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postal.addWireTap
description: adds a wiretap to the message bus. The wiretap is a callback that is invoked when any message is published. It is often useful for logging and/or debugging purposes, but should not be used where a normal SubscriptionDefinition
would be sufficient. Extending postal through add-ons, however, might be a valid use-case for a non-logging/non-diagnostics wire tap. The postal.federation base plugin for federating postal instances (between iframes/workers, for example, with postal.xframe) utilizes wire taps in order to collect messages to be sent to the remote instance(s) of postal.
returns: an anonymous function that can be used to remove the wiretap (by invoking it).
A wiretap callback can take up to two arguments:
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data
- the data (message body) of the published message -
envelope
- the full envelope of the published message, which may include up to:-
channel
- the channel name (string) -
topic
- the topic (string) -
timeStamp
- the date/time the message was published -
data
- the value of the published message (message body)
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Example Usage:
var tap = postal.addWireTap( function( d, e ) {
console.log( JSON.stringify( e ) );
});
// later, to remove the wiretap
tap();
Be sure to check out the postal.diagnostics add-on, which takes advantage of wire tap functionality.