
`Data`	5	Default
`DataLow`	6	Bulk transfer
`Background`	7	Logging

Express Mode

For ultra-low latency, disable fragmentation and batching:

let publisher = session
    .declare_publisher("control/motor")
    .express(true)
    .await?;