Fixed free memory measurements, cache and buffers are still free memory as far as we are concerned

modules/nagios/files/check_memory

 #!/usr/bin/env python
 
 import re, argparse
 
 def format_memory(bytes):
   if bytes >= 1024 * 1024:
     return "%i MB" % (bytes / (1024 * 1024))
   elif bytes >= 1024:
     return "%i kB" % (bytes / 1024)
   else:
     return "%i bytes"
 
 if __name__ == "__main__":
   parser = argparse.ArgumentParser(description="Determine the amount of available memory")
   parser.add_argument("--physical-warn", dest="memwarn", type=int, default=-1, help="Warning threshold for available physical memory (in percent)")
   parser.add_argument("--physical-critical", dest="memcrit", type=int, default=-1, help="Critical threshold for available physical memory (in percent)")
   parser.add_argument("--swap-warn", dest="swapwarn", type=int, default=-1, help="Warning threshold for available swap memory (in percent)")
   parser.add_argument("--swap-critical", dest="swapcrit", type=int, default=-1, help="Critical threshold for available swap memory (in percent)")
   args = parser.parse_args()
 
-  memtotal = None
-  memfree = None
-  swaptotal = None
-  swapfree = None
+  meminfo = {}
   with open("/proc/meminfo", "r") as file:
     for line in file:
       label, value = line.split(None, 1)
 
       label = label.lower().rstrip(":")
       value = value.strip()
       match = re.match(r"^(\d+)\s+(kb|mb|gb)$", value, re.IGNORECASE)
       if match:
         value = int(match.group(1)) * 1024
         if match.group(2).lower() != "kb":
           value *= 1024
           if match.group(2).lower() != "mb":
             value *= 1024
       else:
         value = int(value)
+      meminfo[label] = value
 
-      if label == "memtotal":
-        memtotal = value
-      elif label == "memfree":
-        memfree = value
-      elif label == "swaptotal":
-        swaptotal = value
-      elif label == "swapfree":
-        swapfree = value
+  memtotal = meminfo.get("memtotal", 0)
+  memfree = meminfo.get("memfree", 0) + meminfo.get("buffers", 0) + meminfo.get("cached", 0)
+  swaptotal = meminfo.get("swaptotal", 0)
+  swapfree = meminfo.get("swapfree", 0) + meminfo.get("swapcached", 0)
 
   mempercentage = round(float(memfree) / memtotal * 100)
   swappercentage = round(float(swapfree) / swaptotal * 100)
 
   status = "memory %i%% (%s/%s) swap %i%% (%s/%s)" % (
     mempercentage, format_memory(memfree), format_memory(memtotal),
     swappercentage, format_memory(swapfree), format_memory(swaptotal)
   )
 
   perfdata = "memory=%i;%i;%i swap=%i;%i;%i" % (
     mempercentage, args.memwarn, args.memcrit,
     swappercentage, args.swapwarn, args.swapcrit
   )
 
   output = "%s|%s" % (status, perfdata)
 
   if mempercentage <= args.memcrit or swappercentage <= args.swapcrit:
     print "CRITICAL - " + output
   elif mempercentage <= args.memwarn or swappercentage <= args.swapwarn:
     print "WARNING - " + output
   else:
     print "OK - " + output