Add database log expiry back to housekeeping.

Clean up database log entries with a daily housekeeping task.  For now,
we're keeping 2 weeks worth of log entries, but we also have a max
number of rows allowed (10K/day = 140K rows).  While this sounds like a
lot, it shouldn't have a major impact on database size--probably adding
up to about 25MiB to the DB size (and about 8MiB for indices).

These values may be adjusted in the future, as we get a better feel for
log message representation within these limits.  Also, we may modify the
expiry algorithm to preferentially expire logging from certain
"less-important" applications (i.e. adding a 1wk expiry for
mythcommflag/mythpreviewgen logging or similar).  However, this
implementation is a good start and will prevent unbounded growth of DB
logs.

mythtv/programs/mythbackend/housekeeper.cpp

@@ -188,6 +188,14 @@ void HouseKeeper::RunHouseKeeping(void)
         // These tasks are only done from the master backend
         if (isMaster)
         {
+            // Clean out old database logging entries
+            if (wantToRun("LogClean", 1, 0, 24))
+            {
+                VERBOSE(VB_GENERAL, "Running LogClean");
+                flushDBLogs();
+                updateLastrun("LogClean");
+            }
+
             // Run mythfilldatabase to grab the TV listings
             if (gCoreContext->GetNumSetting("MythFillEnabled", 1))
             {
@@ -291,6 +299,53 @@ void HouseKeeper::RunHouseKeeping(void)
     }
 }
 
+void HouseKeeper::flushDBLogs()
+{
+    int numdays = 14;
+    uint64_t maxrows = 10000 * numdays;  // likely high enough to keep numdays
+
+    QDateTime days = QDateTime::currentDateTime();
+    days = days.addDays(0 - numdays);
+
+    MSqlQuery query(MSqlQuery::InitCon());
+    if (query.isConnected())
+    {
+        QString sql = "DELETE FROM logging WHERE msgtime < :DAYS ;";
+        query.prepare(sql);
+        query.bindValue(":DAYS", days);
+        VERBOSE(VB_GENERAL|VB_EXTRA, QString("Deleting database log entries "
+                                     "from before %1.").arg(days.toString()));
+        if (!query.exec())
+            MythDB::DBError("Delete old log entries", query);
+
+        sql = "SELECT COUNT(0) FROM logging;";
+        query.prepare(sql);
+        if (query.exec())
+        {
+            uint64_t totalrows = 0;
+            while (query.next())
+            {
+                totalrows = query.value(0).toLongLong();
+                VERBOSE(VB_GENERAL|VB_EXTRA, QString("Database has %1 log "
+                                             "entries.").arg(totalrows));
+            }
+            if (totalrows > maxrows)
+            {
+                sql = "DELETE FROM logging ORDER BY msgtime LIMIT :ROWS;";
+                query.prepare(sql);
+                quint64 extrarows = totalrows - maxrows;
+                query.bindValue(":ROWS", extrarows);
+                VERBOSE(VB_GENERAL|VB_EXTRA, QString("Deleting oldest %1 "
+                        "database log entries.").arg(extrarows));
+                if (!query.exec())
+                    MythDB::DBError("Delete excess log entries", query);
+            }
+        }
+        else
+            MythDB::DBError("Query logging table size", query);
+    }
+}
+
 void MFDThread::run(void)
 {
     if (!m_parent)

mythtv/programs/mythbackend/housekeeper.h

@@ -50,6 +50,7 @@ class HouseKeeper
                    bool nowIfPossible = false);
     void updateLastrun(const QString &dbTag);
     QDateTime getLastRun(const QString &dbTag);
+    void flushDBLogs();
     void runFillDatabase();
     void CleanupMyOldRecordings(void);
     void CleanupAllOldInUsePrograms(void);