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. In the future it shall be possible to use multiple data providers in parallel. The vision is to have multiple servers running RRDCacheD. Data is distributed to those servers using the "Hashed" match of collectd and then a unified interface is provided via c4. Dependencies ------------ c4 currently requires the following libraries: * libfcgi * librrd_th (thread-safe version of librrd) * libyajl The "configure" script is currently kept minimal. It may therefore be necessary to set the CPP- and LD-flags manually. In case of libyajl, which is not built with libtool, you may need to set the rpath, too. Bugs ---- * Sending a FLUSH command to the collectd process is not yet possible. * "*_get_rrdargs" functions and other RRDtool specific cruft is still all over the code-base. * The JSON-based interface is unstable. * Currently it's not possible to display more than one graph at a time. (With a very limited and undocumented exception.) * Speaking of which: There is no documentation. * No default page. -> Redirect to "list_graphs" action. * ... (to be added) 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. c4 includes the JavaScript library "jQuery" which is dual-licensed under the MIT license and the GPL. The file "share/jquery-1.4.2.min.js" includes a license header which points you to more detailed information. c4 includes the JavaScript libraries "Raphaël" and "gRaphaël" which are licensed under the MIT license. The files "share/raphael-min.js", "share/g.raphael-min.js", and "share/g.line-min.js" each include a license header which points you to more detailed information. Author ------ Florian "octo" Forster