[Xen-devel] [PATCH 2/3] oxenstored: enable logging via syslog, if specified in the config file.

[David Scott <dave.scott@xxxxxxxxxxxxx>]

To log to files the config file should contain:
   xenstored-log-file = /var/log/xenstored.log
   access-log-file = /var/log/xenstored-access.log

(These two files are still the built-in defaults. The log format is
unchanged.)

To log to syslog the config file should contain:
   xenstored-log-file = syslog:<facility>
   access-log-file = syslog:<facility>

where <facility> is the syslog facility to use (e.g. 'daemon' 'local2')

Signed-off-by: David Scott <dave.scott@xxxxxxxxxxxxx>
---
 tools/ocaml/xenstored/logging.ml   | 124 +++++++++++++++++++++++++++----------
 tools/ocaml/xenstored/xenstored.ml |   4 +-
 2 files changed, 94 insertions(+), 34 deletions(-)

diff --git a/tools/ocaml/xenstored/logging.ml b/tools/ocaml/xenstored/logging.ml
index bc3a2ea..e26f804 100644
--- a/tools/ocaml/xenstored/logging.ml
+++ b/tools/ocaml/xenstored/logging.ml
@@ -20,11 +20,42 @@ open Printf
 
 (* Logger common *)
 
+type log_destination =
+       | File of string
+       | Syslog of Syslog.facility
+
+let log_destination_of_string s =
+       let prefix = "syslog:" in
+       let len_prefix = String.length prefix in
+       let len = String.length s in
+       if String.startswith prefix s
+       then Syslog(Syslog.facility_of_string (String.sub s len_prefix (len - 
len_prefix)))
+       else File s
+
+(* The prefix of a log line depends on the log destination *)
+let prefix log_destination ?level ?key date = match log_destination with
+       | File _ ->
+               let level = match level with
+                       | Some x -> Printf.sprintf "|%5s" x
+                       | None -> "" in
+               let key = match key with
+                       | Some x -> "|" ^ x
+                       | None -> "" in
+               Printf.sprintf "[%s%s%s] " date level key
+       | Syslog _ ->
+               let key = match key with
+                       | Some x -> "[" ^ x ^ "] "
+                       | None -> "" in
+               (* Syslog handles the date and level internally *)
+               key
+
+type level = Debug | Info | Warn | Error | Null
+
 type logger =
                { stop: unit -> unit;
                  restart: unit -> unit;
                  rotate: unit -> unit;
-                 write: 'a. ('a, unit, string, unit) format4 -> 'a }
+                 write: ?level:level -> string -> unit }
 
 let truncate_line nb_chars line = 
        if String.length line > nb_chars - 1 then
@@ -54,7 +85,7 @@ let log_rotate ref_ch log_file log_nb_files =
        close_out !ref_ch;
        ref_ch := open_out log_file
 
-let make_logger log_file log_nb_files log_nb_lines log_nb_chars post_rotate =
+let make_file_logger log_file log_nb_files log_nb_lines log_nb_chars 
post_rotate =
        let channel = ref (open_out_gen [Open_append; Open_creat] 0o644 
log_file) in
        let counter = ref 0 in
        let stop() =
@@ -67,22 +98,17 @@ let make_logger log_file log_nb_files log_nb_lines 
log_nb_chars post_rotate =
                log_rotate channel log_file log_nb_files;
                (post_rotate (): unit);
                counter := 0 in
-       let output s =
+       let write ?level s =
                let s = if log_nb_chars > 0 then truncate_line log_nb_chars s 
else s in
                let s = s ^ "\n" in
                output_string !channel s;
                flush !channel;
                incr counter;
                if !counter > log_nb_lines then rotate() in
-       { stop=stop; restart=restart; rotate=rotate; write = fun fmt -> 
Printf.ksprintf output fmt }
-
-
-(* Xenstored logger *) 
+       { stop=stop; restart=restart; rotate=rotate; write=write }
 
 exception Unknown_level of string
 
-type level = Debug | Info | Warn | Error | Null
-
 let int_of_level = function
        | Debug -> 0 | Info -> 1 | Warn -> 2
        | Error -> 3 | Null -> max_int
@@ -104,30 +130,56 @@ let string_of_date () =
                tm.Unix.tm_hour tm.Unix.tm_min tm.Unix.tm_sec
                (int_of_float (1000.0 *. msec))
 
-let xenstored_log_file = ref "/var/log/xenstored.log"
+let make_syslog_logger facility =
+       (* We defer to syslog for log management *)
+       let nothing () = () in
+       let write ?level s =
+               let level = match level with
+                       | Some Error -> Syslog.Err
+                       | Some Warn -> Syslog.Warning
+                       | Some Info -> Syslog.Info
+                       | Some Debug -> Syslog.Debug
+                       | Some Null -> Syslog.Debug
+                       | None -> Syslog.Debug in
+               (* Syslog handles the date and level internally *)
+               Syslog.log facility level s in
+       { stop = nothing; restart = nothing; rotate = nothing; write=write }
+
+let xenstored_log_destination = ref (File "/var/log/xenstored.log")
 let xenstored_log_level = ref Warn
 let xenstored_log_nb_files = ref 10
 let xenstored_log_nb_lines = ref 13215
 let xenstored_log_nb_chars = ref (-1)
 let xenstored_logger = ref (None: logger option)
 
-let init_xenstored_log () =
-       if !xenstored_log_level <> Null && !xenstored_log_nb_files > 0 then
-               let logger =
-                       make_logger 
-                               !xenstored_log_file !xenstored_log_nb_files 
!xenstored_log_nb_lines
-                               !xenstored_log_nb_chars ignore in
-               let date = string_of_date() in
-               logger.write ("[%s|%5s|%s] Xen Storage Daemon, version %d.%d") 
date "" "startup"
-                 Define.xenstored_major Define.xenstored_minor;
-               xenstored_logger := Some logger
+let set_xenstored_log_destination s =
+       xenstored_log_destination := log_destination_of_string s
+
+let set_xenstored_logger logger =
+       xenstored_logger := Some logger;
+       logger.write ~level:Info (Printf.sprintf "Xen Storage Daemon, version 
%d.%d"
+       Define.xenstored_major Define.xenstored_minor)
+
+
+let init_xenstored_log () = match !xenstored_log_destination with
+       | File file ->
+               if !xenstored_log_level <> Null && !xenstored_log_nb_files > 0 
then
+                       let logger =
+                               make_file_logger 
+                                       file !xenstored_log_nb_files 
!xenstored_log_nb_lines
+                                       !xenstored_log_nb_chars ignore in
+                       set_xenstored_logger logger
+       | Syslog facility ->
+               set_xenstored_logger (make_syslog_logger facility)
+
 
 let xenstored_logging level key (fmt: (_,_,_,_) format4) =
        match !xenstored_logger with
        | Some logger when int_of_level level >= int_of_level 
!xenstored_log_level ->
                        let date = string_of_date() in
-                       let level = string_of_level level in
-                       logger.write ("[%s|%5s|%s] " ^^ fmt) date level key
+                       let level' = string_of_level level in
+                       let prefix = prefix !xenstored_log_destination 
~level:level' ~key date in
+                       Printf.ksprintf (fun s -> logger.write ~level (prefix ^ 
s)) fmt
        | _ -> Printf.ksprintf ignore fmt
 
 let debug key = xenstored_logging Debug key
@@ -200,7 +252,7 @@ let sanitize_data data =
        String.escaped data
 
 let activate_access_log = ref true
-let access_log_file = ref "/var/log/xenstored-access.log"
+let access_log_destination = ref (File "/var/log/xenstored-access.log")
 let access_log_nb_files = ref 20
 let access_log_nb_lines = ref 13215
 let access_log_nb_chars = ref 180
@@ -209,14 +261,20 @@ let access_log_transaction_ops = ref false
 let access_log_special_ops = ref false
 let access_logger = ref None
 
-let init_access_log post_rotate =
-       if !access_log_nb_files > 0 then
-               let logger =
-                       make_logger
-                               !access_log_file !access_log_nb_files 
!access_log_nb_lines
-                               !access_log_nb_chars post_rotate in
-               access_logger := Some logger
- 
+let set_access_log_destination s =
+       access_log_destination := log_destination_of_string s
+
+let init_access_log post_rotate = match !access_log_destination with
+       | File file ->
+               if !access_log_nb_files > 0 then
+                       let logger =
+                               make_file_logger
+                                       file !access_log_nb_files 
!access_log_nb_lines
+                                       !access_log_nb_chars post_rotate in
+                       access_logger := Some logger
+       | Syslog facility ->
+               access_logger := Some (make_syslog_logger facility)
+
 let access_logging ~con ~tid ?(data="") access_type =
         try
                maybe
@@ -225,7 +283,9 @@ let access_logging ~con ~tid ?(data="") access_type =
                                let tid = string_of_tid ~con tid in
                                let access_type = string_of_access_type 
access_type in
                                let data = sanitize_data data in
-                               logger.write "[%s] %s %s %s" date tid 
access_type data)
+                               let prefix = prefix !access_log_destination 
date in
+                               let msg = Printf.sprintf "%s %s %s %s" prefix 
tid access_type data in
+                               logger.write msg)
                        !access_logger
        with _ -> ()
 
diff --git a/tools/ocaml/xenstored/xenstored.ml 
b/tools/ocaml/xenstored/xenstored.ml
index 64cc106..3416666 100644
--- a/tools/ocaml/xenstored/xenstored.ml
+++ b/tools/ocaml/xenstored/xenstored.ml
@@ -87,13 +87,13 @@ let parse_config filename =
                ("quota-maxsize", Config.Set_int Quota.maxsize);
                ("test-eagain", Config.Set_bool Transaction.test_eagain);
                ("persistent", Config.Set_bool Disk.enable);
-               ("xenstored-log-file", Config.Set_string 
Logging.xenstored_log_file);
+               ("xenstored-log-file", Config.String 
Logging.set_xenstored_log_destination);
                ("xenstored-log-level", Config.String
                        (fun s -> Logging.xenstored_log_level := 
Logging.level_of_string s));
                ("xenstored-log-nb-files", Config.Set_int 
Logging.xenstored_log_nb_files);
                ("xenstored-log-nb-lines", Config.Set_int 
Logging.xenstored_log_nb_lines);
                ("xenstored-log-nb-chars", Config.Set_int 
Logging.xenstored_log_nb_chars);
-               ("access-log-file", Config.Set_string Logging.access_log_file);
+               ("access-log-file", Config.String 
Logging.set_access_log_destination);
                ("access-log-nb-files", Config.Set_int 
Logging.access_log_nb_files);
                ("access-log-nb-lines", Config.Set_int 
Logging.access_log_nb_lines);
                ("access-log-nb-chars", Config.Set_int 
Logging.access_log_nb_chars);
-- 
1.8.1.2


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