Improve statistic reporter scheduling.

Use crontab format specification to define the frequency of
statistic report generation.

* src/wydawca.h (stat_report_schedule): New variable.  Replaces
stat_report_interval.
* configure.ac: Check for struct tm.tm_gmtoff.
* src/config.c: New keyword: stat-report-schedule.
* src/micron.c: New file.
* src/micron.h: New file.
* src/Makefile.am: Add new files.
* src/timer.c (wy_thr_stat): Use micron scheduler.
* doc/wydawca.texi: Document stat-report-schedule.
* NEWS: Document stat-report-schedule.

9 files changed, 559 insertions, 59 deletions

diff --git a/NEWS b/NEWS
index ebe721e..2778180 100644
--- a/NEWS
+++ b/NEWS
@@ -1,4 +1,4 @@
-Wydawca NEWS -- history of user-visible changes. 2020-04-27
+Wydawca NEWS -- history of user-visible changes. 2020-04-29
 See the end of file for copying conditions.
 
 Please send Wydawca bug reports to <bug-wydawca@gnu.org.ua>.
@@ -75,7 +75,11 @@ notification connections.  Default is 16.
 This new statement configures the maximum idle timeout of an
 upload notification connection. Default is 10 seconds.
 
-** stat-report-interval statement
+** stat-report-schedule statement
+
+Schedules generation of statistic reports in daemon mode.  The
+argument is a crontab(5) time specification.  The default is
+"@hourly".
 
 ** The "statistics" event.
 
diff --git a/configure.ac b/configure.ac
index 1aed22a..2cffbed 100644
--- a/configure.ac
+++ b/configure.ac
@@ -56,6 +56,11 @@ AC_TYPE_SIZE_T
 AC_HEADER_STDBOOL
 AC_SYS_LARGEFILE
 
+AC_CHECK_MEMBERS([struct tm.tm_gmtoff],,,
+                 [#include <sys/types.h>
+#include <time.h>
+])
+
 # Checks for library functions.
 AC_FUNC_FORK
 AC_FUNC_MALLOC
diff --git a/doc/wydawca.texi b/doc/wydawca.texi
index 349d9ba..ddfcca9 100644
--- a/doc/wydawca.texi
+++ b/doc/wydawca.texi
@@ -2234,11 +2234,36 @@ EOT;
 @node statistics
 @section Statistics
 @cindex statistics
-At the end of the run, @command{wydawca} can print a detailed
-statistics of its execution on the diagnostic channel @samp{info}.
-The statistics is printed only if at least one of its items is not zero.
+Periodically @command{wydawca} produces statistic dumps.  These dumps
+are displayed on the diagnostic channel @samp{info} (and optionally
+mailed to the admimistrator).  The frequency with which they are
+produced is defined by the @code{stat-report-schedule} configuration
+statement.
+
+@deffn {Config} stat-report-schedule time
+Schedules generation of statistic reports.  The @var{time} argument
+is a time specification in @samp{crontab} format
+(@pxref{crontab,,,crontab(5),crontab(5) manual page}).  By default,
+reports are generated hourly.
+
+To create reports each three hours, set
+
+@example
+stat-report-schedule "0 */3 * * *";
+@end example
+
+To create them at midnight, use
+
+@example
+stat-report-schedule "@@midnight";
+@end example
+@end deffn
+
+Statistic report is suppressed if there were no uploads since the last
+report.
+
 The following example illustrates what you might get if you configured
-full statistics output:
+full statistic reports:
 
 @smallexample
 errors: 0
@@ -2256,8 +2281,8 @@ symlinks created: 0
 symlinks removed: 0
 @end smallexample
 
-  Each item in this statistics is configurable, and a
-unique configuration keyword is associated with it. The statistics
+  Each item in this report is configurable, and a
+unique configuration keyword is associated with it. The statistic
 items and their corresponding keywords are described in the table
 below:
 
@@ -2322,12 +2347,12 @@ A symlink is created.
 A symlink is removed.
 @end table
 
-There are two ways to enable the statistics logging.  The
-@dfn{built-in} statistics output is enabled using the
+There are two ways to enable statistic reports.  The
+@dfn{built-in} statistic output is enabled using the
 @code{statistics} keyword.
 
 @deffn {Config} statistics list
-  The amount of information included in the statistics summary is
+  The amount of information included in statistic report is
 configured using the @code{statistics} statement. This statement takes
 a list of arguments, each one being one of the keywords, described
 above. For example, the following statement causes only the
@@ -2354,10 +2379,10 @@ statistics none;
 @end smallexample
 
 @kwindex all@r{, statistics}
-  Another special keyword is @samp{all}. It enables full statistics
-output. This keyword may also be followed by any number of statistics
-keywords, which are in this case @emph{excluded} from the
-summary. For example, to output all statistics, except errors and
+  Another special keyword is @samp{all}. It enables full statistic
+report. This keyword may also be followed by any number of statistic
+item names, which are in this case @emph{excluded} from the
+summary. For example, to output all statistic data, except errors and
 warnings one would set:
 
 @smallexample
@@ -2547,7 +2572,7 @@ detailed description.
 @item statistics
   This event produces statistics about the recent jobs performed
 by @command{wydawca}.  In daemon mode, it is scheduled periodically
-as controlled by @code{stat-report-interval} statement.  In cron mode
+as controlled by the @code{stat-report-schedule} statement.  In cron mode
 it is emitted when all spools have been processed.
 
 For compatibility with @command{wydawca} versions prior to 3.1.95, the
@@ -2603,7 +2628,7 @@ constructed from the name of the user @command{wydawca} runs as
 runs at. 
 
 @deffn {mod_mailutils} admin-address email
-Sets the admin email address or addresses. The statistics
+Sets the admin email address or addresses. The statistic
 notifications and any notifications configured to be sent to admins
 will be forwarded to this address. The @var{email} argument is either
 a @acronym{RFC} 822 email address, or a list of such addresses. For
@@ -2821,8 +2846,8 @@ where @var{name} is the message name as used in @code{define-message}.
 @end deffn
 
 @deffn {mail-statistics} statistics item-list
-The argument is a list of statistics keywords as described in
-@ref{statistics}. A report will be sent only if statistics
+The argument is a list of statistic item names as described in
+@ref{statistics}. A report will be sent only if statistic
 counters for at least one of the requested categories are not
 zero. For example, the following statement requires sending
 notifications only if there occurred any errors or access violation
@@ -2843,9 +2868,9 @@ The statistics message is sent to addresses configured by
 @code{admin-address} statement (@pxref{mod_mailutils, admin-address}).
 
 @cindex variables in admin notifications
-The variables available for use in statistics reports are:
+The variables available for use in statistic reports are:
 
-@anchor{statistics variables}
+@anchor{statistic variables}
 @multitable @columnfractions 0.30 0.70
 @headitem Variable @tab Replaced with
 @kwindex date
@@ -3277,7 +3302,7 @@ This statement is ignored if the @code{message} statement is present.
 
 @deffn {mod_logstat config} message text
 Specifies the message to be logged.  The @var{text} argument can
-contain references to statistics variables (@pxref{statistics
+contain references to statistic variables (@pxref{statistic
 variables}).
 @end deffn
 
@@ -3462,7 +3487,12 @@ umask @var{mask:@i{octal}};
 # @xref{archivation, archive-signatures}.
 archive-signatures @var{arg:@i{boolean}};
 
-# @r{Print these stats at the end of each run.}
+# @r{Schedule generation of statistic reports.}
+# @xref{statistics}.
+stat-report-schedule @var{time:@i{crontab-time}};
+
+# @r{Generate statistic reports if one or more of these items
+# changed.}  
 # @xref{statistics}.
 statistics @var{items:@i{string}};
 
diff --git a/src/Makefile.am b/src/Makefile.am
index 5b70f5e..15238d4 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -44,6 +44,8 @@ wydawca_SOURCES=\
  null.c\
  timer.c\
  thread_name.c\