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</style><title>Differences from FAM</title></head><body bgcolor="#8b7765" text="#000000" link="#a06060" vlink="#000000"><table border="0" width="100%" cellpadding="5" cellspacing="0" align="center"><tr><td width="120"></td><td><table border="0" width="90%" cellpadding="2" cellspacing="0" align="center" bgcolor="#000000"><tr><td><table width="100%" border="0" cellspacing="1" cellpadding="3" bgcolor="#fffacd"><tr><td align="center"><h1>Gamin the File Alteration Monitor</h1><h2>Differences from FAM</h2></td></tr></table></td></tr></table></td></tr></table><table border="0" cellpadding="4" cellspacing="0" width="100%" align="center"><tr><td bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td valign="top" width="200" bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="1" width="100%" bgcolor="#000000"><tr><td><table width="100%" border="0" cellspacing="1" cellpadding="3"><tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Main Menu</b></center></td></tr><tr><td bgcolor="#fffacd"><ul><li><a href="index.html">Home</a></li><li><a href="overview.html">Overview</a></li><li><a href="using.html">Using gamin</a></li><li><a href="config.html">Configuration</a></li><li><a href="news.html">News</a></li><li><a href="downloads.html">Downloads</a></li><li><a href="python.html">Python bindings</a></li><li><a href="devel.html">Developers informations</a></li><li><a href="contacts.html">Contacts</a></li><li><a href="FAQ.html">FAQ</a></li><li><a href="debug.html">Debugging Gamin</a></li><li><a href="security.html">Security</a></li><li><a href="internals.html">Internals</a></li><li><a href="differences.html">Differences from FAM</a></li><li><a href="ChangeLog.html">ChangeLog</a></li></ul></td></tr></table><table width="100%" border="0" cellspacing="1" cellpadding="3"><tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Related links</b></center></td></tr><tr><td bgcolor="#fffacd"><ul><li><a href="http://mail.gnome.org/archives/gamin-list/">Mail archive</a></li><li><a href="http://oss.sgi.com/projects/fam/">FAM project</a></li><li><a href="sources/">sources</a></li><li><a href="http://bugzilla.gnome.org/buglist.cgi?product=gamin">GNOME Bugzilla</a></li><li><a href="https://bugzilla.redhat.com/bugzilla/buglist.cgi?product=Fedora+Core">Red Hat Bugzilla</a></li></ul></td></tr></table></td></tr></table></td><td valign="top" bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="1" width="100%"><tr><td><table border="0" cellspacing="0" cellpadding="1" width="100%" bgcolor="#000000"><tr><td><table border="0" cellpadding="3" cellspacing="1" width="100%"><tr><td bgcolor="#fffacd"><h3>Differences</h3><p>gamin should be binary and source code compatible with FAM 2.6.8.
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However there are some differences and at least one significant
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extension.</p><p>The differences are in term of implementation:</p><ul><li>No system wide server, instead it relies on per user server, if
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needed started on demand by the fam/gamin library.</li>
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<li>The functions FAMSuspendMonitor(), FAMResumeMonitor() and
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FAMMonitorCollection() are not implemented. They all raise problem
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of accumulating unbounded state on the server side and better handled
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at the client level if needed.</li>
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<li>FAMErrno is provided, but the values may not match their FAM
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counterparts, similary FamErrlist[] error messages are different.</li>
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<li>No NFS support based on specific RPC and server, instead gamin monitors
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only the state as reported locally by the kernel, not that locally done
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changes on NFS or AFS filesystems are reported on Linux which is the
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main criteria when having user home directories on such filesystems.</li>
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</ul><h3>Extension(s)</h3><p>We tried to limit changes in gamin but a number of features were
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deemed more important than sticking to the exact same set than FAM:</p><ul><li>Support for inotify on Linux if compiled in the kernel, this override
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most of the deficiencies related to dnotify.</li>
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<li>A lot of debugging support was added both for client and server
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see the <a href="debug.html">specific page</a> on the matter.</li>
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<li>The possibility to block Exist/EndExists callbacks when monitoring
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directories based on a new API, see below</li>
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</ul><p>FAM when monitoring a directory, immediately send a set of events
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listing the files found in that directory, this ends up with an EndExists
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events. However when monitoring hierarchy it's usually far more efficient
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and simple to do the scanning on the client side and ignore those
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directory listing events from the FAM server (the only drawback is a potential
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mismatch of the directory content between the FAM server and the client).
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In such a case, all those events are not only superfluous but they are
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also dangerous since they can lead to a congested pipe to the client
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which is just scanning directories and not listening to FAM. To that
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intent we added in gamin 0.0.23 a new API disabling the Exists/EndExists
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sequences when watching directories for a given FAMConnection:</p><pre>int FAMNoExists(FAMConnection *fc)</pre><p>and with the Python bindings:</p><pre>WatchMonitor.no_exists()</pre><p>This feature is also used when the client reconnect to the server
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after a connection loss or if the server died.</p><p>Calling it changes the protocol as described below, directory
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monitoring from that call will only get mutation events and not
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the initial lists:</p><p><img src="callbacks.gif" alt="The NoExists behaviour change on callbacks" /></p><p><a href="contacts.html">Daniel Veillard</a></p></td></tr></table></td></tr></table></td></tr></table></td></tr></table></td></tr></table></body></html>
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