Wire Tap

The Wire Tap is a Message Router from Hohpe and Woolf. It sends a copy of the exchange to a tap endpoint for inspection or monitoring while the original exchange continues down the route unchanged.

    let route = RouteBuilder::from("timer:tick?period=1000&repeatCount=5")
        .route_id("wiretap-demo")
        // Tap: send a clone to monitoring (fire-and-forget)
        .wire_tap("log:monitor?showBody=true&showCorrelationId=true")
        // Main pipeline continues normally
        .to("log:main?showBody=true&showCorrelationId=true")
        .build()?;

- id: wiretap-demo
  from: timer:tick?period=1000&repeatCount=5
  steps:
    - wire_tap: log:monitor?showBody=true&showCorrelationId=true
    - to: log:main?showBody=true&showCorrelationId=true

The included route fires a timer and calls .wire_tap("log:monitor?..."). The tap clones the exchange and dispatches the clone to log:monitor, which logs the body and correlation id. The main pipeline then runs the original exchange through .to("log:main?..."), which logs the same body. The tap runs as fire-and-forget. An error on the tap endpoint does not stop the main flow, and the main flow does not wait for the tap to finish.

The Wire Tap differs from Multicast in scope. A wire tap is one side channel. It does not return a value into the main pipeline. The exchange that continues down the route is the same exchange the tap saw before the clone. Multicast is the main flow: it fans out to every branch and aggregates the results back into the pipeline. Use a wire tap to observe an exchange without changing it. Put a consumer on the main pipeline when it must affect the result.

The clone duplicates the body. A wire tap on an exchange with a multi-megabyte body copies that body for the tap endpoint, which costs memory and CPU. For large bodies, pair the route with a Claim Check step that stashes the body and passes a reference id. The tap then reads the reference id without copying the body.

Per ADR-0001, the wire tap compiles into a Service<Exchange> step in the Tower middleware pipeline. The processor contract is documented in camel-processor/CONTEXT.md.

The example source is at examples/wiretap.