Struct InboundMessage 

#[non_exhaustive]
pub struct InboundMessage {
    pub header: Bytes,
    pub payload: Bytes,
    pub guard: InFlightGuard,
}

An inbound MessageType::Message frame together with the in-flight guard that makes it visible to ShutdownState::wait_for_drain.

The guard is mandatory, which is the whole point of the type: a message cannot sit on the inbound queue without being counted work. Producers never build one directly — TransportAdapter::admit_message acquires the guard and constructs it, and the message channel’s sender is private so there is no other way in. Whatever happens to the message afterwards — dispatched, dropped on a decode error, handed back undelivered when the receiver has gone, discarded by a consumer that is abandoning its backlog at teardown — the guard rides along and its Drop releases the count. “Queued implies counted” is therefore an invariant of the type system, not a convention producers have to honour.

The one thing that does not release a guard is walking away from the channel: flume frees buffered items only once the last endpoint is gone, so a consumer that stops receiving while transports still hold sender clones must drain and drop what it is abandoning, not merely drop its receiver.

#[non_exhaustive]: construct with InboundMessage::new, match with a trailing ...

Fields (Non-exhaustive)

Non-exhaustive structs could have additional fields added in future. Therefore, non-exhaustive structs cannot be constructed in external crates using the traditional Struct { .. } syntax; cannot be matched against without a wildcard ..; and struct update syntax will not work.

header: Bytes

The frame’s header bytes.

payload: Bytes

The frame’s payload bytes.

guard: InFlightGuard

Keeps the instance’s in-flight count non-zero for as long as this message exists, queued or in a handler.

Implementations

impl InboundMessage

pub fn new(header: Bytes, payload: Bytes, guard: InFlightGuard) -> Self

Bind a frame to an already-acquired in-flight guard.

Public for consumer-side fabrication — a test that wants a realistic item to feed a receiver, or a harness that stands in for the runtime. It is not a way onto the inbound queue: the channel’s sender is private, so producers still go through TransportAdapter::admit_message.