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Re: [Libguestfs] [PATCH] Add command trace functionality



On 09/09/09 17:49, Richard W.M. Jones wrote:
From 759de3f6289967a3c9978b4e947a38a4585f404c Mon Sep 17 00:00:00 2001
From: Richard Jones<rjones trick home annexia org>
Date: Wed, 9 Sep 2009 17:48:30 +0100
Subject: [PATCH] Add command trace functionality.

Enable this by calling guestfs_trace (handle, 1) or by
setting the LIBGUESTFS_TRACE=1 environment variable.
---
  guestfish.pod    |    4 +++
  guestfs.pod      |    5 +++
  src/generator.ml |   74 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
  src/guestfs.c    |   17 ++++++++++++
  4 files changed, 100 insertions(+), 0 deletions(-)

diff --git a/guestfish.pod b/guestfish.pod
index 5427b23..3afc967 100644
--- a/guestfish.pod
+++ b/guestfish.pod
@@ -575,6 +575,10 @@ Set the default qemu binary that libguestfs uses.  If not set, then
  the qemu which was found at compile time by the configure script is
  used.

+=item LIBGUESTFS_TRACE
+
+Set C<LIBGUESTFS_TRACE=1>  to enable command traces.
+
  =item PAGER

  The C<more>  command uses C<$PAGER>  as the pager.  If not
diff --git a/guestfs.pod b/guestfs.pod
index d8e4da3..b8379d0 100644
--- a/guestfs.pod
+++ b/guestfs.pod
@@ -983,6 +983,11 @@ used.

  See also L</QEMU WRAPPERS>  above.

+=item LIBGUESTFS_TRACE
+
+Set C<LIBGUESTFS_TRACE=1>  to enable command traces.  This
+has the same effect as calling C<guestfs_set_trace (handle, 1)>.
+
  =item TMPDIR

  Location of temporary directory, defaults to C</tmp>.
diff --git a/src/generator.ml b/src/generator.ml
index 765cb16..6184890 100755
--- a/src/generator.ml
+++ b/src/generator.ml
@@ -805,6 +805,32 @@ is passed to the appliance at boot time.  See C<guestfs_set_selinux>.
  For more information on the architecture of libguestfs,
  see L<guestfs(3)>.");

+  ("set_trace", (RErr, [Bool "trace"]), -1, [FishAlias "trace"],
+   [InitNone, Always, TestOutputTrue (
+      [["set_trace"; "true"];
+       ["get_trace"]])],
+   "enable or disable command traces",
+   "\
+If the command trace flag is set to 1, then commands are
+printed on stdout before they are executed in a format
+which is very similar to the one used by guestfish.  In
+other words, you can run a program with this enabled, and
+you will get out a script which you can feed to guestfish
+to perform the same set of actions.
+
+If you want to trace C API calls into libguestfs (and
+other libraries) then possibly a better way is to use
+the external ltrace(1) command.
+
+Command traces are disabled unless the environment variable
+C<LIBGUESTFS_TRACE>  is defined and set to C<1>.");
+
+  ("get_trace", (RBool "trace", []), -1, [],
+   [],
+   "get command trace enabled flag",
+   "\
+Return the command trace flag.");
+
  ]

  (* daemon_functions are any functions which cause some action
@@ -4630,6 +4656,52 @@ check_state (guestfs_h *g, const char *caller)

  ";

+  (* Generate code to generate guestfish call traces. *)
+  let trace_call shortname style =
+    pr "  if (guestfs__get_trace (g)) {\n";
+
+    let needs_i =
+      List.exists (function
+		   | StringList _ | DeviceList _ ->  true
+		   | _ ->  false) (snd style) in
+    if needs_i then (
+      pr "    int i;\n";
+      pr "\n"
+    );
+
+    pr "    printf (\"%%s\", \"%s\");\n" shortname;
+    List.iter (
+      function
+      | String n			(* strings *)
+      | Device n
+      | Pathname n
+      | Dev_or_Path n
+      | FileIn n
+      | FileOut n ->
+	  (* guestfish doesn't support string escaping, so neither do we *)
+	  pr "    printf (\" \\\"%%s\\\"\", %s);\n" n
+      | OptString n ->			(* string option *)
+	  pr "    if (%s) printf (\" \\\"%%s\\\"\", %s);\n" n n;
+	  pr "    else printf (\" null\");\n"
+      | StringList n
+      | DeviceList n ->			(* string list *)
+	  pr "    printf (\"\\\"\");\n";

There's a missing leading space in the above line.

+	  pr "    for (i = 0; %s[i]; ++i) {\n" n;
+	  pr "      if (i>  0) putchar (' ');\n";
+	  pr "      printf (\"%%s\", %s[i]);\n" n;
+	  pr "    }\n";
+	  pr "    printf (\"\\\"\");\n";

As discussed on the list, this results in commands which can't be executed in guestfish because argument groupings are lost when arguments contain spaces. While this is a limitation of guestfish rather than this patch, a fix in guestfish will require a modification to this patch. Can we hold off on this until guestfish is fixed?

+      | Bool n ->			(* boolean *)
+	  pr "    if (%s) printf (\" true\");\n" n;
+	  pr "    else printf (\" false\");\n"
+      | Int n ->			(* int *)
+	  pr "    printf (\" %%d\", %s);\n" n
+    ) (snd style);
+    pr "    printf (\"\\n\");\n";
+    pr "  }\n";
+    pr "\n";
+  in
+
    (* For non-daemon functions, generate a wrapper around each function. *)
    List.iter (
      fun (shortname, style, _, _, _, _, _) ->
@@ -4638,6 +4710,7 @@ check_state (guestfs_h *g, const char *caller)
        generate_prototype ~extern:false ~semicolon:false ~newline:true
          ~handle:"g" name style;
        pr "{\n";
+      trace_call shortname style;
        pr "  return guestfs__%s " shortname;
        generate_c_call_args ~handle:"g" style;
        pr ";\n";
@@ -4745,6 +4818,7 @@ check_state (guestfs_h *g, const char *caller)
        pr "  guestfs_main_loop *ml = guestfs_get_main_loop (g);\n";
        pr "  int serial;\n";
        pr "\n";
+      trace_call shortname style;
        pr "  if (check_state (g, \"%s\") == -1) return %s;\n" name error_code;
        pr "  guestfs_set_busy (g);\n";
        pr "\n";
diff --git a/src/guestfs.c b/src/guestfs.c
index 571205f..98d99b8 100644
--- a/src/guestfs.c
+++ b/src/guestfs.c
@@ -170,6 +170,7 @@ struct guestfs_h
    int cmdline_size;

    int verbose;
+  int trace;
    int autosync;

    char *path;			/* Path to kernel, initrd. */
@@ -238,6 +239,9 @@ guestfs_create (void)
    str = getenv ("LIBGUESTFS_DEBUG");
    g->verbose = str != NULL&&  strcmp (str, "1") == 0;

+  str = getenv ("LIBGUESTFS_TRACE");
+  g->trace = str != NULL&&  strcmp (str, "1") == 0;
+
    str = getenv ("LIBGUESTFS_PATH");
    g->path = str != NULL ? strdup (str) : strdup (GUESTFS_DEFAULT_PATH);
    if (!g->path) goto error;
@@ -734,6 +738,19 @@ guestfs__version (guestfs_h *g)
    return r;
  }

+int
+guestfs__set_trace (guestfs_h *g, int t)
+{
+  g->trace = !!t;
+  return 0;
+}
+
+int
+guestfs__get_trace (guestfs_h *g)
+{
+  return g->trace;
+}
+
  /* Add a string to the current command line. */
  static void
  incr_cmdline_size (guestfs_h *g)
-- 1.6.2.5

I really like this. It *almost* works in practise. I've found 2 limitations:

String list splitting doesn't work in guestfish. See note above and expect a patch.

It spits out internal state changes. Look at this output:
add_drive "/var/lib/virt-snapshot/images/RHEL39FV32-hda-1252577522.qcow2"
config "-drive" "file=/var/lib/virt-snapshot/images/RHEL39FV32-hda-1252577522.qcow2,cache=off,if=ide"
add_cdrom "/tmp/4BQ6oiKKAJ.iso"
config "-cdrom" "/tmp/4BQ6oiKKAJ.iso"
set_selinux true
launch
wait_ready
list_partitions
is_ready
set_busy
end_busy
pvs
is_ready
set_busy
end_busy
lvs
is_ready
set_busy
end_busy
file "/dev/sda1"
is_ready

We also discussed this on the list. I don't think this is a problem with this patch as such, but that state transition functions are part of the external API. These need to be removed from *all* bindings, including guestfish.

Matt
--
Matthew Booth, RHCA, RHCSS
Red Hat Engineering, Virtualisation Team

M:       +44 (0)7977 267231
GPG ID:  D33C3490
GPG FPR: 3733 612D 2D05 5458 8A8A 1600 3441 EA19 D33C 3490


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