Adding a module for system health monitoring (getting graphs generated by rrdtool

of usual system counters).
It sets up some cron jobs for collecting the data, and not that often, generating the
graphs. Then the httpd server is configured with a directory with the generated
static files.

http://www.brianlane.com/software/systemhealth/

svn path=/nixos/trunk/; revision=18866

modules/module-list.nix

@@ -60,6 +60,7 @@
   ./services/misc/synergy.nix
   ./services/monitoring/monit.nix
   ./services/monitoring/nagios/default.nix
+  ./services/monitoring/systemhealth.nix
   ./services/monitoring/zabbix-agent.nix
   ./services/monitoring/zabbix-server.nix
   ./services/network-filesystems/nfs-kernel.nix

modules/services/monitoring/systemhealth.nix

@@ -0,0 +1,130 @@
+{config, pkgs, ...}:
+
+with pkgs.lib;
+
+let
+  cfg = config.services.systemhealth;
+
+  systemhealth = with pkgs; stdenv.mkDerivation {
+    name = "systemhealth-1.0";
+    src = fetchurl {
+      url = "http://www.brianlane.com/software/systemhealth/src/systemhealth-1.0.tar.bz2";
+      sha256 = "1q69lz7hmpbdpbz36zb06nzfkj651413n9icx0njmyr3xzq1j9qy";
+    };
+    buildInputs = [ python ];
+    installPhase = ''
+      ensureDir $out/bin
+      cp system_health.py $out/bin
+    '';
+  };
+
+  rrdDir = "/var/lib/health/rrd";
+  htmlDir = "/var/lib/health/html";
+
+  configFile = rrdDir + "/.syshealthrc";
+  # The program will try to read $HOME/.syshealthrc, so we set the proper home.
+  command = "HOME=${rrdDir} ${systemhealth}/bin/system_health.py";
+
+  cronJob = ''
+    */5 * * * * wwwrun ${command} --log
+    5 * * * * wwwrun ${command} --graph
+  '';
+
+  nameEqualName = s: "${s} = ${s}";
+  interfacesSection = concatStringsSep "\n" (map nameEqualName cfg.interfaces);
+
+  driveLine = d: "${d.path} = ${d.name}";
+  drivesSection = concatStringsSep "\n" (map driveLine cfg.drives);
+
+in
+{
+  options = {
+    services.systemhealth = {
+      enable = mkOption {
+        default = false;
+        description = ''
+          Enable the system health monitor and its generation of graphs.
+        '';
+      };
+
+      urlPrefix = mkOption {
+        default = "/health";
+        description = ''
+          The URL prefix under which the System Health web pages appear in httpd.
+        '';
+      };
+
+      interfaces = mkOption {
+        default = [ "lo" ];
+        example = [ "lo" "eth0" "eth1" ];
+        description = ''
+          Interfaces to monitor (minimum one).
+        '';
+      };
+
+      drives = mkOption {
+        default = [ ];
+        example = [ { name = "root"; path = "/"; } ];
+        description = ''
+          Drives to monitor.
+        '';
+      };
+    };
+  };
+
+  config = mkIf cfg.enable {
+    services.cron.systemCronJobs = [ cronJob ];
+
+    system.activationScripts.systemhealth = fullDepEntry ''
+      mkdir -p ${rrdDir} ${htmlDir}
+      chown wwwrun.wwwrun ${rrdDir} ${htmlDir}
+
+      cat >${configFile} << EOF
+      [paths]
+      rrdtool = ${pkgs.rrdtool}/bin/rrdtool
+      loadavg_rrd = loadavg
+      ps = /var/run/current-system/sw/bin/ps
+      df = /var/run/current-system/sw/bin/df
+      meminfo_rrd = meminfo
+      uptime_rrd = uptime
+      rrd_path = ${rrdDir}
+      png_path = ${htmlDir}
+
+      [processes]
+
+      [interfaces]
+      ${interfacesSection}
+
+      [drives]
+      ${drivesSection}
+
+      [graphs]
+      width = 400
+      time = ['-3hours', '-32hours', '-8days', '-5weeks', '-13months']
+      height = 100
+
+      [external]
+
+      EOF
+
+      chown wwwrun.wwwrun ${configFile}
+
+      ${pkgs.su}/bin/su -s "/bin/sh" -c "${command} --check" wwwrun
+      ${pkgs.su}/bin/su -s "/bin/sh" -c "${command} --html" wwwrun
+    '' [ "var" ];
+
+    services.httpd.extraSubservices = [
+      { function = f: {
+          extraConfig = ''
+            Alias ${cfg.urlPrefix} ${htmlDir}
+            
+            <Directory ${htmlDir}>
+                Order allow,deny
+                Allow from all
+            </Directory>
+          '';
+        };
+      }
+    ];
+  };
+}