Smart Proxy

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A pair of Wire Taps can be used to track messages that flow through a component. However, this approach assumes that the component publishes messages to a fixed output channel. However, many service-style components publish reply messages to the channel specified by the Return Address included in the request message.

How can you track messages on a service that publishes reply messages to the Return Address specified by the requestor?

Use a Smart Proxy to store the Return Address supplied by the original requestor and replace it with the address of the Smart Proxy. When the service sends the reply message route it to the original Return Address.

The Smart Proxy intercepts messages sent on the request channel to the Request-Reply service. For each incoming message, the Smart Proxy stores the Return Address specified by the original sender. It then replaces the Return Address in the message with the channel the reply channel that the Smart Proxy is listening on. When a reply message comes in on that channel, the Smart Proxy retrieves the stored Return Address and uses a Message Router to forward the unmodified reply address to that channel.

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Related patterns: Correlation Identifier, Message Router, Request-Reply, Return Address, Wire Tap


Enterprise Integration Patterns Find the full description of this pattern in:
Enterprise Integration Patterns
Gregor Hohpe and Bobby Woolf
ISBN 0321200683
650 pages
Addison-Wesley
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