1 collection 4 - An efficient graphing front-end for collectd
2 =============================================================
4 About
5 -----
7 collection 4 (c4) is a web-based front-end to the RRD files updated by
8 collectd. It is designed to be highly efficient and handle large
9 installations - with 50,000 and more RRD files - well.
12 Concepts
13 --------
15 Graphs
16 ------
17 c4 lets you configure "graphs" in its config file. Each graph has a selector
18 which determines which files will be used to draw the graph. The selector
19 uses the host/plugin[-instance]/type[-instance] layout known from collectd.
20 Each field of the selector may be one of two wildcard expressions:
22 * "/any/"
23 The field may be any value. The files will be grouped by the values of
24 all "/any/" fields. Think of the "GROUP BY" SQL expression. Each grouping
25 is called an "instance" which can be identified by the graph selector and
26 the value of the "/any/" fields.
28 * "/all/"
29 As with the any-selector, the field may be any value. However, all files
30 that only differ in the "/all/" field(s) will be printed in the same
31 graph.
33 Upon startup, c4 will read the configuration and scan the directory
34 containing the RRD files. Each file is added to all matching graphs, either
35 by adding it to the appropriate instance or by creating a new instance. I.e.
36 each file may be used in multiple graphs.
38 If a file does not match any graph, a "dynamic graph" matching only that file
39 will be created. This allows the front-end to display all files even when
40 there is no explicit graph definition for them.
42 Data providers
43 --------------
44 The idea is to encapsulate all the functions specific to one write plugin of
45 collectd using an interface for querying data. This allows to program the
46 rest of the front-end in a way that doesn't rely on one specific storage
47 back-end.
49 Currently, the only data provider scans a directory for RRD files and uses
50 the librrd to fetch data. The whole concept is still a bit of a work in
51 progress and currently the code-base is still cluttered with "*_get_rrdargs"
52 functions. The RRDtool generated graphs will likely be replaced by a graphing
53 solution integrated in the C code (creating rendered graphics) and / or a
54 JavaScript-based solution which renders graphs in the browser.
56 In the future it shall be possible to use multiple data providers in
57 parallel. The vision is to have multiple servers running RRDCacheD. Data is
58 distributed to those servers using the "Hashed" match of collectd and then a
59 unified interface is provided via c4.
62 Dependencies
63 ------------
65 c4 currently requires the following libraries:
67 * libfcgi
68 <http://www.fastcgi.com/>
70 * librrd_th (thread-safe version of librrd)
71 <http://oss.oetiker.ch/rrdtool/>
73 * libyajl
74 <http://lloyd.github.com/yajl/>
76 The "configure" script is currently kept minimal. It may therefore be
77 necessary to set the CPP- and LD-flags manually. In case of libyajl, which is
78 not built with libtool, you may need to set the rpath, too.
81 Bugs
82 ----
84 * Sending a FLUSH command to the collectd process is not yet possible.
85 * "*_get_rrdargs" functions and other RRDtool specific cruft is still all
86 over the code-base.
87 * The JSON-based interface is unstable.
88 * Currently it's not possible to display more than one graph at a time.
89 (With a very limited and undocumented exception.)
90 * Speaking of which: There is no documentation.
91 * No default page. -> Redirect to "list_graphs" action.
92 * ... (to be added)
95 License
96 -------
98 collection 4 is licensed under the GNU Lesser General Public License (LGPL),
99 version 2.1. The exact license terms are available in the file "COPYING" in
100 the top source directory.
102 c4 includes the JavaScript library "jQuery" which is dual-licensed under the
103 MIT license and the GPL. The file "share/jquery-1.4.2.min.js" includes a
104 license header which points you to more detailed information.
106 c4 includes the JavaScript libraries "Raphaël" and "gRaphaël" which are
107 licensed under the MIT license. The files "share/raphael-min.js",
108 "share/g.raphael-min.js", and "share/g.line-min.js" each include a license
109 header which points you to more detailed information.
112 Author
113 ------
115 Florian "octo" Forster <ff at octo.it>