How do I identify which MySQL slave has responded?

I have a MySql Master server replicating to three Slaves.

A legacy website is performing load-balanced Reads from the Slaves.

Is there a method of identifying from the website which of the Slaves is serving a Read request?

I'd prefer a function that I can use to return a server name or ip address as part of the SELECT, but any reasonable met开发者_JAVA百科hod will do.

Thank you in advance.

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 SHOW VARIABLES LIKE 'server_id' 

Each host has to have a own server_id. Should be enough to know which one answered the request.