CA-399669: Detect a reason for IPMI readings being unavailable

When the IPMI devices are missing, this is printed in the error line:

$ /usr/bin/ipmitool -I open dcmi discover
Could not open device at /dev/ipmi0 or /dev/ipmi/0 or /dev/ipmidev/0: No such file or directory

Detect this situation so an appropriate warning can be printed.

This needed changes in the function that executes the command, to be able to
process stderr

Example output:
$ ./disco.exe
[debug] Forking command /usr/bin/ipmitool dcmi discover
[debug] Forked command /usr/bin/ipmitool dcmi discover
[ info] DCMI discover: Could not open device at /dev/ipmi0 or /dev/ipmi/0 or /dev/ipmidev/0: No such file or directory
[debug] Process 423018 exited normally with code 1
[ warn] IPMI DCMI power readings not available, stopping. Reason: IPMI devices are missing

Signed-off-by: Pau Ruiz Safont <[email protected]>

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

@@ -2,8 +2,8 @@
   (modes exe)
   (name rrdp_dcmi)
   (libraries
-
     rrdd-plugin
+    rrdd-plugin.base
     rrdd_plugins_libs
     xapi-idl.rrd
     xapi-log

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

@@ -29,29 +29,47 @@ let ipmitool args =
   (* we connect to the local /dev/ipmi0 if available to read measurements from local BMC *)
   ipmitool_bin :: args |> String.concat " "
 
+type discovery_error = Devices_missing
+
+let discovery_error_to_string = function
+  | Devices_missing ->
+      "IPMI devices are missing"
+
 let discover () =
+  let read_out_line line =
+    (* this code runs once on startup, logging all the output here will be useful for debugging *)
+    D.debug "DCMI discover: %s" line ;
+    let line = String.trim line in
+    if String.equal line "Power management available" then
+      Some ()
+    else
+      None
+  in
+  let read_err_line line =
+    (* this code runs once on startup, logging all the output here will be useful for debugging *)
+    D.debug "DCMI discover: %s" line ;
+    let line = String.trim line in
+    if String.starts_with ~prefix:"Could not open device at" line then
+      Some Devices_missing
+    else
+      None
+  in
   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
-    )
+    ~read_out_line ~read_err_line
 
 let get_dcmi_power_reading () =
+  let read_out_line 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
+  in
+  let read_err_line _ = None in
   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
-    )
+    ~read_out_line ~read_err_line
 
 let gen_dcmi_power_reading value =
   ( Rrd.Host
@@ -63,18 +81,23 @@ let gen_dcmi_power_reading value =
 
 let generate_dss () =
   match get_dcmi_power_reading () with
-  | watts :: _ ->
+  | watts :: _, _ ->
       [gen_dcmi_power_reading watts]
   | _ ->
       []
 
 let _ =
   initialise () ;
   match discover () with
-  | [] ->
-      D.warn "IPMI DCMI power readings not available, stopping." ;
-      exit 0
-  | _ ->
+  | () :: _, _ ->
       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
+  | [], errs ->
+      let reason =
+        List.nth_opt errs 0
+        |> Option.map discovery_error_to_string
+        |> Option.value ~default:"unknown"
+      in
+      D.warn "IPMI DCMI power readings not available, stopping. Reason: %s"
+        reason

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

@@ -10,6 +10,7 @@
     mtime
     mtime.clock.os
     rrdd-plugin
+    rrdd-plugin.base
     rrdd_plugin_xenctrl
     rrdd_plugins_libs
     str

ocaml/xcp-rrdd/bin/rrdp-iostat/rrdp_iostat.ml

@@ -124,7 +124,7 @@ module Iostat = struct
 
     (* Keep track of how many results headers we've seen so far *)
     let parsing_section = ref 0 in
-    let process_line str =
+    let read_out_line str =
       let res = Utils.cut str in
       (* Keep values from the second set of outputs *)
       ( if !parsing_section = 2 then
@@ -151,7 +151,10 @@ module Iostat = struct
     (* 2 iterations; 1 second between them *)
 
     (* Iterate through each line and populate dev_values_map *)
-    let _ = Utils.exec_cmd (module Process.D) ~cmdstring ~f:process_line in
+    let read_err_line _ = None in
+    let _ =
+      Utils.exec_cmd (module Process.D) ~cmdstring ~read_out_line ~read_err_line
+    in
 
     (* Now read the values out of dev_values_map for devices for which we have data *)
     List.filter_map
@@ -341,16 +344,19 @@ let exec_tap_ctl_list () : ((string * string) * int) list =
         D.error "Could not find device with physical path %s" phypath ;
         None
   in
-  let process_line str =
+  let read_out_line str =
     try Scanf.sscanf str "pid=%d minor=%d state=%s args=%s@:%s" extract_vdis
     with Scanf.Scan_failure _ | Failure _ | End_of_file ->
       D.warn {|"%s" returned a line that could not be parsed. Ignoring.|}
         tap_ctl ;
       D.warn "Offending line: %s" str ;
       None
   in
-  let pid_and_minor_to_sr_and_vdi =
-    Utils.exec_cmd (module Process.D) ~cmdstring:tap_ctl ~f:process_line
+  let read_err_line _ = None in
+  let pid_and_minor_to_sr_and_vdi, _ =
+    Utils.exec_cmd
+      (module Process.D)
+      ~cmdstring:tap_ctl ~read_out_line ~read_err_line
   in
   let sr_and_vdi_to_minor =
     List.map

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

@@ -2,8 +2,8 @@
   (modes exe)
   (name rrdp_xenpm)
   (libraries
-
     rrdd-plugin
+    rrdd-plugin.base
     rrdd_plugins_libs
     str
     xapi-idl.rrd

ocaml/xcp-rrdd/bin/rrdp-xenpm/rrdp_xenpm.ml

@@ -57,27 +57,30 @@ let gen_pm_cpu_averages cpu_id time =
 
 let get_cpu_averages () : int64 list =
   let pattern = Str.regexp "average cpu frequency:[ \t]+\\([0-9]+\\)[ \t]*$" in
-  let match_fun s =
+  let read_out_line s =
     if Str.string_match pattern s 0 then
       Some (Int64.of_string (Str.matched_group 1 s))
     else
       None
   in
+  let read_err_line _ = None in
   Utils.exec_cmd
     (module Process.D)
     ~cmdstring:(Printf.sprintf "%s %s" xenpm_bin "get-cpufreq-average")
-    ~f:match_fun
+    ~read_out_line ~read_err_line
+  |> fst
 
 let get_states cpu_state : int64 list =
   let pattern =
     Str.regexp "[ \t]*residency[ \t]+\\[[ \t]*\\([0-9]+\\) ms\\][ \t]*"
   in
-  let match_fun s =
+  let read_out_line s =
     if Str.string_match pattern s 0 then
       Some (Int64.of_string (Str.matched_group 1 s))
     else
       None
   in
+  let read_err_line _ = None in
   Utils.exec_cmd
     (module Process.D)
     ~cmdstring:
@@ -89,7 +92,8 @@ let get_states cpu_state : int64 list =
              "get-cpufreq-states"
          )
       )
-    ~f:match_fun
+    ~read_out_line ~read_err_line
+  |> fst
 
 (* list_package [1;2;3;4] 2 = [[1;2];[3;4]] *)
 let list_package (l : 'a list) (n : int) : 'a list list =

ocaml/xcp-rrdd/lib/plugin/rrdd_plugin.mli

@@ -14,31 +14,6 @@
 
 (** Library to simplify writing an rrdd plugin. *)
 
-(** Utility functions useful for rrdd plugins. *)
-module Utils : sig
-  val now : unit -> float
-  (** Return the current unix epoch as an int64. *)
-
-  val cut : string -> string list
-  (** Split a string into a list of strings as separated by spaces and/or
-      	    tabs. *)
-
-  val list_directory_unsafe : string -> string list
-  (** List the contents of a directory, including . and .. *)
-
-  val list_directory_entries_unsafe : string -> string list
-  (** List the contents of a directory, not including . and .. *)
-
-  val exec_cmd :
-       (module Debug.DEBUG)
-    -> cmdstring:string
-    -> f:(string -> 'a option)
-    -> 'a list
-  (** [exec_cmd cmd f] executes [cmd], applies [f] on each of the lines which
-      	    [cmd] outputs on stdout, and returns a list of resulting values for which
-      	    applying [f] returns [Some value]. *)
-end
-
 (** Asynchronous interface to create, cancel and query the state of stats
     reporting threads. *)
 module Reporter : sig

ocaml/xcp-rrdd/lib/plugin/utils.ml

@@ -33,10 +33,13 @@ let list_directory_entries_unsafe dir =
   let dirlist = list_directory_unsafe dir in
   List.filter (fun x -> x <> "." && x <> "..") dirlist
 
-let exec_cmd (module D : Debug.DEBUG) ~cmdstring ~(f : string -> 'a option) =
+let exec_cmd (module D : Debug.DEBUG) ~cmdstring
+    ~(read_out_line : string -> 'a option) ~(read_err_line : string -> 'b option)
+    =
   D.debug "Forking command %s" cmdstring ;
-  (* create pipe for reading from the command's output *)
+  (* create pipes for reading from the command's output *)
   let out_readme, out_writeme = Unix.pipe () in
+  let err_readme, err_writeme = Unix.pipe () in
   let cmd, args =
     match Astring.String.cuts ~empty:false ~sep:" " cmdstring with
     | [] ->
@@ -45,19 +48,25 @@ let exec_cmd (module D : Debug.DEBUG) ~cmdstring ~(f : string -> 'a option) =
         (h, t)
   in
   let pid =
-    Forkhelpers.safe_close_and_exec None (Some out_writeme) None [] cmd args
+    Forkhelpers.safe_close_and_exec None (Some out_writeme) (Some err_writeme)
+      [] cmd args
   in
   Unix.close out_writeme ;
-  let in_channel = Unix.in_channel_of_descr out_readme in
-  let vals = ref [] in
-  let rec loop () =
-    let line = input_line in_channel in
-    let ret = f line in
-    (match ret with None -> () | Some v -> vals := v :: !vals) ;
-    loop ()
+  Unix.close err_writeme ;
+  let read_and_close f fd =
+    let in_channel = Unix.in_channel_of_descr fd in
+    let vals = ref [] in
+    let rec loop () =
+      let line = input_line in_channel in
+      let ret = f line in
+      (match ret with None -> () | Some v -> vals := v :: !vals) ;
+      loop ()
+    in
+    (try loop () with End_of_file -> ()) ;
+    Unix.close fd ; List.rev !vals
   in
-  (try loop () with End_of_file -> ()) ;
-  Unix.close out_readme ;
+  let stdout = read_and_close read_out_line out_readme in
+  let stderr = read_and_close read_err_line err_readme in
   let pid, status = Forkhelpers.waitpid pid in
   ( match status with
   | Unix.WEXITED n ->
@@ -67,4 +76,4 @@ let exec_cmd (module D : Debug.DEBUG) ~cmdstring ~(f : string -> 'a option) =
   | Unix.WSTOPPED s ->
       D.debug "Process %d was stopped by signal %a" pid Debug.Pp.signal s
   ) ;
-  List.rev !vals
+  (stdout, stderr)

ocaml/xcp-rrdd/lib/plugin/utils.mli

@@ -27,7 +27,13 @@ val list_directory_entries_unsafe : string -> string list
 (** List the contents of a directory, not including . and .. *)
 
 val exec_cmd :
-  (module Debug.DEBUG) -> cmdstring:string -> f:(string -> 'a option) -> 'a list
-(** [exec_cmd cmd f] executes [cmd], applies [f] on each of the lines which
-      	    [cmd] outputs on stdout, and returns a list of resulting values for which
-      	    applying [f] returns [Some value]. *)
+     (module Debug.DEBUG)
+  -> cmdstring:string
+  -> read_out_line:(string -> 'a option)
+  -> read_err_line:(string -> 'b option)
+  -> 'a list * 'b list
+(** [exec_cmd cmd out_line err_line] executes [cmd], applies [read_out_line] to
+    each of the lines which [cmd] outputs on stdout, applies [read_err_line] to
+    each of the lines which [cmd] outputs on stderr, and returns a tuple of
+    list with each of the values that the [read_out_line] and [read_err_line]
+    returned [Some value]. *)