Initial commit

19 files changed, 1347 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..229cce2
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,5 @@
+monitor
+myclient
+myservice
+notifier
+.*.swp
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..b5241f5
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,19 @@
+Copyright (C) 2011 VMware, Inc.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to
+deal in the Software without restriction, including without limitation the
+rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+sell copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+IN THE SOFTWARE.
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..7b31b05
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,13 @@
+all: myclient myservice monitor notifier
+
+myclient: myclient.c
+myservice: myservice.c
+monitor: monitor.c
+notifier: notifier.c
+
+clean:
+	$(RM) myclient myservice monitor notifier
+
+CFLAGS=-Wall
+LDFLAGS=-lzmq
+
diff --git a/README.markdown b/README.markdown
new file mode 100644
index 0000000..f0aa46a
--- /dev/null
+++ b/README.markdown
@@ -0,0 +1,15 @@
+# Flexible topology demonstration
+
+This is a demonstration of transparently modifying a topology using ZeroMQ and
+DNS. More documentation is forthcoming, once I get around to translating it
+from the original OOo document.
+
+Prerequisites needed to get this working:
+
+- zeromq built with `dns://` support, from the `dns` branch of
+  https://github.com/mato/libzmq
+- a machine you can run a test installation of BIND 9 on
+- Ruby 1.9
+- ffi-rzmq from https://github.com/chuckremes/ffi-rzmq/
+
+Martin Lucina <martin@lucina.net>, November 2011
diff --git a/console.rb b/console.rb
new file mode 100755
index 0000000..6589b8a
--- /dev/null
+++ b/console.rb
@@ -0,0 +1,474 @@
+#!/usr/bin/env ruby
+#
+#  console.rb: Console GUI component.
+#
+#  Copyright (C) 2011 VMware, Inc.
+# 
+#  Permission is hereby granted, free of charge, to any person obtaining a copy
+#  of this software and associated documentation files (the "Software"), to deal
+#  in the Software without restriction, including without limitation the rights
+#  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+#  copies of the Software, and to permit persons to whom the Software is
+#  furnished to do so, subject to the following conditions:
+#  
+#  The above copyright notice and this permission notice shall be included in
+#  all copies or substantial portions of the Software.
+# 
+#  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+#  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+#  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+#  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+#  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+#  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+#  THE SOFTWARE.
+
+#  Apologies in advance for the state of this code, my Ruby/Tk-fu is really not
+#  up to scratch. The liberal use of $global_variables is to get things working
+#  correctly from Tk callbacks, if you know a better way to make this work
+#  please let me know.
+
+require 'tk'
+require 'ffi-rzmq'
+require 'thread'
+
+#  Convenience method to raise exception on ffi-rzmq error
+def raise_if_error(rc)
+  unless ZMQ::Util.resultcode_ok?(rc)
+    raise "ZMQ Error: #{ZMQ::Util.error_string}"
+  end
+end
+
+#  Callable on any Tk widget, adds get/set methods for mytag and mytype,
+#  allowing us to keep track of what is what when we get callback events.
+def make_taggable(widget)
+  widget.instance_eval do
+    @mytag = nil
+    @mytype = nil
+    def mytag
+      @mytag
+    end
+    def mytag=(tag)
+      @mytag = tag
+    end
+    def mytype
+      @mytype
+    end
+    def mytype=(type)
+      @mytype = type
+    end
+  end
+end
+
+#  Build out the GUI.
+def build_gui
+  $root = TkRoot.new { title "Console" }
+  $workspace = TkFrame.new($root) {
+      relief 'sunken'
+      borderwidth '2'
+    }
+  $workspace.grid :column => 0, :row => 0, :columnspan => 2, :sticky => 'nsew'
+  $buttons = TkFrame.new($root)
+  $buttons.grid :column => 0, :row => 1, :columnspan => 2, :sticky => 'nsew'
+  $start = TkButton.new($buttons) {
+      text 'Start'
+      state :disabled
+      command proc {
+        host = $selected_item.mytag
+        start_service_dialog(host)
+      }
+    }
+  $start.pack :padx => 10, :side => :left
+  $stop = TkButton.new($buttons) {
+      text 'Stop'
+      state :disabled
+      command proc {
+        service = $selected_item.mytag
+        host = $selected_item.winfo_parent.mytag
+        result = Tk::messageBox :type => :yesno,
+          :message => "Are you sure you wish to stop the service " + \
+            "'#{service}' on host '#{host}'?",
+          :icon => :question,
+          :title => "Stop service"
+        stop_service(service, host) if result == 'yes'
+      }
+    }
+  $stop.pack :padx => 10, :side => :left
+  $restart = TkButton.new($buttons) {
+      text 'Restart'
+      state :disabled
+      command proc {
+        service = $selected_item.mytag
+        host = $selected_item.winfo_parent.mytag
+        restart_service_dialog(host, service)
+      }
+    }
+  $restart.pack :padx => 10, :side => :left
+  $dns = TkButton.new($buttons) {
+      text 'Update DNS'
+      command proc {
+        update_dns_dialog()
+      }
+    }
+  $dns.pack :padx => 10, :side => :left
+  $exit = TkButton.new($buttons) {
+      text 'Exit'
+      command proc {
+        result = Tk::messageBox :type => :yesno,
+          :message => "Are you sure you want to exit?",
+          :icon => :question,
+          :title => "Confirm exit"
+        exit if result == 'yes'
+      }
+    }
+  $exit.pack :side => :left
+  $console = TkListbox.new($root) { 
+      height 10
+      width 60
+      yscrollcommand proc { |*args| $console_sb.set(*args) }
+    }
+  $console.grid :column => 0, :row => 2, :sticky => 'nwes'
+  $console_sb = TkScrollbar.new($root) {
+      orient :vertical
+      command proc { |*args| $console.yview(*args) }
+    }
+  $console_sb.grid :column => 1, :row => 2, :sticky => 'ns'
+  TkGrid.columnconfigure $root, 0, :weight => 1, :minsize => 600
+  TkGrid.rowconfigure $root, 0, :weight => 1, :minsize => 400
+end
+
+#  DNS Update dialog GUI
+def update_dns_dialog
+  w = TkToplevel.new { title "Update DNS record" }
+  w.wm_transient($root)
+  l = TkLabel.new(w) { text "Record" }
+  r = TkEntry.new(w) { width 15 }
+  r.focus
+  l2 = TkLabel.new(w) { text "Value" }
+  v = TkEntry.new(w) { width 15 }
+  ok = TkButton.new(w) {
+    text "OK"
+    command proc {
+      if r.get.length > 0 && v.get.length > 0
+        result = `./nsupdate-script #{r.get} #{v.get}`
+        result.chomp
+        console_add("Updating DNS record '#{r.get}' to value '#{v.get}': #{result}")
+        w.destroy
+      end
+      }
+    default :active
+    }
+  cancel = TkButton.new(w) { text "Cancel"; command proc { w.destroy } }
+  w.bind('Return') { ok.invoke }
+  w.bind('Escape') { cancel.invoke }
+  l.grid :column => 0, :row => 0, :padx => 10, :pady => 10
+  r.grid :column => 1, :row => 0, :padx => 10, :pady => 10
+  l2.grid :column => 0, :row => 1, :padx => 10, :pady => 10
+  v.grid :column => 1, :row => 1, :padx => 10, :pady => 10
+  ok.grid :column => 0, :row => 2, :padx => 10, :pady => 10
+  cancel.grid :column => 1, :row => 2, :padx => 10, :pady => 10
+  w.grab
+  w.tkwait
+end
+
+#  Start Service dialog GUI
+def start_service_dialog(host)
+  w = TkToplevel.new { title "Start service on #{host}" }
+  w.wm_transient($root)
+  l = TkLabel.new(w) { text "Command" }
+  e = TkEntry.new(w) { width 40 }
+  e.focus
+  ok = TkButton.new(w) {
+    text "OK"
+    command proc {
+      if e.get.length > 0
+        start_service(host, e.get)
+        w.destroy
+      end
+      }
+    default :active
+    }
+  cancel = TkButton.new(w) { text "Cancel"; command proc { w.destroy } }
+  w.bind('Return') { ok.invoke }
+  w.bind('Escape') { cancel.invoke }
+  l.grid :column => 0, :row => 0, :padx => 10, :pady => 10
+  e.grid :column => 1, :row => 0, :padx => 10, :pady => 10
+  ok.grid :column => 0, :row => 1, :padx => 10, :pady => 10
+  cancel.grid :column => 1, :row => 1, :padx => 10, :pady => 10
+  w.grab
+  w.tkwait
+end
+
+#  Restart service dialog GUI
+def restart_service_dialog(host, service)
+  w = TkToplevel.new { title "Restart service #{service} on #{host}" }
+  w.wm_transient($root)
+  l = TkLabel.new(w) { text "Command" }
+  e = TkEntry.new(w) { width 40 }
+  e.set($hosts[host][:services][service][:command])
+  e.focus
+  ok = TkButton.new(w) {
+    text "OK"
+    command proc {
+      if e.get.length > 0
+        stop_service(service, host)
+        start_service(host, e.get)
+        w.destroy
+      end
+      }
+    default :active
+    }
+  cancel = TkButton.new(w) { text "Cancel"; command proc { w.destroy } }
+  w.bind('Return') { ok.invoke }
+  w.bind('Escape') { cancel.invoke }
+  l.grid :column => 0, :row => 0, :padx => 10, :pady => 10
+  e.grid :column => 1, :row => 0, :padx => 10, :pady => 10
+  ok.grid :column => 0, :row => 1, :padx => 10, :pady => 10
+  cancel.grid :column => 1, :row => 1, :padx => 10, :pady => 10
+  w.grab
+  w.tkwait
+end
+
+#  Start service 'command' on 'host'
+def start_service(host, command)
+  console_add("Starting command '#{command}' on host #{host}");
+  s = $ctx.socket(ZMQ::PUSH)
+  rc = s.connect("tcp://#{host}:7772")
+  raise_if_error(rc)
+  rc = s.send_string("START #{command}")
+  raise_if_error(rc)
+  rc = s.close
+  raise_if_error(rc)
+end
+
+#  Stop service 'service' on 'host'
+def stop_service(service, host)
+  console_add("Stopping service: #{service} on host: #{host}")
+  s = $ctx.socket(ZMQ::PUSH)
+  rc = s.connect("tcp://#{host}:7772")
+  raise_if_error(rc)
+  rc = s.send_string("STOP #{service}")
+  raise_if_error(rc)
+  rc = s.close
+  raise_if_error(rc)
+end
+
+#  Log text to console widget
+def console_add(msg)
+  $console.insert 'end', Time.now.to_s + ' ' + msg
+  $console.yview 'end'
+end
+
+#  Select an item in the console, highlights it and updates available
+#  action buttons
+def select_item(new)
+  old = $selected_item
+  if old
+    target = old.labelwidget if old.mytype == :host
+    target = old if old.mytype == :service
+    target.background('#d9d9d9')
+  end
+  if new.mytype == :host
+    new.labelwidget.background('green')
+    $start.state(:normal)
+    $stop.state(:disabled)
+    $restart.state(:disabled)
+  elsif new.mytype == :service
+    new.background('green')
+    $start.state(:disabled)
+    $stop.state(:normal)
+    $restart.state(:normal)
+  end
+  $selected_item = new
+end
+
+#  Run periodically from Tk Timer to pull interesting messages from notifier
+#  and update the GUI accordingly.
+def update
+  begin
+    msg = ''
+    rc = 0
+    loop do
+      $semaphore.synchronize do
+        rc = $notifier_sock.recv_string(msg, ZMQ::DONTWAIT)
+      end
+      if rc < 0
+        break if ZMQ::Util.errno == ZMQ::EAGAIN
+        raise_if_error(rc)
+      end
+      if msg =~ /^WATCHDOG (\w+) (\w+) ([\w\.]+) ?(.*)?$/
+        verb = $1
+        host = $2
+        timestamp = $3.to_f
+        command = $4
+        if verb == 'ALIVE'
+          if $hosts.has_key?(host)
+            $hosts[host][:last_seen] = timestamp
+          else
+            label = TkLabel.new($workspace) { text host }
+            make_taggable(label)
+            label.mytag = host
+            label.mytype = :host
+            host_widget = TkLabelFrame.new($workspace) {
+              labelwidget label
+              width '4c'
+              height '4c'
+              relief 'raised'
+              padx 10
+              pady 10
+            }
+            make_taggable(host_widget)
+            host_widget.mytag = host
+            host_widget.mytype = :host
+            host_widget.pack :side => :left,:anchor => 'nw',
+              :padx => 10, :pady => 10
+            host_widget.cursor("hand2")
+            label.cursor("hand2")
+            label.bind("1", proc { |event|
+              host = event.widget.mytag
+              real_widget = $hosts[host][:widget]
+              select_item(real_widget)
+              console_add("Selected host: #{host}")
+              })
+            host_widget.bind("1", proc { |event|
+              select_item(event.widget)
+              console_add("Selected host: #{event.widget.mytag}")
+              })
+            $hosts[host] = {}
+            $hosts[host][:widget] = host_widget
+            $hosts[host][:services] = {}
+            $hosts[host][:last_seen] = timestamp
+            console_add("Registered host: #{host}")
+          end
+        elsif verb == 'RUNNING'
+          service = command.split()[0]
+          svcs = $hosts[host][:services]
+          if svcs.has_key?(service)
+            svcs[service][:last_seen] = timestamp
+          else
+            svcs[service] = {}
+            svcs[service][:command] = command
+            svcs[service][:last_seen] = timestamp
+            host_widget = $hosts[host][:widget]
+            service_widget = TkLabel.new(host_widget) { 
+              text service
+              padx '0.25c'
+              pady '0.25c'
+              }
+            make_taggable(service_widget)
+            service_widget.mytype = :service
+            service_widget.mytag = service
+            service_widget.pack { fill 'both' }
+            service_widget.cursor("hand2")
+            service_widget.bind("1", proc { |event|
+              select_item(event.widget)
+              console_add("Selected service: #{event.widget.mytag}")
+              })
+            svcs[service][:widget] = service_widget
+            console_add("Registered service: #{service} on host: #{host}")
+          end
+        end
+      elsif msg =~ /^VALUE (\w+) (\w+) (.*)$/
+        host = $1
+        service = $2
+        value = $3
+        if $hosts.has_key?(host) && $hosts[host][:services].has_key?(service)
+          widget = $hosts[host][:services][service][:widget]
+          widget.text(widget.mytag + "\n" + value)
+        end
+      end
+    end
+  rescue => exception
+    print exception, "\n"
+    print exception.backtrace.join("\n\t from "), "\n"
+    Process.abort
+  end
+end
+
+#  Run periodically from Tk Timer to reap dead hosts/services from GUI.
+def reaper
+  begin
+    current_time = Time.now.to_f
+    $hosts.each do |key, host|
+      if current_time - host[:last_seen] > 2
+        host[:services].each do |key, service|
+          if $selected_item == service[:widget]
+            $start.state(:disabled)
+            $stop.state(:disabled)
+            $restart.state(:disabled)
+            $selected_item = nil
+          end
+          service[:widget].destroy
+          host[:services].delete(key)
+        end
+        if $selected_item == host[:widget]
+          $start.state(:disabled)
+          $stop.state(:disabled)
+          $restart.state(:disabled)
+          $selected_item = nil
+        end
+        host[:widget].destroy
+        $hosts.delete(key)
+        console_add("Removed host: #{key}")
+      else
+        host[:services].each do |key, service|
+          if current_time - service[:last_seen] > 2
+            if $selected_item == service[:widget]
+              $start.state(:disabled)
+              $stop.state(:disabled)
+              $restart.state(:disabled)
+              $selected_item = nil
+            end
+            service[:widget].destroy
+            host[:services].delete(key)
+            console_add("Removed service: #{key}")
+          end
+        end
+      end
+    end
+  rescue => exception
+    print exception, "\n"
+    print exception.backtrace.join("\n\t from "), "\n"
+    Process.abort
+  end
+end
+
+#
+#  Main program
+#
+
+#  Globals used by GUI
+#  ZMQ context
+$ctx = ZMQ::Context.new()
+#  Currently selected item (host/service)
+$selected_item = nil
+#  Map of hosts and their services
+$hosts = {}
+
+#  Parse arguments
+unless ARGV[0]
+  print "usage: console.rb <notifier-host>\n"
+  exit 1
+end
+notifier_ep = "tcp://#{ARGV[0]}:7771"
+
+#  Create and connect to notifier socket. Synchronized to allow migration to
+#  GUI callback thread.
+$semaphore = Mutex.new
+$semaphore.synchronize do
+  $notifier_sock = $ctx.socket(ZMQ::SUB)
+  rc = $notifier_sock.setsockopt(ZMQ::SUBSCRIBE, '')
+  raise_if_error(rc)
+  rc = $notifier_sock.connect(notifier_ep)
+  raise_if_error(rc)
+end
+
+#  Build and update GUI immediately on startup
+build_gui
+update
+
+#  Setup timers and go into Tk mainloop
+#  Update GUI/reap dead objects every 500ms
+TkTimer.new(500, -1, proc { update }).start
+TkTimer.new(500, -1, proc { reaper }).start
+Tk.mainloop
+
diff --git a/db.test b/db.test
new file mode 100644
index 0000000..c2e2879
--- /dev/null
+++ b/db.test
@@ -0,0 +1,13 @@
+$ORIGIN .
+$TTL 300	; 5 minutes
+test			IN SOA	localhost. root.localhost. (
+				1          ; serial
+				604800     ; refresh (1 week)
+				86400      ; retry (1 day)
+				2419200    ; expire (4 weeks)
+				300        ; minimum (5 minutes)
+				)
+			NS	localhost.
+$ORIGIN test.
+$TTL 10	; 10 seconds
+myservice		TXT	""
diff --git a/monitor.c b/monitor.c
new file mode 100644
index 0000000..25c7867
--- /dev/null
+++ b/monitor.c
@@ -0,0 +1,175 @@
+/* monitor.c: Monitoring component.
+ *
+ * Copyright (C) 2011 VMware, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include <arpa/inet.h>
+#include <assert.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <zmq.h>
+
+#define ERR_EXIT(what) { \
+    fprintf (stderr, "error in %s: %s\n", what, zmq_strerror (errno)); \
+    exit (EXIT_FAILURE); \
+    }
+
+int main (int argc, char *argv [])
+{
+    void *ctx;
+    const char *client_ep, *service_ep, *notifier_host;
+    char notifier_ep[1024];
+    char msg_buf[1024];
+    char hostname[1024];
+    void *client_socket, *service_socket, *notifier_socket;
+    int rc;
+   
+    if (argc != 4) {
+        fprintf (stderr,
+	    "usage: monitor "\
+            "<notifier-host> <client-bind-ep> <service-connect-ep>\n");
+	exit (EXIT_FAILURE);
+    }
+    notifier_host = argv [1];
+    sprintf (notifier_ep, "tcp://%s:7770", notifier_host);
+    client_ep = argv [2];
+    service_ep = argv [3];
+
+    rc = gethostname(hostname, sizeof hostname);
+    assert (rc == 0);
+
+    ctx = zmq_init (1);
+    if (!ctx)
+	ERR_EXIT ("zmq_init");
+
+    client_socket = zmq_socket (ctx, ZMQ_XPUB);
+    if (!client_socket)
+	ERR_EXIT ("zmq_socket");
+
+    rc = zmq_bind (client_socket, client_ep);
+    if (rc < 0)
+	ERR_EXIT ("zmq_bind");
+
+    service_socket = zmq_socket (ctx, ZMQ_XSUB);
+    if (!service_socket)
+	ERR_EXIT ("zmq_socket");
+    
+    rc = zmq_connect (service_socket, service_ep);
+    if (rc < 0)
+	ERR_EXIT ("zmq_connect");
+
+    notifier_socket = zmq_socket (ctx, ZMQ_PUB);
+    if (!notifier_socket)
+	ERR_EXIT ("zmq_socket");
+    
+    rc = zmq_connect (notifier_socket, notifier_ep);
+    if (rc < 0)
+	ERR_EXIT ("zmq_bind");
+
+    int64_t more;
+    size_t moresz;
+    uint32_t seq_no = 0;
+    
+    zmq_msg_t msg;
+    rc = zmq_msg_init (&msg);
+    assert (rc == 0);
+
+    zmq_pollitem_t items [2];
+    items [0].socket = client_socket;
+    items [0].fd = 0;
+    items [0].events = ZMQ_POLLIN;
+    items [0].revents = 0;
+    items [1].socket = service_socket;
+    items [1].fd = 0;
+    items [1].events = ZMQ_POLLIN;
+    items [1].revents = 0;
+
+    while (1) {
+
+        /*  Wait for either upstream subscriptions or messages. */
+        rc = zmq_poll (&items [0], 2, -1);
+        if (rc < 0)
+	    ERR_EXIT ("zmq_poll");
+
+        /*  Process an upstream subscription. */
+        if (items [0].revents & ZMQ_POLLIN) {
+            while (1) {
+
+                rc = zmq_recvmsg (client_socket, &msg, 0);
+                if (rc < 0)
+		    ERR_EXIT ("zmq_recvmsg");
+                
+                moresz = sizeof (more);
+                rc = zmq_getsockopt (client_socket, ZMQ_RCVMORE, &more, &moresz);
+                if (rc < 0)
+		    ERR_EXIT ("zmq_getsockopt");
+
+                rc = zmq_sendmsg (service_socket, &msg, more ? ZMQ_SNDMORE : 0);
+                if (rc < 0)
+		    ERR_EXIT ("zmq_sendmsg");
+
+                if (!more)
+                    break;
+            }
+        }
+
+        /*  Process a downstream message. */
+        if (items [1].revents & ZMQ_POLLIN) {
+            while (1) {
+
+                rc = zmq_recvmsg (service_socket, &msg, 0);
+                if (rc < 0)
+		    ERR_EXIT ("zmq_recvmsg");
+                
+                moresz = sizeof (more);
+                rc = zmq_getsockopt (service_socket, ZMQ_RCVMORE, &more, &moresz);
+                if (rc < 0)
+		    ERR_EXIT ("zmq_getsockopt");
+
+                rc = zmq_sendmsg (client_socket, &msg, more ? ZMQ_SNDMORE : 0);
+                if (rc < 0)
+		    ERR_EXIT ("zmq_sendmsg");
+
+                if (!more) {
+		    /*  For each complete message, publish the sequence number
+		        (# of messages sent) to the notifier socket. */
+                    uint32_t seq_no_wire;
+
+                    seq_no++;
+                    seq_no_wire = htonl (seq_no);
+                    sprintf(msg_buf, "VALUE %s monitor %u", hostname, seq_no);
+                    rc = zmq_send (notifier_socket, msg_buf, strlen(msg_buf), 0);
+		    if (rc != strlen(msg_buf))
+			ERR_EXIT ("zmq_send");
+
+                    break;
+                }
+            }
+        }
+
+    }
+
+    exit (EXIT_SUCCESS);
+}
+
diff --git a/myclient.c b/myclient.c
new file mode 100644
index 0000000..5eba6a7
--- /dev/null
+++ b/myclient.c
@@ -0,0 +1,78 @@
+/* myclient.c: "External" client component.
+ *
+ * Copyright (C) 2011 VMware, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <zmq.h>
+#include <zmq_utils.h>
+
+#define ERR_EXIT(what) { \
+    fprintf (stderr, "error in %s: %s\n", what, zmq_strerror (errno)); \
+    exit (EXIT_FAILURE); \
+    }
+
+int main (int argc, char *argv [])
+{
+    const char *connect_to = "dns://myservice.test";
+    void *ctx;
+    void *s;
+    int rc;
+    zmq_msg_t msg;
+
+    if (argc != 1) {
+        fprintf (stderr, "usage: myclient\n");
+        exit (EXIT_FAILURE);
+    }
+
+    ctx = zmq_init (1);
+    if (!ctx)
+	ERR_EXIT ("zmq_init");
+
+    s = zmq_socket (ctx, ZMQ_SUB);
+    if (!s)
+	ERR_EXIT ("zmq_socket");
+
+    rc = zmq_setsockopt (s, ZMQ_SUBSCRIBE, "", 0);
+    if (rc != 0)
+	ERR_EXIT ("zmq_setsockopt");
+
+    rc = zmq_connect (s, connect_to);
+    if (rc != 0)
+	ERR_EXIT ("zmq_connect");
+
+    rc = zmq_msg_init (&msg);
+    if (rc != 0)
+	ERR_EXIT ("zmq_msg_init");
+
+    for (;;) {
+        rc = zmq_recvmsg (s, &msg, 0);
+        if (rc < 0)
+	    ERR_EXIT ("zmq_recvmsg");
+
+        printf ("+");
+        fflush (stdout);
+    }
+
+    exit (EXIT_SUCCESS);
+}
+
diff --git a/myservice.c b/myservice.c
new file mode 100644
index 0000000..89a031b
--- /dev/null
+++ b/myservice.c
@@ -0,0 +1,70 @@
+/* myservice.c: Service (publisher) component.
+ *
+ * Copyright (C) 2011 VMware, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <zmq.h>
+
+#define ERR_EXIT(what) { \
+    fprintf (stderr, "error in %s: %s\n", what, zmq_strerror (errno)); \
+    exit (EXIT_FAILURE); \
+    }
+
+int main (int argc, char *argv [])
+{
+    const char *bind_to;
+    const char *message = "MESSAGE";
+    void *ctx;
+    void *s;
+    int rc;
+
+    if (argc != 2) {
+        fprintf (stderr, "usage: myservice <service-bind-ep>\n");
+	exit (EXIT_FAILURE);
+    }
+    bind_to = argv [1];
+
+    ctx = zmq_init (1);
+    if (!ctx)
+	ERR_EXIT ("zmq_init");
+
+    s = zmq_socket (ctx, ZMQ_PUB);
+    if (!s)
+	ERR_EXIT ("zmq_socket");
+
+    rc = zmq_bind (s, bind_to);
+    if (rc != 0)
+	ERR_EXIT ("zmq_bind");
+
+    for (;;) {
+        rc = zmq_send (s, message, sizeof message, 0);
+        if (rc != sizeof message)
+	    ERR_EXIT ("zmq_send");
+
+        sleep (1);
+    }
+
+    exit (EXIT_SUCCESS);
+}
diff --git a/named.conf.add b/named.conf.add
new file mode 100644
index 0000000..a216588
--- /dev/null
+++ b/named.conf.add
@@ -0,0 +1,12 @@
+key test {
+	algorithm HMAC-MD5;
+	secret "iAKtzkTWm+dOJjjNEHSHMTivZe6vtzzlRfFoP4yM20oCEWRrt6oW+XhzU1b3NJETErQo3xNALU6gsPHGzGYghg==";
+};
+
+zone "test" {
+	type master;
+	file "db.test";
+	update-policy {
+		grant test name myservice.test. TXT;
+	};
+};
diff --git a/notifier.c b/notifier.c
new file mode 100644
index 0000000..775cf50
--- /dev/null
+++ b/notifier.c
@@ -0,0 +1,145 @@
+/* monitor.c: Notifier (console mini-broker) component.
+ *
+ * Copyright (C) 2011 VMware, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include <arpa/inet.h>
+#include <assert.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <zmq.h>
+
+#define ERR_EXIT(what) { \
+    fprintf (stderr, "error in %s: %s\n", what, zmq_strerror (errno)); \
+    exit (EXIT_FAILURE); \
+    }
+
+int main (int argc, char *argv [])
+{
+    void *ctx;
+    const char *app_ep = "tcp://*:7770",
+               *console_ep = "tcp://*:7771";
+    void *app_socket, *console_socket;
+    int rc;
+   
+    if (argc != 1) {
+        fprintf (stderr, "usage: notifier\n");
+        fprintf (stderr, "  binds to ports 7770 (application port)\n");
+        fprintf (stderr, "             and 7771 (console port)\n");
+	exit (EXIT_FAILURE);
+    }
+
+    ctx = zmq_init (1);
+    if (!ctx)
+	ERR_EXIT ("zmq_init");
+
+    app_socket = zmq_socket (ctx, ZMQ_XSUB);
+    if (!app_socket)
+	ERR_EXIT ("zmq_socket");
+
+    rc = zmq_bind (app_socket, app_ep);
+    if (rc < 0)
+	ERR_EXIT ("zmq_bind");
+
+    console_socket = zmq_socket (ctx, ZMQ_XPUB);
+    if (!console_socket)
+	ERR_EXIT ("zmq_socket");
+    
+    rc = zmq_bind (console_socket, console_ep);
+    if (rc < 0)
+	ERR_EXIT ("zmq_bind");
+
+    int64_t more;
+    size_t moresz;
+    
+    zmq_msg_t msg;
+    rc = zmq_msg_init (&msg);
+    assert (rc == 0);
+
+    zmq_pollitem_t items [2];
+    items [0].socket = app_socket;
+    items [0].fd = 0;
+    items [0].events = ZMQ_POLLIN;
+    items [0].revents = 0;
+    items [1].socket = console_socket;
+    items [1].fd = 0;
+    items [1].events = ZMQ_POLLIN;
+    items [1].revents = 0;
+
+    while (1) {
+
+        /*  Wait for either upstream subscriptions or messages. */
+        rc = zmq_poll (&items [0], 2, -1);
+        if (rc < 0)
+	    ERR_EXIT ("zmq_poll");
+
+        /*  Process an upstream subscription. */
+        if (items [0].revents & ZMQ_POLLIN) {
+            while (1) {
+
+                rc = zmq_recvmsg (app_socket, &msg, 0);
+                if (rc < 0)
+		    ERR_EXIT ("zmq_recvmsg");
+                
+                moresz = sizeof (more);
+                rc = zmq_getsockopt (app_socket, ZMQ_RCVMORE, &more, &moresz);
+                if (rc < 0)
+		    ERR_EXIT ("zmq_getsockopt");
+
+                rc = zmq_sendmsg (console_socket, &msg, more ? ZMQ_SNDMORE : 0);
+                if (rc < 0)
+		    ERR_EXIT ("zmq_sendmsg");
+
+                if (!more)
+                    break;
+            }
+        }
+
+        /*  Process a downstream message. */
+        if (items [1].revents & ZMQ_POLLIN) {
+            while (1) {
+
+                rc = zmq_recvmsg (console_socket, &msg, 0);
+                if (rc < 0)
+		    ERR_EXIT ("zmq_recvmsg");
+                
+                moresz = sizeof (more);
+                rc = zmq_getsockopt (console_socket, ZMQ_RCVMORE, &more, &moresz);
+                if (rc < 0)
+		    ERR_EXIT ("zmq_getsockopt");
+
+                rc = zmq_sendmsg (app_socket, &msg, more ? ZMQ_SNDMORE : 0);
+                if (rc < 0)
+		    ERR_EXIT ("zmq_sendmsg");
+
+                if (!more) {
+                    break;
+                }
+            }
+        }
+
+    }
+
+    exit (EXIT_SUCCESS);
+}
+
diff --git a/nsupdate-script b/nsupdate-script
new file mode 100755
index 0000000..023b161
--- /dev/null
+++ b/nsupdate-script
@@ -0,0 +1,32 @@
+#!/bin/sh
+#
+#  nsupdate-script does the actuall call to 'nsupdate'. It is called by the
+#  console and returns 'OK' or 'ERROR' to standard output.
+#
+#  Edit the address below to point to your DNS server IP.
+#
+DNS_SERVER="192.168.1.11"
+#
+#
+#
+
+if [ $# -ne 2 ]; then
+    echo "usage: nsupdate-script <record> <value>" 1>&2
+    exit 1
+fi
+RECORD=$1
+VALUE=$2
+
+nsupdate -k ./nsupdate.test <<EOT
+server ${DNS_SERVER}
+update delete ${RECORD} TXT
+update add ${RECORD} 10 TXT "${VALUE}"
+send
+EOT
+
+if [ $? -ne 0 ]; then
+    echo "ERROR"
+    exit 1
+fi
+echo "OK"
+exit 0
diff --git a/nsupdate.key b/nsupdate.key
new file mode 100644
index 0000000..bb2923c
--- /dev/null
+++ b/nsupdate.key
@@ -0,0 +1,7 @@
+Private-key-format: v1.3
+Algorithm: 157 (HMAC_MD5)
+Key: iAKtzkTWm+dOJjjNEHSHMTivZe6vtzzlRfFoP4yM20oCEWRrt6oW+XhzU1b3NJETErQo3xNALU6gsPHGzGYghg==
+Bits: AAA=
+Created: 20111019163300
+Publish: 20111019163300
+Activate: 20111019163300
diff --git a/nsupdate.test.key b/nsupdate.test.key
new file mode 100644
index 0000000..3a418a5
--- /dev/null
+++ b/nsupdate.test.key
@@ -0,0 +1 @@
+test. IN KEY 512 3 157 iAKtzkTWm+dOJjjNEHSHMTivZe6vtzzlRfFoP4yM20oCEWRrt6oW+Xhz U1b3NJETErQo3xNALU6gsPHGzGYghg==
diff --git a/nsupdate.test.private b/nsupdate.test.private
new file mode 100644
index 0000000..bb2923c
--- /dev/null
+++ b/nsupdate.test.private
@@ -0,0 +1,7 @@
+Private-key-format: v1.3
+Algorithm: 157 (HMAC_MD5)
+Key: iAKtzkTWm+dOJjjNEHSHMTivZe6vtzzlRfFoP4yM20oCEWRrt6oW+XhzU1b3NJETErQo3xNALU6gsPHGzGYghg==
+Bits: AAA=
+Created: 20111019163300
+Publish: 20111019163300
+Activate: 20111019163300
diff --git a/test-fakehost.rb b/test-fakehost.rb
new file mode 100755
index 0000000..2fa0a32
--- /dev/null
+++ b/test-fakehost.rb
@@ -0,0 +1,54 @@
+#!/usr/bin/env ruby
+#
+#  test-fakehost.rb: Simulate a fake host to excersize console GUI.
+#
+#  Copyright (C) 2011 VMware, Inc.
+# 
+#  Permission is hereby granted, free of charge, to any person obtaining a copy
+#  of this software and associated documentation files (the "Software"), to deal
+#  in the Software without restriction, including without limitation the rights
+#  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+#  copies of the Software, and to permit persons to whom the Software is
+#  furnished to do so, subject to the following conditions:
+#  
+#  The above copyright notice and this permission notice shall be included in
+#  all copies or substantial portions of the Software.
+# 
+#  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+#  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+#  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+#  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+#  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+#  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+#  THE SOFTWARE.
+
+require 'ffi-rzmq'
+
+trap("INT") { exit }
+trap("TERM") { exit }
+def raise_if_error(rc)
+  unless ZMQ::Util.resultcode_ok?(rc)
+    raise "ZMQ Error: #{ZMQ::Util.error_string}"
+  end
+end
+
+if ARGV.length != 2
+  print "usage: test-fakehost.rb <notifier-connect-ep> <fake-host-name>\n"
+  exit 1
+end
+
+notifier_ep = ARGV.shift
+host = ARGV.shift
+
+ctx = ZMQ::Context.new()
+notifier_sock = ctx.socket(ZMQ::PUB)
+rc = notifier_sock.connect(notifier_ep)
+raise_if_error(rc)
+
+loop do
+    status = "WATCHDOG ALIVE #{host} " + Time.now.to_f.to_s
+    rc = notifier_sock.send_string(status)
+    raise_if_error(rc)
+    sleep 1
+end
+
diff --git a/test-notifier.rb b/test-notifier.rb
new file mode 100755
index 0000000..1adeb20
--- /dev/null
+++ b/test-notifier.rb
@@ -0,0 +1,55 @@
+#!/usr/bin/env ruby
+#
+#  test-notifier.rb: Dump all messages received from notifier.
+#
+#  Copyright (C) 2011 VMware, Inc.
+# 
+#  Permission is hereby granted, free of charge, to any person obtaining a copy
+#  of this software and associated documentation files (the "Software"), to deal
+#  in the Software without restriction, including without limitation the rights
+#  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+#  copies of the Software, and to permit persons to whom the Software is
+#  furnished to do so, subject to the following conditions:
+#  
+#  The above copyright notice and this permission notice shall be included in
+#  all copies or substantial portions of the Software.
+# 
+#  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+#  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+#  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+#  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+#  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+#  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+#  THE SOFTWARE.
+
+require 'ffi-rzmq'
+
+trap("INT") { exit }
+trap("TERM") { exit }
+def raise_if_error(rc)
+  unless ZMQ::Util.resultcode_ok?(rc)
+    raise "ZMQ Error: #{ZMQ::Util.error_string}"
+  end
+end
+
+unless ARGV[0]
+  print "usage: test-notifier.rb <notifier-host>\n"
+  exit 1
+end
+
+notifier_ep = "tcp://#{ARGV[0]}:7771"
+
+ctx = ZMQ::Context.new()
+notifier_sock = ctx.socket(ZMQ::SUB)
+rc = notifier_sock.setsockopt(ZMQ::SUBSCRIBE, '')
+raise_if_error(rc)
+rc = notifier_sock.connect(notifier_ep)
+raise_if_error(rc)
+
+msg = ''
+loop do
+  rc = notifier_sock.recv_string(msg, 0)
+  raise_if_error(rc)
+  print "[#{Time.now}] #{msg}\n"
+end
+
diff --git a/test-wdclient.rb b/test-wdclient.rb
new file mode 100755
index 0000000..bd162f0
--- /dev/null
+++ b/test-wdclient.rb
@@ -0,0 +1,51 @@
+#!/usr/bin/env ruby
+#
+#  test-wdclient.rb: Test watchdog by sending arbitrary command messages.
+#
+#  Copyright (C) 2011 VMware, Inc.
+# 
+#  Permission is hereby granted, free of charge, to any person obtaining a copy
+#  of this software and associated documentation files (the "Software"), to deal
+#  in the Software without restriction, including without limitation the rights
+#  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+#  copies of the Software, and to permit persons to whom the Software is
+#  furnished to do so, subject to the following conditions:
+#  
+#  The above copyright notice and this permission notice shall be included in
+#  all copies or substantial portions of the Software.
+# 
+#  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+#  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+#  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+#  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+#  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+#  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+#  THE SOFTWARE.
+
+require 'ffi-rzmq'
+
+def raise_if_error(rc)
+  unless ZMQ::Util.resultcode_ok?(rc)
+    raise "ZMQ Error: #{ZMQ::Util.error_string}"
+  end
+end
+
+if ARGV.length < 2
+  print "usage: test-wdclient <command-ep> <command> <args...>\n"
+  exit 1
+end
+
+command_ep = ARGV.shift
+command = ARGV.shift
+args = ARGV.join(' ')
+
+ctx = ZMQ::Context.new()
+command_sock = ctx.socket(ZMQ::PUSH)
+rc = command_sock.connect(command_ep)
+raise_if_error(rc)
+
+rc = command_sock.send_string(command + ' ' + args)
+raise_if_error(rc)
+rc = command_sock.close
+raise_if_error(rc)
+
diff --git a/watchdog.rb b/watchdog.rb
new file mode 100755
index 0000000..e6b82e8
--- /dev/null
+++ b/watchdog.rb
@@ -0,0 +1,121 @@
+#!/usr/bin/env ruby
+#
+#  watchdog.rb: Watchdog component.
+#
+#  Copyright (C) 2011 VMware, Inc.
+# 
+#  Permission is hereby granted, free of charge, to any person obtaining a copy
+#  of this software and associated documentation files (the "Software"), to deal
+#  in the Software without restriction, including without limitation the rights
+#  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+#  copies of the Software, and to permit persons to whom the Software is
+#  furnished to do so, subject to the following conditions:
+#  
+#  The above copyright notice and this permission notice shall be included in
+#  all copies or substantial portions of the Software.
+# 
+#  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+#  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+#  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+#  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+#  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+#  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+#  THE SOFTWARE.
+
+require 'thread'
+require 'ffi-rzmq'
+require 'socket'
+
+trap("INT") { exit }
+trap("TERM") { exit }
+def raise_if_error(rc)
+  unless ZMQ::Util.resultcode_ok?(rc)
+    raise "ZMQ Error: #{ZMQ::Util.error_string}"
+  end
+end
+
+if ARGV.length != 1
+  print "usage: watchdog <notifier-host>\n"
+  exit 1
+end
+
+notifier_ep = "tcp://#{ARGV[0]}:7770"
+control_ep = "tcp://*:7772"
+
+ctx = ZMQ::Context.new()
+notifier_sock = ctx.socket(ZMQ::PUB)
+rc = notifier_sock.connect(notifier_ep)
+raise_if_error(rc)
+
+control_sock = ctx.socket(ZMQ::PULL)
+rc = control_sock.bind(control_ep)
+raise_if_error(rc)
+
+poller = ZMQ::Poller.new
+poller.register_readable(control_sock)
+
+children = {}
+
+#  Delete process if it went away
+trap("CHLD") do
+  pid = Process.wait
+  children.each do |k, v|
+    if v[:pid] == pid
+      children.delete(k)
+    end
+  end
+end
+
+#  Kill any children on exit
+trap("TERM") do
+  children.each do |k, v|
+    Process.kill("KILL", v[:pid])
+  end
+end
+
+#
+#  Main loop
+#
+loop do
+  ready = poller.poll(1)
+
+  #  Process commands, if any.
+  if (ready == 1 && poller.readables.include?(control_sock))
+    msg = ''
+    rc = control_sock.recv_string(msg)
+    raise_if_error(rc)
+    if (msg =~ /^START (.+)$/)
+      command = $1
+      key = command.split()[0]
+      unless children.has_key?(key)
+        exec_command = "./" + key
+        if File.exists?(exec_command) && File.executable?(exec_command)
+          children[key] = {}
+          children[key][:pid] = Process.spawn("./" + command)
+          children[key][:command] = command
+        end
+      end
+    elsif (msg =~ /^STOP (.+)$/)
+      command = $1
+      key = command.split()[0]
+      if children.has_key?(key)
+        Process.kill("KILL", children[key][:pid])
+        while children.has_key?(key)
+          # nothing  
+        end
+      end
+    end
+  #  Otherwise, send out status messages to notifier.
+  else
+    status = "WATCHDOG ALIVE " + Socket.gethostname + " " + Time.now.to_f.to_s
+    rc = notifier_sock.send_string(status)
+    raise_if_error(rc)
+    children.each do |k, v|
+      status = "WATCHDOG RUNNING " + Socket.gethostname + \
+        " " + Time.now.to_f.to_s + " " + v[:command]
+      rc = notifier_sock.send_string(status)
+      raise_if_error(rc)
+    end
+  end
+end
+