title: Is it slow to publish to no subscribers relative to one subscriber with ZeroMQ?
body: <h2><strong>Is it significantly slower to publish<br>when there is one subscriber v/s no subscribers at all?</strong></h2>
  
  <pre><code>More Detail:
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  <p>We're writing a <strong><code>ZeroMQ</code></strong> application, where speed is very important.<br><Br>We have many nodes that communicate via <strong><code>REQ/REP</code></strong> as well as <strong><code>PUB/SUB</code></strong> and the network automatically selects <strong><code>{ ipc: | tcp: }</code></strong> transport-class, if the nodes are on the same machine.</p>
  
  <p>We'd like to sometimes log the messages between certain nodes. With <code>PUB/SUB</code> this is easy, we just have a "logging node" subscribed to the publisher. However, with <code>REQ/REP</code>, we cannot read the request/response without becoming a proxy or otherwise slowing down the connection.</p>
  
  <p>We're considering having all of the nodes using <code>REQ/REP</code> publish to a unique TCP address every time they send a message ( so each node has a "logging address" that they send all their messages to ), we'll then just subscribe to the "logging addresses" we're interested in, if we want to log.</p>
  
  <pre><code>Question:
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  <p>Will we suffer a performance penalty if we ARE NOT subscribed to the "logging address"? A slowdown during logging is okay, but performance penalties during normal operation are not desirable.</p>