How does the Wire Tap EIP work and what is it used for?

The Wire Tap sends a copy of the current message to a secondary endpoint asynchronously while allowing the original message to continue through the route unchanged. It is used for auditing, logging to an append-only store, event sourcing side-channels, and monitoring without adding latency to the main processing path.

from("jms:queue:orders")
    .wireTap("jms:topic:audit-log")   // async copy to audit log
    .to("direct:process-order");         // main flow continues

// Wire tap with body transformation for the copy:
from("direct:payment")
    .wireTap("jms:queue:payment-audit")
        .newExchangeBody(simple("Order ${header.orderId} received at ${date:now:yyyy-MM-dd}"))
    .to("direct:process-payment");

The wire tap sends a shallow copy of the Exchange with a new thread from the routing thread pool. The original Exchange continues immediately — there is no waiting for the tap. In Camel 3.x the tap always uses InOnly semantics; any response from the tap endpoint is discarded. The tap copy shares message headers with the original by default; use newExchangeBody() or onPrepare() to customise the tap message.