* implement automatic log file cleanup, document it

TODO

@@ -2,7 +2,7 @@
 
 * Future release
 
-** release 0.7 [66%]
+** release 0.7 [81%]
 
    - [X] signal handler for indexing
    - [X] fix max 10000 matches limit
@@ -13,7 +13,7 @@
    - [X] fix the batch stuff
    - [ ] mu view <path>
    - [X] basic test suite
-   - [ ] auto clean log file
+   - [X] auto clean log file
    - [X] configure error for missing ->dt_dtype
 
 ** release 0.8 [%]

configure.ac

@@ -27,7 +27,7 @@ AM_INIT_AUTOMAKE([dist-bzip2])
 # versioning, as we hopefully don't have updates for each version;
 # also, this has nothing to do with the version of the Xapian library
 #
-AC_DEFINE(MU_XAPIAN_DB_VERSION,["6.999"], [Schema version of the database])
+AC_DEFINE(MU_XAPIAN_DB_VERSION,["6.9999"], [Schema version of the database])
 
 LT_INIT # don't use AC_PROG_LIBTOOL anymore
 
@@ -66,7 +66,7 @@ AC_STRUCT_DIRENT_D_INO
 
 
 # glib2?
-PKG_CHECK_MODULES(GLIB,glib-2.0)
+PKG_CHECK_MODULES(GLIB, glib-2.0 gio-2.0)
 AC_SUBST(GLIB_CFLAGS)
 AC_SUBST(GLIB_LIBS)
 

man/mu.1

@@ -63,7 +63,8 @@ store and read its database and logs. By default, \fI~/.mu\fR is used.
 makes \fBmu\fR generate extra debug information,
 useful for debugging the program itself. By default, debug information goes to
 the log file, \fI~/.mu/mu.log\fR. It can safely be deleted when \fBmu\fR is
-not running. Note, with the debug option, the log file can grow rather quickly.
+not running. Note, with the debug option, the log file can grow rather
+quickly. See the note on logging below.
 
 .TP
 \fB\-q\fR, \fB\-\-quiet\fR
@@ -485,19 +486,26 @@ If the creation somehow fails, for safety reasons, \fBno\fR attempt is made to
 remove any parts that were created.
 
 .SH FILES
-By default, \fBmu index\fR stores its message database in
-\fI~/.mu/xapian-<version>\fR, where \fI<version>\fR is the version of the
-database layout, which is not necessarily the same as the \fBmu\fR version
-number.
+By default, \fBmu index\fR stores its message database in \fI~/.mu/xapian\fR;
+the database has an embedded version number, and \fBmu\fR will automatically
+update it when it notices a different version. This allows for automatic
+updating of \fBmu\fR-versions, without the need to clear out any old
+databases.
 
-\fBmu\fR stores logs of its operations in \fI~/.mu/mu.log\fR. These can grow
-quite big when using the \fI\-\-debug\fR option, but they can be safely
-delete when \fBmu\fR is not running.
+However, note that versions of \fBmu\fR before 0.7 used a different scheme,
+which put the database in \fI~/.mu/xapian\-<version>\fR. These older databases
+can safely be deleted. Starting from version 0.7, this manual cleanup should
+no longer be needed.
 
-To store various \fBmu\fR-files elsewhere from their default location, one can
-use the \fI\-\-muhome\fR option, as discussed in the \fBGENERAL OPTIONS\fR
-section.
+By default, \fBmu\fR stores logs of its operations and queries in \fI~/.mu/mu.log\fR.
+Upon startup, \fBmu\fR checks the size of this log file. If it exceeds 1 MB,
+it will be moved to \fI~/.mu/mu.log.old\fR, overwriting any existing file of
+that name, and start with an empty \fI~/.mu/mu.log\fR. This scheme allows for
+continued use of \fBmu\fR without the need for any manual maintenance of log
+files.
 
+To store these files elsewhere from their default location, one can use the
+\fI\-\-muhome\fR option, as discussed in the \fBGENERAL OPTIONS\fR section.
 
 .SH ENVIRONMENT
 

src/mu-log.c

@@ -27,6 +27,7 @@
 #include <time.h>
 #include <errno.h>
 #include <string.h>
+#include <gio/gio.h>
 
 #include "mu-log.h"
 #include "mu-util.h"
@@ -113,9 +114,58 @@ mu_log_init_with_fd (int fd, gboolean doclose,
 	return TRUE;
 }
 
+static gboolean
+log_file_backup_maybe (const char *logfile)
+{
+	struct stat statbuf;
+	
+	if (stat (logfile, &statbuf) != 0) {
+		if (errno == ENOENT)
+			return TRUE; /* it did not exist yet, no problem */
+		else {
+			g_warning ("Failed to stat(2) %s", logfile);
+			return FALSE;
+		}
+	}
+
+	/* log file is still below the max size? */
+	if (statbuf.st_size <= MU_MAX_LOG_FILE_SIZE)
+		return TRUE;
+
+	/* log file is too big!; we move it to <logfile>.old, overwriting */
+	{
+		GFile *src, *dst;
+		gchar *tmp;
+		GError *err;
+		gboolean rv;
+		
+		src = g_file_new_for_path (logfile);
+		tmp = g_strdup_printf ("%s.old", logfile);
+		dst = g_file_new_for_path (tmp);
+		g_free (tmp);
+
+		err = NULL;
+		rv = g_file_move (src, dst, G_FILE_COPY_OVERWRITE, NULL, NULL, NULL, &err);
+
+		if (!rv) {
+			g_warning ("Failed to move %s to %s.old: %s", logfile, logfile,
+				   err ? err->message : "?");
+			if (err)
+				g_error_free (err);
+		}
+			
+		g_object_unref (G_OBJECT(src));
+		g_object_unref (G_OBJECT(dst));
+
+		return rv;
+		
+	}
+}
+
+
 gboolean
-mu_log_init  (const char* muhome, gboolean append,
-	      gboolean quiet, gboolean debug)
+mu_log_init  (const char* muhome,
+	      gboolean backup, gboolean quiet, gboolean debug)
 {
 	int fd;
 	gchar *logfile;
@@ -131,8 +181,13 @@ mu_log_init  (const char* muhome, gboolean append,
 	
 	logfile = g_strdup_printf ("%s%c%s", muhome,
 				   G_DIR_SEPARATOR, MU_LOG_FILE);
-	fd = open (logfile,  O_WRONLY|O_CREAT|(append ? O_APPEND : O_TRUNC),
-		   00600);
+
+	if (backup && !log_file_backup_maybe(logfile)) {
+		g_warning ("Failed to backup log file");
+		return FALSE;
+	}
+	
+	fd = open (logfile,  O_WRONLY|O_CREAT|O_APPEND, 00600);
 	if (fd < 0) 
 		g_warning ("%s: open() of '%s' failed: %s\n",  __FUNCTION__,
 			   logfile, strerror(errno));

src/mu-log.h

@@ -26,17 +26,21 @@
 
 G_BEGIN_DECLS
 
+#define MU_MAX_LOG_FILE_SIZE 1000 * 1000 /* 1 MB (SI units) */
+
 /** 
  * write logging information to a log file
  * 
  * @param muhome the mu home directory
- * @param append append to logfile, instead of overwriting
+ * @param backup if TRUE and size of log file > MU_MAX_LOG_FILE_SIZE, move
+ * the log file to <log file>.old and start a new one. The .old file will overwrite
+ * existing files of that name
  * @param quiet don't log non-errors to stdout/stderr
  * @param debug include debug-level information.
  * 
  * @return TRUE if initialization succeeds, FALSE otherwise
  */
-gboolean mu_log_init  (const char* muhome, gboolean append,
+gboolean mu_log_init  (const char* muhome, gboolean backup,
 		       gboolean quiet, gboolean debug);
 
 /**