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| <h2>ZeroConf (Zero Configuration)</h2> |
| <p>One of the hardest parts of any network-based application is configuring which bits connect to what, and how |
| do they connect to each other. Each device that can be connected <emphasis>to</emphasis> already knows |
| the configuration details required to connect to it, but every other device that may wish to connect to it |
| will need to be provided with this information so the connection can be established. |
| </p> |
| <p> |
| ZeroConf aims to eliminate the time-consuming aspect of connecting devices together. The device broadcasts the |
| configuration details reqired to connect or work with the service over a multicast protocol. You probably already have |
| devices on your local network such as printers that are automatically discovered by your computer. |
| </p> |
| <p> |
| Zeroconf is an open-standard that many vendors are using to reduce cost of configuration. The <b>JmDNS</b> project |
| is an Apache 2.0 licensed library that implements the ZeroConf protocol. Chainsaw and log4j use |
| JmDNS to broadcast Appender information so that a matching Receiver can be easily created to connect to each other |
| to stream logging messages into Chainsaw. |
| </p> |
| <p> |
| <ul> |
| <li><a href="http://www.zeroconf.org" target="_new">http://www.zeroconf.org</a></li> |
| <li><a href="http://jmdns.sf.net" target="_new">http://jmdns.sf.net</a></li> |
| </ul> |
| </p> |
| <h2>Interesting... So what do I need to use ZeroConf with Chainsaw & log4j?</h2> |
| <p> |
| Most of the network-based appenders are ZeroConf-capable - all you have to do to use ZeroConf is to |
| download the JmDNS package (at least version 1.0), add the JmDNS jar to your application's classpath, and set the "advertiseViaMulticastDNS" |
| parameter to 'true' for any of the appenders or receivers you want to advertise (most of the time you will want to advertise appenders, so they can be |
| automatically detected by Chainsaw).</p> |
| <p>You're log4j.xml configuration file could be as simple as this:</p> |
| <pre> |
| <log4j:configuration debug="false" threshold="debug" xmlns:log4j="http://jakarta.apache.org/log4j/> |
| <appender name="zeroconf" class="org.apache.log4j.net.SocketHubAppender"> |
| <param name="Name" value="MyZeroConfSockeHubAppender" /> |
| <param name="advertiseViaMulticastDNS" value="true" /> |
| </appender> |
| <!--ROOT Logger--> |
| <root> |
| <level value="INFO" /> |
| <appender-ref ref="zeroconf" /> |
| </root> |
| </log4j:configuration> |
| </pre> |
| <p> |
| Once you have started your application using this configuration, from within Chainsaw, the ZeroConf tab will show detected |
| applications. You can simply double click on the detected appender and Chainsaw will connect a Receiver to it. You can even tick the "Auto-Connect" |
| check box, and next time Chainsaw see's this application, it will automatically connect to it. |
| </p> |
| <p>Most of the network-based Receivers are also ZeroConf capable, giving ZeroConf-aware appenders or applications |
| the ability to discover the receivers and configure appenders to connect to those Receivers. |
| </p> |
| <h2>Cool... But I have some applications that use log4j 1.2.x. Will it still work?</h2> |
| <p>Yes. We have designed a backward compatible mechanism to expose prior versions of log4j's SocketHubAppender (ZeroConfSocketHubAppender) |
| so that Chainsaw can detect it automatically. |
| </p> |
| |
| <h2>But... Surely there's a catch?</h2> |
| <p>A small catch. Because it's based on a multicast protocol, routers tend to block these packets, and so it's likely that your production computers, |
| which are usually in a heavily protected network won't be able to broadcast their configuration information. If you have a VPN |
| into this sort of network it is possible that these multicast packets can traverse the network.</p> |
| |
| <h2>Oh... So is this even useful?</h2> |
| <p>It's extremely useful for development, QA and staging environments. Usually the QA/Staging environment is isolated from your development |
| team, but having them monitor logs from these machines would be handy. Or your QA team may want to copy/paste some ERROR messages from |
| QA/staging to notify the dev team. ZeroConf gives your whole software development team an easy way to get access to your logging events.</p> |
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