Wire Tap

A Wire Tap inserts a tee into a channel: it forwards each message to its normal destination and also sends a copy to a secondary channel. This lets you observe traffic — for logging, auditing, monitoring, or analysis — without altering the primary flow or affecting the receiver.

The problem it solves is non-intrusive observation. In production you often need to see what is flowing through a channel for debugging, compliance, or metrics, but you cannot modify producers or consumers and must not change the messages or slow delivery. A wire tap captures a copy transparently.

How It Works

The wire tap is a simple component on the channel that, for every message, performs two sends: one to the original output channel and one to a tap channel. The primary message is unchanged and continues normally. The tapped copy goes to a logger, an audit store, an analytics pipeline, or a debugging tool. Implementations are careful to make the tap side-effect-free and non-blocking so it cannot disturb the main path.

The tap channel may feed a Message Store for durable audit, or a monitoring system that computes throughput and latency. Filters can be applied to tap only messages of interest.

Input --> [Wire Tap] --> Output (unchanged)
                  \--> Tap channel (copy) --> log / audit / analytics

When to Use It

Use it for auditing and compliance, for debugging production flows, for collecting metrics on message traffic, or for feeding a parallel analytics pipeline without touching the main system. It is a standard observability tool in integration frameworks like Camel, which provides a wireTap step.

Avoid tapping sensitive data into less-secure stores; apply content filtering first if needed.

Trade-offs

A wire tap adds duplication and a small amount of overhead per message, and the tap channel needs its own capacity and retention. If the tap is implemented synchronously or can fail, it risks affecting the primary flow, so it should be asynchronous and fault-isolated. Tapped data may include sensitive content, raising privacy and security obligations.

Related Patterns

It often feeds a Message Store for durable audit history. A Message Filter limits which messages are tapped. It relies on copying onto an extra Message Channel and resembles a targeted Publish-Subscribe of selected traffic.

Example

An Apache Camel route uses wireTap("jms:audit") so that every order message continues to the fulfillment service while a copy is sent to an audit queue. A downstream consumer persists those copies, giving compliance a complete, tamper-evident record of all orders processed.