streamling sink plugin — Agent Skill

A sink consumes RecordBatches at the tail of a pipeline and writes them to an external system (a database, queue, object store, webhook). Sinks receive an upstream schema, do heavy I/O, and must preserve exactly-once semantics through the checkpoint protocol.

Prerequisite: streamling-plugin-basics (crate setup, registration, lifecycle, errors).

The trait

#[async_trait]
pub trait SinkPlugin: SupportsGracefulShutdown + Send + Sync {
    async fn initialize(&self) -> Result<(), PluginError>;
    fn labels(&self) -> Vec<PluginLabel> { Vec::new() }            // optional identity
    async fn process_batch(&self, data: RecordBatch) -> Result<(), PluginError>;
    async fn process_checkpoint_marker(&self, epoch: CheckpointEpoch) -> Result<(), PluginError>;
    async fn process_checkpoint_finalizer(&self, epoch: CheckpointEpoch) -> Result<(), PluginError>;
}