Computes CPU states every 5 seconds in the system interface

scripts/lua/modules/system_utils.lua

@@ -5,18 +5,146 @@
 local dirs = ntop.getDirs()
 package.path = dirs.installdir .. "/scripts/lua/modules/?.lua;" .. package.path
 
-require "lua_utils"
-
 local json = require("dkjson")
 
 local system_utils = {}
 
 -- #################################
 
+local CPU_STATES_PREV_KEY = "ntopng.cache.system_utils.cpu_states.prev"
+local CPU_STATES_DELTA    = "ntopng.cache.system_utils.cpu_states.delta"
+
+-- #################################
+
+-- Save cpu_states (either a delta or an absolute value) in a redis key.
+-- The format used is the same as the one used by /proc/stat
+local function save_cpu_states(cpu_states, key)
+   -- To serialize CPU states use the same format as the one used in /proc/stat
+   -- This allows us to re-use the parse function both to read serialized values as well as to read the line directly from /proc/stat
+
+   local cpu_line = string.format("cpu %u %u %u %u %u %u %u %u %u %u",
+				  cpu_states["user"] or 0, cpu_states["nice"] or 0, cpu_states["system"] or 0,
+				  cpu_states["idle"] or 0, cpu_states["iowait"] or 0, cpu_states["ira"] or 0,
+				  cpu_states["softirq"] or 0, cpu_states["steal"] or 0, cpu_states["guest"] or 0,
+				  cpu_states["guest_nice"] or 0)
+
+   ntop.setCache(key, cpu_line, 120 --[[ 2 minutes --]])
+end
+
+-- #################################
+
+-- Reads a line with the format of /proc/stat and parses the various state values into a table
+local function parse_proc_stat_cpu_line(cpu_line)
+   -- Parse the cpu string using an sscanf-like pattern
+   local user, nice, system, idle, iowait, irq, softirq, steal, guest, guest_nice = cpu_line:match("cpu%s+(%d+)%s+(%d+)%s+(%d+)%s+(%d+)%s+(%d+)%s+(%d+)%s+(%d+)%s+(%d+)%s+(%d+)%s+(%d+)")
+
+   local states = {
+      user = user or 0, nice = nice or 0, system = system or 0,
+      idle = idle or 0, iowait = iowait or 0, irq = irq or 0,
+      softirq = softirq or 0, steal = steal or 0, guest = guest or 0,
+      guest_nice = guest_nice or 0
+   }
+
+   return states
+end
+
+-- #################################
+
+-- Computes the delta of the current cpu states submitted in cur_states
+-- with their previous values
+local function compute_cpu_states_delta(cur_states)
+   -- Read the previously saved line so it can be compared with the cur_states
+   -- to compute the variation
+   local prev_cpu_line = ntop.getCache(CPU_STATES_PREV_KEY)
+   local states_delta = {}
+
+   -- It there was a previous line...
+   if prev_cpu_line and prev_cpu_line ~= "" then
+      -- Parse the previous line in its corresponding previous states
+      local prev_states = parse_proc_stat_cpu_line(prev_cpu_line)
+
+      -- Now iterate the current states and compute their deltas with reference
+      -- to their previous value
+      for cur_state, cur_val in pairs(cur_states) do
+	 local cur_delta = 0
+
+	 if prev_states[cur_state] then
+	    cur_delta = cur_val - prev_states[cur_state]
+
+	    -- Safety check
+	    if cur_delta < 0 then
+	       cur_delta = 0
+	    end
+	 end
+
+	 states_delta[cur_state] = math.floor(cur_delta) -- make sure it's an integer
+      end
+
+      -- Save the deltas
+      save_cpu_states(states_delta, CPU_STATES_DELTA)
+   end
+
+   -- Save the current cpu states in the prev key so they will automatically
+   -- become previous during the next call
+   save_cpu_states(cur_states, CPU_STATES_PREV_KEY)
+
+   return states_delta
+end
+
+-- #################################
+
+function system_utils.compute_cpu_states()
+   if not ntop.isWindows() then
+      local f = io.open("/proc/stat", "r")
+
+      if f then
+	 -- The first line of the file contains cpu time_spent
+	 -- See http://man7.org/linux/man-pages/man5/proc.5.html for the meaning of each column
+	 local cpu_line = f:read("*line")
+
+	 if cpu_line and cpu_line ~= "" then
+	    local cur_states = parse_proc_stat_cpu_line(cpu_line)
+	    local states_delta = compute_cpu_states_delta(cur_states)
+	 end
+
+	 f:close()
+      end
+   end
+end
+
+-- #################################
+
+-- Returns all the available cpu states in %
+function system_utils.get_cpu_states()
+   local states_delta_line = ntop.getCache(CPU_STATES_DELTA)
+
+   if states_delta_line and states_delta_line ~= "" then
+      -- Parse the delta in its corresponding states
+      local delta_states = parse_proc_stat_cpu_line(states_delta_line)
+
+      local total = 0
+      for _, delta_val in pairs(delta_states) do
+	 total = total + delta_val
+      end
+
+      -- Express in percentage
+      for state in pairs(delta_states) do
+	 if total > 0 then
+	    delta_states[state] = delta_states[state] / total * 100
+	 else
+	    delta_states[state] = 0
+	 end
+      end
+
+      return delta_states
+   end
+end
+
+-- #################################
+
 function system_utils.systemHostStats()
    local system_host_stats =  ntop.systemHostStat()
-
-   -- TODO: add CPU states stats generated by cpu_states_monitor.lua
+   system_host_stats["cpu_states"] = system_utils.get_cpu_states()
 
    return system_host_stats
 end