Add outbound MQTT factor

Co-authored-by: rylev <[email protected]>
Signed-off-by: karthik2804 <[email protected]>

crates/factor-outbound-mqtt/Cargo.toml

@@ -0,0 +1,24 @@
+[package]
+name = "spin-factor-outbound-mqtt"
+version = { workspace = true }
+authors = { workspace = true }
+edition = { workspace = true }
+
+[dependencies]
+anyhow = "1.0"
+rumqttc = { version = "0.24", features = ["url"] }
+spin-factor-outbound-networking = { path = "../factor-outbound-networking" }
+spin-factors = { path = "../factors" }
+spin-core = { path = "../core" }
+spin-world = { path = "../world" }
+tracing = { workspace = true }
+table = { path = "../table" }
+tokio = { version = "1.0", features = ["sync"] }
+
+[dev-dependencies]
+spin-factor-variables = { path = "../factor-variables" }
+spin-factors-test = { path = "../factors-test" }
+tokio = { version = "1", features = ["macros", "rt"] }
+
+[lints]
+workspace = true

crates/factor-outbound-mqtt/src/host.rs

@@ -0,0 +1,131 @@
+use std::{sync::Arc, time::Duration};
+
+use anyhow::Result;
+use spin_core::{async_trait, wasmtime::component::Resource};
+use spin_factor_outbound_networking::OutboundAllowedHosts;
+use spin_world::v2::mqtt::{self as v2, Connection, Error, Qos};
+use tracing::{instrument, Level};
+
+pub type CreateClient = Arc<
+    dyn Fn(String, String, String, Duration) -> Result<Box<dyn MqttClient>, Error> + Send + Sync,
+>;
+
+pub struct InstanceState {
+    pub allowed_hosts: OutboundAllowedHosts,
+    pub connections: table::Table<Box<dyn MqttClient>>,
+    pub create_client: CreateClient,
+}
+
+impl InstanceState {
+    pub fn new(allowed_hosts: OutboundAllowedHosts, create_client: CreateClient) -> Self {
+        Self {
+            allowed_hosts,
+            create_client,
+            connections: table::Table::new(1024),
+        }
+    }
+}
+
+#[async_trait]
+pub trait MqttClient: Send + Sync {
+    async fn publish_bytes(&self, topic: String, qos: Qos, payload: Vec<u8>) -> Result<(), Error>;
+}
+
+impl InstanceState {
+    async fn is_address_allowed(&self, address: &str) -> Result<bool> {
+        self.allowed_hosts.check_url(address, "mqtt").await
+    }
+
+    async fn establish_connection(
+        &mut self,
+        address: String,
+        username: String,
+        password: String,
+        keep_alive_interval: Duration,
+    ) -> Result<Resource<Connection>, Error> {
+        self.connections
+            .push((self.create_client)(
+                address,
+                username,
+                password,
+                keep_alive_interval,
+            )?)
+            .map(Resource::new_own)
+            .map_err(|_| Error::TooManyConnections)
+    }
+
+    async fn get_conn(&self, connection: Resource<Connection>) -> Result<&dyn MqttClient, Error> {
+        self.connections
+            .get(connection.rep())
+            .ok_or(Error::Other(
+                "could not find connection for resource".into(),
+            ))
+            .map(|c| c.as_ref())
+    }
+}
+
+impl v2::Host for InstanceState {
+    fn convert_error(&mut self, error: Error) -> Result<Error> {
+        Ok(error)
+    }
+}
+
+#[async_trait]
+impl v2::HostConnection for InstanceState {
+    #[instrument(name = "spin_outbound_mqtt.open_connection", skip(self, password), err(level = Level::INFO), fields(otel.kind = "client"))]
+    async fn open(
+        &mut self,
+        address: String,
+        username: String,
+        password: String,
+        keep_alive_interval: u64,
+    ) -> Result<Resource<Connection>, Error> {
+        if !self
+            .is_address_allowed(&address)
+            .await
+            .map_err(|e| v2::Error::Other(e.to_string()))?
+        {
+            return Err(v2::Error::ConnectionFailed(format!(
+                "address {address} is not permitted"
+            )));
+        }
+        self.establish_connection(
+            address,
+            username,
+            password,
+            Duration::from_secs(keep_alive_interval),
+        )
+        .await
+    }
+
+    /// Publish a message to the MQTT broker.
+    ///
+    /// OTEL trace propagation is not directly supported in MQTT V3. You will need to embed the
+    /// current trace context into the payload yourself.
+    /// https://w3c.github.io/trace-context-mqtt/#mqtt-v3-recommendation.
+    #[instrument(name = "spin_outbound_mqtt.publish", skip(self, connection, payload), err(level = Level::INFO),
+        fields(otel.kind = "producer", otel.name = format!("{} publish", topic), messaging.operation = "publish",
+        messaging.system = "mqtt"))]
+    async fn publish(
+        &mut self,
+        connection: Resource<Connection>,
+        topic: String,
+        payload: Vec<u8>,
+        qos: Qos,
+    ) -> Result<(), Error> {
+        let conn = self.get_conn(connection).await.map_err(other_error)?;
+
+        conn.publish_bytes(topic, qos, payload).await?;
+
+        Ok(())
+    }
+
+    fn drop(&mut self, connection: Resource<Connection>) -> anyhow::Result<()> {
+        self.connections.remove(connection.rep());
+        Ok(())
+    }
+}
+
+pub fn other_error(e: impl std::fmt::Display) -> Error {
+    Error::Other(e.to_string())
+}

crates/factor-outbound-mqtt/src/lib.rs

@@ -0,0 +1,128 @@
+mod host;
+
+use std::time::Duration;
+
+use host::other_error;
+use host::CreateClient;
+use host::InstanceState;
+use rumqttc::{AsyncClient, Event, Incoming, Outgoing, QoS};
+use spin_core::async_trait;
+use spin_factor_outbound_networking::OutboundNetworkingFactor;
+use spin_factors::{
+    ConfigureAppContext, Factor, InstanceBuilders, PrepareContext, RuntimeFactors,
+    SelfInstanceBuilder,
+};
+use spin_world::v2::mqtt::{self as v2, Error, Qos};
+use tokio::sync::Mutex;
+
+pub use host::MqttClient;
+
+pub struct OutboundMqttFactor {
+    create_client: CreateClient,
+}
+
+impl OutboundMqttFactor {
+    pub fn new(create_client: CreateClient) -> Self {
+        Self { create_client }
+    }
+}
+
+impl Factor for OutboundMqttFactor {
+    type RuntimeConfig = ();
+    type AppState = ();
+    type InstanceBuilder = InstanceState;
+
+    fn init<T: Send + 'static>(
+        &mut self,
+        mut ctx: spin_factors::InitContext<T, Self>,
+    ) -> anyhow::Result<()> {
+        ctx.link_bindings(spin_world::v2::mqtt::add_to_linker)?;
+        Ok(())
+    }
+
+    fn configure_app<T: RuntimeFactors>(
+        &self,
+        _ctx: ConfigureAppContext<T, Self>,
+    ) -> anyhow::Result<Self::AppState> {
+        Ok(())
+    }
+
+    fn prepare<T: RuntimeFactors>(
+        &self,
+        _ctx: PrepareContext<Self>,
+        builders: &mut InstanceBuilders<T>,
+    ) -> anyhow::Result<Self::InstanceBuilder> {
+        let allowed_hosts = builders
+            .get_mut::<OutboundNetworkingFactor>()?
+            .allowed_hosts();
+        Ok(InstanceState::new(
+            allowed_hosts,
+            self.create_client.clone(),
+        ))
+    }
+}
+
+impl SelfInstanceBuilder for InstanceState {}
+
+pub struct NetworkedMqttClient {
+    inner: rumqttc::AsyncClient,
+    event_loop: Mutex<rumqttc::EventLoop>,
+}
+
+const MQTT_CHANNEL_CAP: usize = 1000;
+
+impl NetworkedMqttClient {
+    pub fn create(
+        address: String,
+        username: String,
+        password: String,
+        keep_alive_interval: Duration,
+    ) -> Result<Self, Error> {
+        let mut conn_opts = rumqttc::MqttOptions::parse_url(address).map_err(|e| {
+            tracing::error!("MQTT URL parse error: {e:?}");
+            Error::InvalidAddress
+        })?;
+        conn_opts.set_credentials(username, password);
+        conn_opts.set_keep_alive(keep_alive_interval);
+        let (client, event_loop) = AsyncClient::new(conn_opts, MQTT_CHANNEL_CAP);
+        Ok(Self {
+            inner: client,
+            event_loop: Mutex::new(event_loop),
+        })
+    }
+}
+
+#[async_trait]
+impl MqttClient for NetworkedMqttClient {
+    async fn publish_bytes(&self, topic: String, qos: Qos, payload: Vec<u8>) -> Result<(), Error> {
+        let qos = match qos {
+            Qos::AtMostOnce => rumqttc::QoS::AtMostOnce,
+            Qos::AtLeastOnce => rumqttc::QoS::AtLeastOnce,
+            Qos::ExactlyOnce => rumqttc::QoS::ExactlyOnce,
+        };
+        // Message published to EventLoop (not MQTT Broker)
+        self.inner
+            .publish_bytes(topic, qos, false, payload.into())
+            .await
+            .map_err(other_error)?;
+
+        // Poll event loop until outgoing publish event is iterated over to send the message to MQTT broker or capture/throw error.
+        // We may revisit this later to manage long running connections, high throughput use cases and their issues in the connection pool.
+        let mut lock = self.event_loop.lock().await;
+        loop {
+            let event = lock
+                .poll()
+                .await
+                .map_err(|err| v2::Error::ConnectionFailed(err.to_string()))?;
+
+            match (qos, event) {
+                (QoS::AtMostOnce, Event::Outgoing(Outgoing::Publish(_)))
+                | (QoS::AtLeastOnce, Event::Incoming(Incoming::PubAck(_)))
+                | (QoS::ExactlyOnce, Event::Incoming(Incoming::PubComp(_))) => break,
+
+                (_, _) => continue,
+            }
+        }
+        Ok(())
+    }
+}