parallel: Implemented --hostgroup.

src/parallel

@@ -723,6 +723,7 @@ sub options_hash {
 	 "cat" => \$opt::cat,
 	 "fifo" => \$opt::fifo,
 	 "pipepart|pipe-part" => \$opt::pipepart,
+	 "hostgroup|hostgroups" => \$opt::hostgroups,
 	);
 }
 
@@ -1702,6 +1703,7 @@ sub start_more_jobs {
 	$jobs_started_this_round = 0;
 	# This will start 1 job on each --sshlogin (if possible)
 	# thus distribute the jobs on the --sshlogins round robin
+
 	for my $sshlogin (values %Global::host) {
 	    if($Global::JobQueue->empty() and not $opt::pipe) {
 		# No more jobs in the queue
@@ -2163,14 +2165,33 @@ sub get_job_with_sshlogin {
     # Returns:
     #   next job object for $sshlogin if any available
     my $sshlogin = shift;
+    my $job = undef;
 
-    my $job = $Global::JobQueue->get();
+    if ($opt::hostgroups) {
+	my @other_hostgroup_jobs = ();
+
+        while($job = $Global::JobQueue->get()) {
+	    if($sshlogin->in_hostgroups($job->hostgroups())) {
+		# Found a job for this hostgroup
+		last;
+	    } else {
+		# This job was not in the hostgroups of $sshlogin
+                push @other_hostgroup_jobs, $job;
+            }
+        }
+	$Global::JobQueue->unget(@other_hostgroup_jobs);
+	if(not defined $job) {
+	    # No more jobs
+	    return undef;
+	}
+    } else {
+        $job = $Global::JobQueue->get();
         if(not defined $job) {
             # No more jobs
 	    ::debug("start", "No more jobs: JobQueue empty\n");
             return undef;
         }
-#    if(not $sshlogin->start_more()) { return undef; }
+    }
 
     my $clean_command = $job->replaced();
     if($clean_command =~ /^\s*$/) {
@@ -3335,11 +3356,25 @@ sub new {
     my $class = shift;
     my $sshlogin_string = shift;
     my $ncpus;
-    if($sshlogin_string =~ s:^(\d+)/:: and defined $1) {
+    my %hostgroups;
+    # SSHLogins can have these formats:
+    #   @grp+grp/ncpu//usr/bin/ssh user@server
+    #   ncpu//usr/bin/ssh user@server
+    #   /usr/bin/ssh user@server
+    #   user@server
+    #   ncpu/user@server
+    #   @grp+grp/user@server
+    if($sshlogin_string =~ s:^\@([^/]+)/::) {
+        # Look for SSHLogin hostgroups
+        %hostgroups = map { $_ => 1 } split(/\+/, $1);
+    }
+    if ($sshlogin_string =~ s:^(\d+)/::) {
         # Override default autodetected ncpus unless missing
         $ncpus = $1;
     }
     my $string = $sshlogin_string;
+    # An SSHLogin is always in the hostgroup of its $string-name
+    $hostgroups{$string} = 1;
     my @unget = ();
     my $no_slash_string = $string;
     $no_slash_string =~ s/[^-a-z0-9:]/_/gi;
@@ -3351,6 +3386,7 @@ sub new {
         'max_jobs_running' => undef,
         'orig_max_jobs_running' => undef,
         'ncpus' => $ncpus,
+        'hostgroups' => \%hostgroups,
         'sshcommand' => undef,
         'serverlogin' => undef,
         'control_path_dir' => undef,
@@ -3410,6 +3446,16 @@ sub jobs_completed {
     return $self->{'jobs_completed'};
 }
 
+sub in_hostgroups {
+    # Input:
+    #   @hostgroups = the hostgroups to look for
+    # Returns:
+    #   true if intersection of @hostgroups and the hostgroups of this
+    #        SSHLogin is non-empty
+    my $self = shift;
+    return grep { defined $self->{'hostgroups'}{$_} } @_;
+}
+
 sub inc_jobs_completed {
     my $self = shift;
     $self->{'jobs_completed'}++;
@@ -6136,6 +6182,14 @@ sub tag {
     return $self->{'tag'};
 }
 
+sub hostgroups {
+    my $self = shift;
+    if(not defined $self->{'hostgroups'}) {
+	$self->{'hostgroups'} = $self->{'commandline'}->{'arg_list'}[0][0]->{'hostgroups'};
+    }
+    return @{$self->{'hostgroups'}};
+}
+
 sub exitstatus {
     my $self = shift;
     return $self->{'exitstatus'};
@@ -7391,8 +7445,16 @@ package Arg;
 sub new {
     my $class = shift;
     my $orig = shift;
+    my @hostgroups;
+    if($opt::hostgroups) {
+	if($orig =~ s:@(.+)::) {
+	    # We found hostgroups on the arg
+	    @hostgroups = split(/\+/, $1);
+        }
+    }
     return bless {
 	'orig' => $orig,
+	'hostgroups' => \@hostgroups,
     }, ref($class) || $class;
 }
 

src/parallel.pod

@@ -4188,10 +4188,12 @@ Specifying the name of your distribution is not enough as you may have
 installed software that is not in the VirtualBox images.
 
 If you cannot reproduce the error on any of the VirtualBox images
-above, you should assume the debugging will be done through you. That
-will put more burden on you and it is extra important you give any
-information that help. In general the problem will be fixed faster and
-with less work for you if you can reproduce the error on a VirtualBox.
+above, see if you can build a VirtualBox image on which you can
+reproduce the error. If not you should assume the debugging will be
+done through you. That will put more burden on you and it is extra
+important you give any information that help. In general the problem
+will be fixed faster and with less work for you if you can reproduce
+the error on a VirtualBox.
 
 
 =head1 AUTHOR

src/parallel_tutorial.pod

@@ -1211,7 +1211,7 @@ Output:
 
 Note how job 1 and 2 were tried 3 times, but 0 was not retried because it had exit code 0.
 
-=head2 Limiting the ressources
+=head2 Limiting the resources
 
 To avoid overloading systems GNU Parallel can look at the system load
 before starting another job: