Add new ovflushcount parameter in inn.conf

The icdsynccount parameter was used for the flushing of both the active
and history files, and buffindexed (though undocumented for that use with
buffindexed).

Add a new parameter for that use.

close #280

doc/pod/buffindexed.conf.pod

@@ -35,6 +35,9 @@ method.
 You can see the current usage of the buffers with the B<-o> option to
 B<inndf>.
 
+The overview data of received articles are flushed to disk every
+I<ovflushcount> articles, as set in F<inn.conf>.
+
 In the F<buffindexed.conf> file, blank lines and lines beginning with a
 number sign (C<#>) are ignored.  All other lines must be of the format:
 

doc/pod/inn.conf.pod

@@ -670,6 +670,18 @@ set to true and the storage method for these newsgroups does not have
 self-expire functionality, storing overview data will fail.
 The default is unset.
 
+=item I<ovflushcount>
+
+How many articles received between flushing their overview data to disk.
+This parameter is only used for the buffindexed overview storage method, and
+defaults to C<50>.  (Flushing to disk is parameterized differently for other
+methods: I<txn_nosync> in F<ovdb.conf>, I<transrowlimit> and I<transtimelimit>
+in F<ovsqlite.conf>, and always after each article arrival for tradindexed.)
+
+See I<icdsynccount> (related to flushes of the I<active> and I<history> files)
+for more information about this trade-off between faster speed and more data
+loss if B<innd> crashes.
+
 =item I<ovmethod>
 
 Which overview storage method to use.  Currently supported values are

doc/pod/news.pod

@@ -35,6 +35,13 @@ NoCeM issuers, and make sure the right PGP keys are present on your system.
 
 =item *
 
+Added a new I<ovflushcount> parameter in F<inn.conf>, defaulting to C<50>, to
+parameterize the number of articles received between flushing their overview
+data to disk, when using the buffindexed overview storage method.  (In
+previous releases, that number was ten times the value of I<icdsynccount>.)
+
+=item *
+
 B<innreport> now supports high-precision timestamps like
 C<2023-07-29T04:15:01.889064+02:00> that syslog can be parameterized to use;
 daily Usenet reports otherwise indicated all these logs as unknown entries,

include/inn/innconf.h

@@ -80,6 +80,7 @@ struct innconf {
     bool mergetogroups;          /* Refile articles from to.* into to */
     bool nfswriter;              /* Use NFS writer functionality */
     unsigned long overcachesize; /* fd size cache for tradindexed */
+    unsigned long ovflushcount;  /* Articles between buffindexed flushes */
     char *ovgrouppat;            /* Newsgroups to store overview for */
     char *ovmethod;              /* Which overview method to use */
     bool storeonxref;            /* SMstore use Xref to detemine class? */

lib/innconf.c

@@ -210,6 +210,7 @@ static const struct config config_table[] = {
     {K(nfswriter),                  BOOL(false)       },
     {K(nnrpdcheckart),              BOOL(true)        },
     {K(overcachesize),              UNUMBER(128)      },
+    {K(ovflushcount),               UNUMBER(50)       },
     {K(ovgrouppat),                 STRING(NULL)      },
     {K(storeonxref),                BOOL(true)        },
     {K(tradindexedmmap),            BOOL(true)        },

samples/inn.conf.in

@@ -70,6 +70,7 @@ groupbaseexpiry:             true
 mergetogroups:               false
 nfswriter:                   false
 overcachesize:               128
+ovflushcount:                50
 #ovgrouppat:
 storeonxref:                 true
 useoverchan:                 false

storage/buffindexed/buffindexed.c

@@ -54,7 +54,7 @@
 ** do file write for each update.  Instead we'll do it at every
 ** OVBUFF_SYNC_COUNT updates.
 */
-#define OVBUFF_SYNC_COUNT   (innconf->icdsynccount * 10 + 1)
+#define OVBUFF_SYNC_COUNT   (innconf->ovflushcount)
 
 /* ovbuff header */
 #define OVBUFFMASIZ         8
@@ -763,6 +763,7 @@ ovbuffinit_disks(void)
             ovbuff->usedblk = 0;
             ovbuff->freeblk = 0;
             ovbuff->updated = 0;
+            /* Force a flush. */
             ovbuff->dirty = OVBUFF_SYNC_COUNT + 1;
             notice("buffindexed: no magic cookie found for ovbuff %d, "
                    "initializing",

tests/overview/api-t.c

@@ -59,8 +59,7 @@ group_del(void *entry)
 
 /* Build a stripped-down innconf struct that contains only those settings that
    the overview backend cares about.  (May still be missing additional bits
-   for ovdb.)
-   innconf->icdsynccount defines OVBUFF_SYNC_COUNT. */
+   for ovdb.) */
 static void
 fake_innconf(void)
 {
@@ -76,10 +75,10 @@ fake_innconf(void)
     memset(innconf, 0, sizeof(*innconf));
     innconf->enableoverview = true;
     innconf->groupbaseexpiry = true;
-    innconf->icdsynccount = 10;
     innconf->keepmmappedthreshold = 1024;
     innconf->nfsreader = false;
     innconf->overcachesize = 20;
+    innconf->ovflushcount = 50;
     innconf->ovgrouppat = NULL;
     innconf->pathdb = xstrdup("ov-tmp");
     innconf->pathetc = xstrdup("etc");

tests/overview/overview-t.c

@@ -87,10 +87,10 @@ fake_innconf(void)
     memset(innconf, 0, sizeof(*innconf));
     innconf->enableoverview = true;
     innconf->groupbaseexpiry = true;
-    innconf->icdsynccount = 10;
     innconf->keepmmappedthreshold = 1024;
     innconf->nfsreader = false;
     innconf->overcachesize = 20;
+    innconf->ovflushcount = 50;
     innconf->ovgrouppat = NULL;
     innconf->ovmethod = xstrdup(STRING(OVTYPE));
     innconf->pathdb = xstrdup("ov-tmp");