IH-543: Add IPMI DCMI based power reading rrdd plugin

Guard against buggy firmware by ignoring 0 or 65535 Watts
(although xcp-rrdd doesn't actually correctly ignore these yet).

Future-proof plugin by parsing Watts as float, although currently
it is always an integer in the DCMI spec.

Signed-off-by: Edwin Török <[email protected]>

Makefile

@@ -202,6 +202,7 @@ install: build doc sdk doc-json
 	install -D -m 755 _build/install/default/bin/xcp-rrdd-iostat $(DESTDIR)$(LIBEXECDIR)/xcp-rrdd-plugins/xcp-rrdd-iostat
 	install -D -m 755 _build/install/default/bin/xcp-rrdd-squeezed $(DESTDIR)$(LIBEXECDIR)/xcp-rrdd-plugins/xcp-rrdd-squeezed
 	install -D -m 755 _build/install/default/bin/xcp-rrdd-xenpm $(DESTDIR)$(LIBEXECDIR)/xcp-rrdd-plugins/xcp-rrdd-xenpm
+	install -D -m 755 _build/install/default/bin/xcp-rrdd-dcmi $(DESTDIR)$(LIBEXECDIR)/xcp-rrdd-plugins/xcp-rrdd-dcmi
 	install -D -m 644 ocaml/xcp-rrdd/bugtool-plugin/rrdd-plugins.xml $(DESTDIR)$(ETCXENDIR)/bugtool/xcp-rrdd-plugins.xml
 	install -D -m 644 ocaml/xcp-rrdd/bugtool-plugin/rrdd-plugins/stuff.xml $(DESTDIR)$(ETCXENDIR)/bugtool/xcp-rrdd-plugins/stuff.xml
 	install -D -m 755 ocaml/xcp-rrdd/bin/rrdp-scripts/sysconfig-rrdd-plugins $(DESTDIR)/etc/sysconfig/xcp-rrdd-plugins

ocaml/xcp-rrdd/bin/rrdp-dcmi/dune

@@ -0,0 +1,16 @@
+(executable
+  (modes exe)
+  (name rrdp_dcmi)
+  (package rrdd-plugins)
+  (public_name xcp-rrdd-dcmi)
+  (libraries
+    dune-build-info
+    rrdd-plugin
+    rrdd-plugins.libs
+    xapi-idl.rrd
+    xapi-log
+    xapi-rrd
+    astring
+  )
+)
+

ocaml/xcp-rrdd/bin/rrdp-dcmi/rrdp_dcmi.ml

@@ -0,0 +1,80 @@
+(*
+ * Copyright (c) 2024 Cloud Software Group, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation; version 2.1 only. with the special
+ * exception on linking described in file LICENSE.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *)
+
+(** Read power measurements from IPMI DCMI where available.
+    There is also IPMI SDR entity 21 that returns the same information (power consumption in watts),
+    but isn't always available, and seems to be slower to read, especially when missing.
+ *)
+
+open Rrdd_plugin
+
+module Process = Process (struct let name = "xcp-rrdd-dcmi" end)
+
+open Process
+
+let ipmitool_bin = "/usr/bin/ipmitool"
+
+let ipmitool args =
+  (* we connect to the local /dev/ipmi0 if available to read measurements from local BMC *)
+  ipmitool_bin :: "-I" :: "open" :: args |> String.concat " "
+
+let discover () =
+  Utils.exec_cmd
+    (module Process.D)
+    ~cmdstring:(ipmitool ["dcmi"; "discover"])
+    ~f:(fun line ->
+      (* this code runs once on startup, logging all the output here will be useful for debugging *)
+      D.debug "DCMI discover: %s" line ;
+      if String.trim line = "Power management available" then
+        Some ()
+      else
+        None
+    )
+
+let get_dcmi_power_reading () =
+  Utils.exec_cmd
+    (module Process.D)
+    ~cmdstring:(ipmitool ["dcmi"; "power"; "reading"])
+    ~f:(fun line ->
+      (* example line: '     Instantaneous power reading:                    34 Watts' *)
+      try
+        Scanf.sscanf line " Instantaneous power reading : %f Watts" Option.some
+      with Scanf.Scan_failure _ | End_of_file -> None
+    )
+
+let gen_dcmi_power_reading value =
+  ( Rrd.Host
+  , Ds.ds_make ~name:"DCMI-power-reading"
+      ~description:"Host power usage reported by IPMI DCMI"
+      ~value:(Rrd.VT_Float value) ~ty:Rrd.Gauge ~default:true ~units:"W"
+      ~min:Float.min_float ~max:65534. ()
+  )
+
+let generate_dss () =
+  match get_dcmi_power_reading () with
+  | watts :: _ ->
+      [gen_dcmi_power_reading watts]
+  | _ ->
+      []
+
+let _ =
+  initialise () ;
+  match discover () with
+  | [] ->
+      D.info "IPMI DCMI power reading is unavailable" ;
+      exit 1
+  | _ ->
+      D.info "IPMI DCMI power reading is available" ;
+      main_loop ~neg_shift:0.5 ~target:(Reporter.Local 1)
+        ~protocol:Rrd_interface.V2 ~dss_f:generate_dss

ocaml/xcp-rrdd/bin/rrdp-scripts/sysconfig-rrdd-plugins

@@ -1 +1 @@
-PLUGINS="xcp-rrdd-iostat xcp-rrdd-squeezed xcp-rrdd-xenpm"
+PLUGINS="xcp-rrdd-iostat xcp-rrdd-squeezed xcp-rrdd-xenpm xcp-rrdd-dcmi"