add code to update the statuses in the Server record every second. This code also reduces the timeout from .1 seconds to 1 second. Should reduce load by zmdc on low power devices. I see no reason to poll that heavily...

scripts/ZoneMinder/lib/ZoneMinder/Database.pm

@@ -157,6 +157,16 @@ sub zmDbGetMonitors {
   return( \@monitors );
 }
 
+sub zmSQLExecute {
+  my $sql = shift;
+  
+  my $sth = $dbh->prepare_cached( $sql )
+    or croak( "Can't prepare '$sql': ".$dbh->errstr() );
+  my $res = $sth->execute( @_ )
+    or croak( "Can't execute '$sql': ".$sth->errstr() );
+  return 1;
+}
+
 sub zmDbGetMonitor {
   zmDbConnect();
 

scripts/zmdc.pl.in

@@ -55,7 +55,7 @@ use bytes;
 # ==========================================================================
 
 # in useconds, not seconds.
-use constant MAX_CONNECT_DELAY => 10*1000*1000;
+use constant MAX_CONNECT_DELAY => 40;
 
 # ==========================================================================
 #
@@ -69,6 +69,8 @@ use POSIX;
 use Socket;
 use IO::Handle;
 use Time::HiRes qw(usleep);
+use Sys::MemInfo qw(totalmem freemem totalswap freeswap);
+
 use autouse 'Pod::Usage'=>qw(pod2usage);
 #use Data::Dumper;
 
@@ -140,12 +142,20 @@ foreach my $arg ( @ARGV ) {
   }
 }
 
+my $dbh = zmDbConnect();
+
 socket( CLIENT, PF_UNIX, SOCK_STREAM, 0 ) or Fatal( "Can't open socket: $!" );
 
 my $saddr = sockaddr_un( SOCK_FILE );
 my $server_up = connect( CLIENT, $saddr );
 if ( ! $server_up ) {
-  # Server is not up.  Some commands can still be handled
+  if ( $Config{ZM_SERVER_ID} ) {
+    if ( ! defined $dbh->do(q{UPDATE Servers SET Status=?,TotalMem=?,FreeMem=?,TotalSwap=?,FreeSwap=? WHERE Id=?}, undef,
+          'NotRunning', &totalmem, &freemem, &totalswap, &freeswap, $Config{ZM_SERVER_ID} ) ) {
+      Error("Failed Updating status of Server record to Not RUnning for Id=$Config{ZM_SERVER_ID}" . $dbh->errstr());
+    }
+  }
+# Server is not up.  Some commands can still be handled
   if ( $command eq 'logrot' ) {
     # If server is not running, then logrotate doesn't need to do anything.
     exit();
@@ -172,7 +182,7 @@ if ( ! $server_up ) {
     my $attempts = 0;
     while( !connect( CLIENT, $saddr ) ) {
       $attempts++;
-      Error("Waiting for zmdc.pl server process, attempt $attempts" );
+      Error("Waiting for zmdc.pl server process at " . SOCK_FILE.", attempt $attempts" );
       Fatal( "Can't connect: $!" ) if ($attempts > MAX_CONNECT_DELAY);
       usleep(200000);
     } # end while
@@ -219,6 +229,7 @@ use POSIX;
 use Socket;
 use IO::Handle;
 use Time::HiRes qw(usleep);
+use Sys::MemInfo qw(totalmem freemem totalswap freeswap);
 #use Data::Dumper;
 
 use constant KILL_DELAY => 100*1000; # 1/10th of a second
@@ -250,11 +261,15 @@ sub run {
 
   killAll( 1 );
 
+  dPrint( ZoneMinder::Logger::INFO, 'Socket should be open at ' .main::SOCK_FILE  );
+  my $dbh = zmDbConnect(1);
+  dPrint( ZoneMinder::Logger::INFO, 'Connected to db' );
   socket( SERVER, PF_UNIX, SOCK_STREAM, 0 ) or Fatal( "Can't open socket: $!" );
-  unlink( main::SOCK_FILE ) or Error( 'Unable to unlink ' . main::SOCK_FILE .". Error message was: $!" ) if ( -e main::SOCK_FILE );
+  unlink( main::SOCK_FILE ) or Error( 'Unable to unlink ' . main::SOCK_FILE .". Error message was: $!" ) if -e main::SOCK_FILE;
   bind( SERVER, $saddr ) or Fatal( "Can't bind to " . main::SOCK_FILE . ": $!" );
   listen( SERVER, SOMAXCONN ) or Fatal( "Can't listen: $!" );
 
+
   $SIG{CHLD} = \&reaper;
   $SIG{INT} = \&shutdownAll;
   $SIG{TERM} = \&shutdownAll;
@@ -265,8 +280,17 @@ sub run {
   vec( $rin, fileno(SERVER), 1 ) = 1;
   my $win = $rin;
   my $ein = $win;
-  my $timeout = 0.1;
+  my $timeout = 1;
   while( 1 ) {
+    if ( $Config{ZM_SERVER_ID} ) {
+      $dbh = zmDbConnect() if ! $dbh->ping();
+      if ( ! defined $dbh->do(q{UPDATE Servers SET Status=?,TotalMem=?,FreeMem=?,TotalSwap=?,FreeSwap=? WHERE Id=?}, undef,
+            'Running', &totalmem, &freemem, &totalswap, &freeswap, $Config{ZM_SERVER_ID} ) ) {
+        Error("Failed Updating status of Server record for Id=$Config{ZM_SERVER_ID}".$dbh->errstr());
+      } else {
+        Debug("Updated status of Server record for Id=$Config{ZM_SERVER_ID}".$dbh->errstr());
+      }
+    }
     my $nfound = select( my $rout = $rin, undef, undef, $timeout );
     if ( $nfound > 0 ) {
       if ( vec( $rout, fileno(SERVER), 1 ) ) {
@@ -327,6 +351,12 @@ sub run {
       .strftime( '%y/%m/%d %H:%M:%S', localtime() )
       ."\n"
       );
+  if ( $Config{ZM_SERVER_ID} ) {
+    $dbh = zmDbConnect() if ! $dbh->ping();
+    if ( ! defined $dbh->do(q{UPDATE Servers SET Status='NotRunning' WHERE Id=?}, undef, $Config{ZM_SERVER_ID} ) ) {
+      Error("Failed Updating status of Server record for Id=$Config{ZM_SERVER_ID}".$dbh->errstr());
+    }
+  }
   unlink( main::SOCK_FILE ) or Error( 'Unable to unlink ' . main::SOCK_FILE .". Error message was: $!" ) if ( -e main::SOCK_FILE );
   unlink( ZM_PID ) or Error( 'Unable to unlink ' . ZM_PID .". Error message was: $!" ) if ( -e ZM_PID );
   exit();
@@ -393,7 +423,7 @@ sub start {
     sigprocmask( SIG_SETMASK, $sigset ) or Fatal( "Can't restore SIGCHLD: $!" );
   } elsif ( defined($cpid ) ) {
 # Force reconnection to the db.
-    zmDbConnect(1);
+    $dbh = zmDbConnect(1);
     logReinit();
 
     dPrint( ZoneMinder::Logger::INFO, "'".join( ' ', ( $daemon, @args ) )