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+ collection 4 - An efficient graphing front-end for collectd
+=============================================================
+
+About
+-----
+
+  collection 4 (c4) is a web-based front-end to the RRD files updated by
+  collectd. It is designed to be highly efficient and handle large
+  installations - with 50,000 and more RRD files - well.
+
+
+Concepts
+--------
+
+  Graphs
+  ------
+  c4 lets you configure "graphs" in its config file. Each graph has a selector
+  which determines which files will be used to draw the graph. The selector
+  uses the host/plugin[-instance]/type[-instance] layout known from collectd.
+  Each field of the selector may be one of two wildcard expressions:
+
+    * "/any/"
+      The field may be any value. The files will be grouped by the values of
+      all "/any/" fields. Think of the "GROUP BY" SQL expression. Each grouping
+      is called an "instance" which can be identified by the graph selector and
+      the value of the "/any/" fields.
+
+    * "/all/"
+      As with the any-selector, the field may be any value. However, all files
+      that only differ in the "/all/" field(s) will be printed in the same
+      graph.
+
+  Upon startup, c4 will read the configuration and scan the directory
+  containing the RRD files. Each file is added to all matching graphs, either
+  by adding it to the appropriate instance or by creating a new instance. I.e.
+  each file may be used in multiple graphs.
+
+  If a file does not match any graph, a "dynamic graph" matching only that file
+  will be created. This allows the front-end to display all files even when
+  there is no explicit graph definition for them.
+
+  Data providers
+  --------------
+  The idea is to encapsulate all the functions specific to one write plugin of
+  collectd using an interface for querying data. This allows to program the
+  rest of the front-end in a way that doesn't rely on one specific storage
+  back-end.
+
+  Currently, the only data provider scans a directory for RRD files and uses
+  the librrd to fetch data. The whole concept is still a bit of a work in
+  progress and currently the code-base is still cluttered with "*_get_rrdargs"
+  functions. The RRDtool generated graphs will likely be replaced by a graphing
+  solution integrated in the C code (creating rendered graphics) and / or a
+  JavaScript-based solution which renders graphs in the browser.
+
+
+License
+-------
+
+  collection 4 is licensed under the GNU Lesser General Public License (LGPL),
+  version 2.1. The exact license terms are available in the file "COPYING" in
+  the top source directory.
+
+
+Author
+------
+
+  Florian "octo" Forster <ff at octo.it>
+