--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/rrdweb/backend.py	Tue Jan 25 01:28:06 2011 +0200
@@ -0,0 +1,92 @@
+from rrdweb import rrd
+
+import operator
+
+def host_def (idx, name, dir, ds_in, ds_out, cf) :
+    """
+        VDEFs for given host, giving its avg/max values:
+
+            DEF:in/out_{idx}
+            CDEFtraf_{idx}
+            VDEF:avg/max_{idx}
+            PRINT:{idx} avg/max {value}
+    """
+
+    params = dict(
+        dir=dir, ds_in=ds_in, ds_out=ds_out, cf=cf,
+        idx=idx, rrd='%s/%s.rrd' % (dir, name)
+    )
+
+    return [
+        # in/out bandwidth in bytes/s
+        'DEF:in_%(idx)d=%(rrd)s:%(ds_in)s:%(cf)s' % params,
+        'DEF:out_%(idx)d=%(rrd)s:%(ds_out)s:%(cf)s' % params,
+
+        # total traffic in bits/s
+        'CDEF:traf_%(idx)d=in_%(idx)d,out_%(idx)d,+,8,*' % params,
+
+        # average + maximum values
+        'VDEF:avg_%(idx)d=traf_%(idx)d,AVERAGE' % params,
+        'VDEF:max_%(idx)d=traf_%(idx)d,MAXIMUM' % params,
+
+        # output
+        'PRINT:avg_%(idx)d:%(idx)d avg %%lf' % params,
+        'PRINT:max_%(idx)d:%(idx)d max %%lf' % params,
+    ]
+
+def parse_report (rrds, lines) :
+    """
+        Parse the report output into a [ (name, avg, max) ] list
+    """
+
+    # idx values by type
+    data = {
+        'avg': {},
+        'max': {},
+        }
+
+    # interpret output
+    for line in lines :
+        # parse
+        idx, type, value = line.split()
+        
+        # convert
+        idx = int(idx)
+        value = float(value)
+        
+        # store
+        data[type][idx] = value
+    
+    # build into name : (values) dict
+    return [
+        (
+            (name, data['avg'][idx], data['max'][idx])
+        ) for idx, name in enumerate(rrds)
+    ]
+
+def calc_top_hosts (dir, rrds, ds_in, ds_out, period='15m', count=5, cf='AVERAGE') :
+    """
+        Return the list of top-N rrd's in the given dir, sorted by total in/out bandwidth average over the given period.
+    """
+
+    # vdefs for hosts, avg/max_<idx> in bits/s + prints
+    defs = [stmt for idx, name in enumerate(rrds) for stmt in host_def(idx, name, dir, ds_in, ds_out, cf)]
+    
+    # execute
+    _, _, output, _ = rrd.graph(False, *defs, start=('-%s' % period))
+    
+    # parse
+    data = parse_report(rrds, output)
+
+    # sort for top-N avg
+    data.sort(key=operator.itemgetter(1))
+    top_avg = data[:count]
+
+    # sort for top-N max
+    data.sort(key=operator.itemgetter(2))
+    top_max = data[:count]
+
+    # merge hosts (we lose sorting order)
+    return set(host for host, avg, max in top_avg + top_max)
+
+