Implement progress messages in the daemon and library.

This implements progress notification messages in the daemon, and
adds a callback in the library to handle them.

No calls are changed so far, so in fact no progress messages can
be generated by this commit.

For more details, see:
https://www.redhat.com/archives/libguestfs/2010-July/msg00003.html
https://www.redhat.com/archives/libguestfs/2010-July/msg00024.html

daemon/daemon.h

@@ -21,6 +21,7 @@
 
 #include <stdio.h>
 #include <stdarg.h>
+#include <stdint.h>
 #include <errno.h>
 #include <unistd.h>
 
@@ -161,6 +162,12 @@ extern int send_file_end (int cancel);
 /* only call this if there is a FileOut parameter */
 extern void reply (xdrproc_t xdrp, char *ret);
 
+/* Notify progress to caller.  This function is self-rate-limiting so
+ * you can call it as often as necessary.  Actions which call this
+ * should add 'Progress' note in generator.
+ */
+extern void notify_progress (uint64_t position, uint64_t total);
+
 /* Helper for functions that need a root filesystem mounted.
  * NB. Cannot be used for FileIn functions.
  */

daemon/proto.c

@@ -26,6 +26,7 @@
 #include <errno.h>
 #include <sys/param.h>		/* defines MIN */
 #include <sys/select.h>
+#include <sys/time.h>
 #include <rpc/types.h>
 #include <rpc/xdr.h>
 
@@ -43,6 +44,15 @@
 int proc_nr;
 int serial;
 
+/* Time at which we received the current request. */
+static struct timeval start_t;
+
+/* Time at which the last progress notification was sent. */
+static struct timeval last_progress_t;
+
+/* Counts the number of progress notifications sent during this call. */
+static int count_progress;
+
 /* The daemon communications socket. */
 static int sock;
 
@@ -54,8 +64,6 @@ main_loop (int _sock)
   char lenbuf[4];
   uint32_t len;
   struct guestfs_message_header hdr;
-  struct timeval start_t, end_t;
-  int64_t start_us, end_us, elapsed_us;
 
   sock = _sock;
 
@@ -112,9 +120,9 @@ main_loop (int _sock)
     }
 #endif
 
-    /* In verbose mode, display the time taken to run each command. */
-    if (verbose)
-      gettimeofday (&start_t, NULL);
+    gettimeofday (&start_t, NULL);
+    last_progress_t = start_t;
+    count_progress = 0;
 
     /* Decode the message header. */
     xdrmem_create (&xdr, buf, len, XDR_DECODE);
@@ -160,11 +168,14 @@ main_loop (int _sock)
 
     /* In verbose mode, display the time taken to run each command. */
     if (verbose) {
+      struct timeval end_t;
       gettimeofday (&end_t, NULL);
 
+      int64_t start_us, end_us, elapsed_us;
       start_us = (int64_t) start_t.tv_sec * 1000000 + start_t.tv_usec;
       end_us = (int64_t) end_t.tv_sec * 1000000 + end_t.tv_usec;
       elapsed_us = end_us - start_us;
+
       fprintf (stderr, "proc %d (%s) took %d.%02d seconds\n",
                proc_nr,
                proc_nr >= 0 && proc_nr < GUESTFS_PROC_NR_PROCS
@@ -533,3 +544,78 @@ send_chunk (const guestfs_chunk *chunk)
 
   return err;
 }
+
+/* Initial delay before sending notification messages, and
+ * the period at which we send them thereafter.  These times
+ * are in microseconds.
+ */
+#define NOTIFICATION_INITIAL_DELAY 2000000
+#define NOTIFICATION_PERIOD         333333
+
+void
+notify_progress (uint64_t position, uint64_t total)
+{
+  struct timeval now_t;
+  gettimeofday (&now_t, NULL);
+
+  /* Always send a notification at 100%.  This simplifies callers by
+   * allowing them to 'finish' the progress bar at 100% without
+   * needing special code.
+   */
+  if (count_progress > 0 && position == total)
+    goto send;
+
+  /* Calculate time in microseconds since the last progress message
+   * was sent out (or since the start of the call).
+   */
+  int64_t last_us, now_us, elapsed_us;
+  last_us =
+    (int64_t) last_progress_t.tv_sec * 1000000 + last_progress_t.tv_usec;
+  now_us = (int64_t) now_t.tv_sec * 1000000 + now_t.tv_usec;
+  elapsed_us = now_us - last_us;
+
+  /* Rate limit. */
+  if ((count_progress == 0 && elapsed_us < NOTIFICATION_INITIAL_DELAY) ||
+      (count_progress > 0 && elapsed_us < NOTIFICATION_PERIOD))
+    return;
+
+ send:
+  /* We're going to send a message now ... */
+  count_progress++;
+  last_progress_t = now_t;
+
+  /* Send the header word. */
+  XDR xdr;
+  char buf[128];
+  uint32_t i = GUESTFS_PROGRESS_FLAG;
+  size_t len;
+  xdrmem_create (&xdr, buf, 4, XDR_ENCODE);
+  xdr_u_int (&xdr, &i);
+  xdr_destroy (&xdr);
+
+  if (xwrite (sock, buf, 4) == -1) {
+    fprintf (stderr, "xwrite failed\n");
+    exit (EXIT_FAILURE);
+  }
+
+  guestfs_progress message = {
+    .proc = proc_nr,
+    .serial = serial,
+    .position = position,
+    .total = total,
+  };
+
+  xdrmem_create (&xdr, buf, sizeof buf, XDR_ENCODE);
+  if (!xdr_guestfs_progress (&xdr, &message)) {
+    fprintf (stderr, "xdr_guestfs_progress: failed to encode message\n");
+    xdr_destroy (&xdr);
+    return;
+  }
+  len = xdr_getpos (&xdr);
+  xdr_destroy (&xdr);
+
+  if (xwrite (sock, buf, len) == -1) {
+    fprintf (stderr, "xwrite failed\n");
+    exit (EXIT_FAILURE);
+  }
+}

src/generator.ml

@@ -6327,11 +6327,12 @@ and generate_xdr () =
  */
 
 const GUESTFS_PROGRAM = 0x2000F5F5;
-const GUESTFS_PROTOCOL_VERSION = 1;
+const GUESTFS_PROTOCOL_VERSION = 2;
 
 /* These constants must be larger than any possible message length. */
 const GUESTFS_LAUNCH_FLAG = 0xf5f55ff5;
 const GUESTFS_CANCEL_FLAG = 0xffffeeee;
+const GUESTFS_PROGRESS_FLAG = 0xffff5555;
 
 enum guestfs_message_direction {
   GUESTFS_DIRECTION_CALL = 0,        /* client -> daemon */
@@ -6370,6 +6371,23 @@ struct guestfs_chunk {
   /* data size is 0 bytes if the transfer has finished successfully */
   opaque data<GUESTFS_MAX_CHUNK_SIZE>;
 };
+
+/* Progress notifications.  Daemon self-limits these messages to
+ * at most one per second.  The daemon can send these messages
+ * at any time, and the caller should discard unexpected messages.
+ * 'position' and 'total' have undefined units; however they may
+ * have meaning for some calls.
+ *
+ * NB. guestfs___recv_from_daemon assumes the XDR-encoded
+ * structure is 24 bytes long.
+ */
+struct guestfs_progress {
+  guestfs_procedure proc;            /* @0:  GUESTFS_PROC_x */
+  unsigned serial;                   /* @4:  message serial number */
+  unsigned hyper position;           /* @8:  0 <= position <= total */
+  unsigned hyper total;              /* @16: total size of operation */
+                                     /* @24: size of structure */
+};
 "
 
 (* Generate the guestfs-structs.h file. *)
@@ -6869,6 +6887,7 @@ and generate_linker_script () =
     "guestfs_set_launch_done_callback";
     "guestfs_set_log_message_callback";
     "guestfs_set_out_of_memory_handler";
+    "guestfs_set_progress_callback";
     "guestfs_set_subprocess_quit_callback";
 
     (* Unofficial parts of the API: the bindings code use these

src/guestfs-internal.h

@@ -122,6 +122,8 @@ struct guestfs_h
   void *                     launch_done_cb_data;
   guestfs_close_cb           close_cb;
   void *                     close_cb_data;
+  guestfs_progress_cb        progress_cb;
+  void *                     progress_cb_data;
 
   int msg_next_serial;
 

src/guestfs.c

@@ -645,3 +645,11 @@ guestfs_set_close_callback (guestfs_h *g,
   g->close_cb = cb;
   g->close_cb_data = opaque;
 }
+
+void
+guestfs_set_progress_callback (guestfs_h *g,
+                               guestfs_progress_cb cb, void *opaque)
+{
+  g->progress_cb = cb;
+  g->progress_cb_data = opaque;
+}

src/guestfs.h

@@ -34,6 +34,8 @@
 extern "C" {
 #endif
 
+#include <stdint.h>
+
 typedef struct guestfs_h guestfs_h;
 
 /*--- Connection management ---*/
@@ -57,14 +59,15 @@ typedef void (*guestfs_log_message_cb) (guestfs_h *g, void *data, char *buf, int
 typedef void (*guestfs_subprocess_quit_cb) (guestfs_h *g, void *data);
 typedef void (*guestfs_launch_done_cb) (guestfs_h *g, void *data);
 typedef void (*guestfs_close_cb) (guestfs_h *g, void *data);
+typedef void (*guestfs_progress_cb) (guestfs_h *g, void *data, int proc_nr, int serial, uint64_t position, uint64_t total);
 
 extern void guestfs_set_log_message_callback (guestfs_h *g, guestfs_log_message_cb cb, void *opaque);
 extern void guestfs_set_subprocess_quit_callback (guestfs_h *g, guestfs_subprocess_quit_cb cb, void *opaque);
 extern void guestfs_set_launch_done_callback (guestfs_h *g, guestfs_launch_done_cb cb, void *opaque);
 extern void guestfs_set_close_callback (guestfs_h *g, guestfs_close_cb cb, void *opaque);
+extern void guestfs_set_progress_callback (guestfs_h *g, guestfs_progress_cb cb, void *opaque);
 
 /*--- Structures and actions ---*/
-#include <stdint.h>
 #include <rpc/types.h>
 #include <rpc/xdr.h>
 #include <guestfs-structs.h>

src/guestfs.pod

@@ -1186,6 +1186,56 @@ languages (eg. if your HLL interpreter has already been cleaned
 up by the time this is called, and if your callback then jumps
 into some HLL function).
 
+=head2 guestfs_set_progress_callback
+
+ typedef void (*guestfs_progress_cb) (guestfs_h *g, void *opaque,
+                                      int proc_nr, int serial,
+                                      uint64_t position, uint64_t total);
+ void guestfs_set_progress_callback (guestfs_h *g,
+                                     guestfs_progress_cb cb,
+                                     void *opaque);
+
+Some long-running operations can generate progress messages.  If
+this callback is registered, then it will be called each time a
+progress message is generated (usually two seconds after the
+operation started, and three times per second thereafter until
+it completes, although the frequency may change in future versions).
+
+The callback receives two numbers: C<position> and C<total>.
+The units of C<total> are not defined, although for some
+operations C<total> may relate in some way to the amount of
+data to be transferred (eg. in bytes or megabytes), and
+C<position> may be the portion which has been transferred.
+
+The only defined and stable parts of the API are:
+
+=over 4
+
+=item *
+
+The callback can display to the user some type of progress bar or
+indicator which shows the ratio of C<position>:C<total>.
+
+=item *
+
+0 E<lt>= C<position> E<lt>= C<total>
+
+=item *
+
+If any progress notification is sent during a call, then a final
+progress notification is always sent when C<position> = C<total>.
+
+This is to simplify caller code, so callers can easily set the
+progress indicator to "100%" at the end of the operation, without
+requiring special code to detect this case.
+
+=back
+
+The callback also receives the procedure number and serial number of
+the call.  These are only useful for debugging protocol issues, and
+the callback can normally ignore them.  The callback may want to
+print these numbers in error messages or debugging messages.
+
 =head1 BLOCK DEVICE NAMING
 
 In the kernel there is now quite a profusion of schemata for naming

src/proto.c

@@ -373,7 +373,15 @@ guestfs___send_to_daemon (guestfs_h *g, const void *v_buf, size_t n)
  *
  * It also checks for EOF (qemu died) and passes that up through the
  * child_cleanup function above.
+ *
+ * Progress notifications are handled transparently by this function.
+ * If the callback exists, it is called.  The caller of this function
+ * will not see GUESTFS_PROGRESS_FLAG.
  */
+
+/* Size of guestfs_progress message on the wire. */
+#define PROGRESS_MESSAGE_SIZE 24
+
 int
 guestfs___recv_from_daemon (guestfs_h *g, uint32_t *size_rtn, void **buf_rtn)
 {
@@ -400,7 +408,13 @@ guestfs___recv_from_daemon (guestfs_h *g, uint32_t *size_rtn, void **buf_rtn)
    */
   ssize_t nr = -4;
 
-  while (nr < (ssize_t) *size_rtn) {
+  for (;;) {
+    ssize_t message_size =
+      *size_rtn != GUESTFS_PROGRESS_FLAG ?
+      *size_rtn : PROGRESS_MESSAGE_SIZE;
+    if (nr >= message_size)
+      break;
+
     rset2 = rset;
     int r = select (max_fd+1, &rset2, NULL, NULL, NULL);
     if (r == -1) {
@@ -450,6 +464,11 @@ guestfs___recv_from_daemon (guestfs_h *g, uint32_t *size_rtn, void **buf_rtn)
         xdr_uint32_t (&xdr, size_rtn);
         xdr_destroy (&xdr);
 
+        /* *size_rtn changed, recalculate message_size */
+        message_size =
+          *size_rtn != GUESTFS_PROGRESS_FLAG ?
+          *size_rtn : PROGRESS_MESSAGE_SIZE;
+
         if (*size_rtn == GUESTFS_LAUNCH_FLAG) {
           if (g->state != LAUNCHING)
             error (g, _("received magic signature from guestfsd, but in state %d"),
@@ -463,6 +482,8 @@ guestfs___recv_from_daemon (guestfs_h *g, uint32_t *size_rtn, void **buf_rtn)
         }
         else if (*size_rtn == GUESTFS_CANCEL_FLAG)
           return 0;
+        else if (*size_rtn == GUESTFS_PROGRESS_FLAG)
+          /*FALLTHROUGH*/;
         /* If this happens, it's pretty bad and we've probably lost
          * synchronization.
          */
@@ -473,11 +494,11 @@ guestfs___recv_from_daemon (guestfs_h *g, uint32_t *size_rtn, void **buf_rtn)
         }
 
         /* Allocate the complete buffer, size now known. */
-        *buf_rtn = safe_malloc (g, *size_rtn);
+        *buf_rtn = safe_malloc (g, message_size);
         /*FALLTHROUGH*/
       }
 
-      size_t sizetoread = *size_rtn - nr;
+      size_t sizetoread = message_size - nr;
       if (sizetoread > BUFSIZ) sizetoread = BUFSIZ;
 
       r = read (g->sock, (char *) (*buf_rtn) + nr, sizetoread);
@@ -524,6 +545,26 @@ guestfs___recv_from_daemon (guestfs_h *g, uint32_t *size_rtn, void **buf_rtn)
   }
 #endif
 
+  if (*size_rtn == GUESTFS_PROGRESS_FLAG) {
+    if (g->state == BUSY && g->progress_cb) {
+      guestfs_progress message;
+      XDR xdr;
+      xdrmem_create (&xdr, *buf_rtn, PROGRESS_MESSAGE_SIZE, XDR_DECODE);
+      xdr_guestfs_progress (&xdr, &message);
+      xdr_destroy (&xdr);
+
+      g->progress_cb (g, g->progress_cb_data,
+                      message.proc, message.serial,
+                      message.position, message.total);
+    }
+
+    free (*buf_rtn);
+    *buf_rtn = NULL;
+
+    /* Process next message. */
+    return guestfs___recv_from_daemon (g, size_rtn, buf_rtn);
+  }
+
   return 0;
 }