Add command socket support to zuul-merger

Like we have in zuul-executor, add command socket support for
zuul-merger.

Change-Id: I66a2cb2ba3f55bdd03e884f47648278e30d2f6ab
Signed-off-by: Paul Belanger <pabelanger@redhat.com>

doc/source/admin/components.rst

@@ -282,6 +282,11 @@ The following section of ``zuul.conf`` is used by the merger:
 
 .. attr:: merger
 
+   ,, attr:: command_socket
+      :default: /var/lib/zuul/merger.socket
+
+      Path to command socket file for the merger process.
+
    .. attr:: git_dir
 
       Directory in which Zuul should clone git repositories.

zuul/cmd/merger.py

@@ -15,8 +15,12 @@
 # under the License.
 
 import signal
+import socket
+import sys
 
 import zuul.cmd
+import zuul.merger.server
+from zuul.lib.config import get_default
 
 # No zuul imports here because they pull in paramiko which must not be
 # imported until after the daemonization.
@@ -28,14 +32,37 @@ class Merger(zuul.cmd.ZuulDaemonApp):
     app_name = 'merger'
     app_description = 'A standalone Zuul merger.'
 
-    def exit_handler(self, signum, frame):
-        signal.signal(signal.SIGUSR1, signal.SIG_IGN)
+    def createParser(self):
+        parser = super(Merger, self).createParser()
+        parser.add_argument('command',
+                            choices=zuul.merger.server.COMMANDS,
+                            nargs='?')
+        return parser
+
+    def parseArguments(self, args=None):
+        super(Merger, self).parseArguments()
+        if self.args.command:
+            self.args.nodaemon = True
+
+    def send_command(self, cmd):
+        command_socket = get_default(
+            self.config, 'merger', 'command_socket',
+            '/var/lib/zuul/merger.socket')
+        s = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+        s.connect(command_socket)
+        cmd = '%s\n' % cmd
+        s.sendall(cmd.encode('utf8'))
+
+    def exit_handler(self):
         self.merger.stop()
         self.merger.join()
 
     def run(self):
         # See comment at top of file about zuul imports
         import zuul.merger.server
+        if self.args.command in zuul.merger.server.COMMANDS:
+            self.send_command(self.args.command)
+            sys.exit(0)
 
         self.configure_connections(source_only=True)
 
@@ -45,14 +72,18 @@ class Merger(zuul.cmd.ZuulDaemonApp):
                                                      self.connections)
         self.merger.start()
 
-        signal.signal(signal.SIGUSR1, self.exit_handler)
         signal.signal(signal.SIGUSR2, zuul.cmd.stack_dump_handler)
-        while True:
-            try:
-                signal.pause()
-            except KeyboardInterrupt:
-                print("Ctrl + C: asking merger to exit nicely...\n")
-                self.exit_handler(signal.SIGINT, None)
+
+        if self.args.nodaemon:
+            while True:
+                try:
+                    signal.pause()
+                except KeyboardInterrupt:
+                    print("Ctrl + C: asking merger to exit nicely...\n")
+                    self.exit_handler()
+                    sys.exit(0)
+        else:
+            self.merger.join()
 
 
 def main():

zuul/merger/server.py

@@ -19,10 +19,14 @@ import traceback
 
 import gear
 
+from zuul.lib import commandsocket
 from zuul.lib.config import get_default
 from zuul.merger import merger
 
 
+COMMANDS = ['stop']
+
+
 class MergeServer(object):
     log = logging.getLogger("zuul.MergeServer")
 
@@ -40,9 +44,16 @@ class MergeServer(object):
         self.merger = merger.Merger(
             merge_root, connections, merge_email, merge_name, speed_limit,
             speed_time)
+        self.command_map = dict(
+            stop=self.stop)
+        command_socket = get_default(
+            self.config, 'merger', 'command_socket',
+            '/var/lib/zuul/merger.socket')
+        self.command_socket = commandsocket.CommandSocket(command_socket)
 
     def start(self):
         self._running = True
+        self._command_running = True
         server = self.config.get('gearman', 'server')
         port = get_default(self.config, 'gearman', 'port', 4730)
         ssl_key = get_default(self.config, 'gearman', 'ssl_key')
@@ -54,6 +65,13 @@ class MergeServer(object):
         self.worker.waitForServer()
         self.log.debug("Registering")
         self.register()
+        self.log.debug("Starting command processor")
+        self.command_socket.start()
+        self.command_thread = threading.Thread(
+            target=self.runCommand, name='command')
+        self.command_thread.daemon = True
+        self.command_thread.start()
+
         self.log.debug("Starting worker")
         self.thread = threading.Thread(target=self.run)
         self.thread.daemon = True
@@ -67,12 +85,23 @@ class MergeServer(object):
     def stop(self):
         self.log.debug("Stopping")
         self._running = False
+        self._command_running = False
+        self.command_socket.stop()
         self.worker.shutdown()
         self.log.debug("Stopped")
 
     def join(self):
         self.thread.join()
 
+    def runCommand(self):
+        while self._command_running:
+            try:
+                command = self.command_socket.get().decode('utf8')
+                if command != '_stop':
+                    self.command_map[command]()
+            except Exception:
+                self.log.exception("Exception while processing command")
+
     def run(self):
         self.log.debug("Starting merge listener")
         while self._running: