Struct ClientBuilder 

pub struct ClientBuilder<T> {
    transport: T,
    options: ClientOptions,
    persistence: SessionPersistence,
    command_channel_capacity: usize,
    message_channel_capacity: usize,
}

Builder for an MqttClient.

Obtain one with MqttClient::builder, set the persistence backend and channel capacities, then call start:

use finmqtt_tokio::transport::TcpTransport;
use finmqtt_tokio::{ClientOptions, FilePersistence, MqttClient};

let (owner, client, messages) = MqttClient::builder(
    TcpTransport::new("broker.example.com", 1883),
    ClientOptions::new("my-client".parse().unwrap()).reconnect(),
)
.persistence(FilePersistence::new("session.journal"))
.command_channel_capacity(512)
.start()
.await?;

Fields

transport: T

options: ClientOptions

persistence: SessionPersistence

command_channel_capacity: usize

message_channel_capacity: usize

Implementations

impl<T: Transport + Send + Sync + 'static> ClientBuilder<T>

pub(crate) const fn new(transport: T, options: ClientOptions) -> Self

Creates a builder with default wiring and no persistence.

pub fn persistence(self, persistence: impl Into<SessionPersistence>) -> Self

Sets how the session is durably persisted across restarts.

Pass a backend builder: FilePersistence for a journal file, or TursoPersistence (with the turso feature) for a turso database. Defaults to no persistence.

pub const fn command_channel_capacity(self, capacity: usize) -> Self

Sets the command channel capacity (default DEFAULT_COMMAND_CHANNEL_CAPACITY).

Bounds how many publish/subscribe/unsubscribe commands may be queued before callers must await; raising it trades memory for burst tolerance.

pub const fn message_channel_capacity(self, capacity: usize) -> Self

Sets the inbound message channel capacity (default DEFAULT_MESSAGE_CHANNEL_CAPACITY).

Bounds how many received messages buffer for the MessageStream before backpressure pauses inbound reads.

pub async fn start(self) -> Result<(EventLoopHandle, MqttClient, MessageStream)>

Starts the client, loading any persisted session first.

Returns the EventLoopHandle that owns the spawned event loop, the client handle, and the MessageStream of incoming PUBLISH messages. The event loop runs as long as the EventLoopHandle lives; keep it and call stop for a graceful shutdown. This method returns immediately; the first connection attempt happens in the background. To block until the broker accepted the connection, await connection_status(). wait_until_connected() on the returned client.

Errors

Returns an I/O error if the persistence backend cannot be opened or its persisted state cannot be loaded.