Poll Enrich

The Poll Enrich is a Content Enricher variant from Hohpe and Woolf. It polls a passive resource and feeds the result into the exchange.

    let route = RouteBuilder::from("timer:tick?period=1000&repeatCount=3")
        .route_id("pollenrich-demo")
        .poll_enrich(
            format!("file:{config_dir_str}?fileName=config.json&noop=true"),
            5000,
        )
        .stream_cache_default()
        .to("log:enriched?showBody=true&showHeaders=true&showCorrelationId=true")
        .build()?;

- id: pollenrich-demo
  from: timer:tick?period=1000&repeatCount=3
  steps:
    - poll_enrich:
        uri: "file:/tmp/rust-camel-pollenrich?fileName=config.json&noop=true"
        timeout: 5000
    - stream_cache: true
    - to: log:enriched?showBody=true&showHeaders=true&showCorrelationId=true

The .poll_enrich(uri, timeout) step reads from a polling consumer. It waits up to timeout milliseconds for a message. A file or database is a passive resource. It stores data but does not push it. Poll Enrich pulls that data on demand. The example reads a config file each time the timer fires.

The EnrichmentStrategy trait decides how the polled exchange combines with the original. The default UseEnrichedBody strategy replaces the original body with the polled body. It keeps the original headers and properties. It discards the headers from the polled exchange. Write a custom strategy when you need to merge both bodies or preserve the polled headers.

When the poll returns no message within the timeout, the step calls on_no_poll. The default behavior passes the original exchange through unchanged. ThrowOnNoPoll wraps a base strategy and errors the exchange instead. Use it when missing data is a failure, not a normal condition.

Choose Poll Enrich when the source is a passive consumer. Choose the Content Enricher when the source is an active endpoint that receives a request and returns a response. Poll Enrich reads. Content Enricher calls.

Per ADR-0001, the step compiles into a Service<Exchange> in the Tower pipeline. The strategy contract and the PollEnrichService implementation are documented in camel-processor/CONTEXT.md.

Reference: Processor crate · Example source