server: Rework the server API so process and xmlrpc servers coexist

This changes the way bitbake server works quite radically. Now, the
server is always a process based server with the option of starting
an XMLRPC listener on a specific inferface/port.

Behind the scenes this is done with a "bitbake.sock" file alongside
the bitbake.lock file. If we can obtain the lock, we know we need
to start a server. The server always listens on the socket and UIs
can then connect to this. UIs connect by sending a set of three file
descriptors over the domain socket, one for sending commands, one for
receiving command results and the other for receiving events.

These changes meant we can throw away all the horrid server abstraction
code, the plugable transport option to bitbake and the code becomes
much more readable and debuggable. It also likely removes a ton of
ways you could hang the UI/cooker in weird ways due to all the race
conditions that existed with previous processes.

Changes:

 * The foreground option for bitbake-server was dropped. Just tail
   the log if you really want this, the codepaths were complicated enough
   without adding one for this.
 * BBSERVER="autodetect" was dropped. The server will autostart and
   autoconnect in process mode. You have to specify an xmlrpc server
   address since that can't be autodetected. I can't see a use case
   for autodetect now.
 * The transport/servetype option to bitbake was dropped.
 * A BB_SERVER_TIMEOUT variable is added which allows the server
   to stay resident for a period of time after the last client
   disconnects before unloading. This is used if the -T/--idle-timeout
   option is not passed to bitbake.

This change is invasive and may well introduce new issues however I
believe the codebase is in a much better position for further
development and debugging.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 393 insertions, 203 deletions

diff --git a/lib/bb/server/process.py b/lib/bb/server/process.py
index 48da7fe46..6edb0213a 100644
--- a/lib/bb/server/process.py
+++ b/lib/bb/server/process.py
@@ -22,128 +22,205 @@
 
 import bb
 import bb.event
-import itertools
 import logging
 import multiprocessing
+import threading
+import array
 import os
-import signal
 import sys
 import time
 import select
-from queue import Empty
-from multiprocessing import Event, Process, util, Queue, Pipe, queues, Manager
+import socket
+import subprocess
+import errno
+import bb.server.xmlrpcserver
+from bb import daemonize
+from multiprocessing import queues
 
 logger = logging.getLogger('BitBake')
 
-class ServerCommunicator():
-    def __init__(self, connection, event_handle, server):
-        self.connection = connection
-        self.event_handle = event_handle
-        self.server = server
-
-    def runCommand(self, command):
-        # @todo try/except
-        self.connection.send(command)
-
-        if not self.server.is_alive():
-            raise SystemExit
-
-        while True:
-            # don't let the user ctrl-c while we're waiting for a response
-            try:
-                for idx in range(0,4): # 0, 1, 2, 3
-                    if self.connection.poll(5):
-                        return self.connection.recv()
-                    else:
-                        bb.warn("Timeout while attempting to communicate with bitbake server")
-                bb.fatal("Gave up; Too many tries: timeout while attempting to communicate with bitbake server")
-            except KeyboardInterrupt:
-                pass
-
-    def getEventHandle(self):
-        handle, error = self.runCommand(["getUIHandlerNum"])
-        if error:
-            logger.error("Unable to get UI Handler Number: %s" % error)
-            raise BaseException(error)
+class ProcessTimeout(SystemExit):
+    pass
 
-        return handle
-
-class EventAdapter():
-    """
-    Adapter to wrap our event queue since the caller (bb.event) expects to
-    call a send() method, but our actual queue only has put()
-    """
-    def __init__(self, queue):
-        self.queue = queue
-
-    def send(self, event):
-        try:
-            self.queue.put(event)
-        except Exception as err:
-            print("EventAdapter puked: %s" % str(err))
-
-
-class ProcessServer(Process):
+class ProcessServer(multiprocessing.Process):
     profile_filename = "profile.log"
     profile_processed_filename = "profile.log.processed"
 
-    def __init__(self, command_channel, event_queue, featurelist):
-        self._idlefuns = {}
-        Process.__init__(self)
-        self.command_channel = command_channel
-        self.event_queue = event_queue
-        self.event = EventAdapter(event_queue)
-        self.featurelist = featurelist
+    def __init__(self, lock, sock, sockname):
+        multiprocessing.Process.__init__(self)
+        self.command_channel = False
+        self.command_channel_reply = False
         self.quit = False
         self.heartbeat_seconds = 1 # default, BB_HEARTBEAT_EVENT will be checked once we have a datastore.
         self.next_heartbeat = time.time()
 
-        self.quitin, self.quitout = Pipe()
-        self.event_handle = multiprocessing.Value("i")
+        self.event_handle = None
+        self.haveui = False
+        self.lastui = False
+        self.xmlrpc = False
+
+        self._idlefuns = {}
+
+        self.bitbake_lock = lock
+        self.sock = sock
+        self.sockname = sockname
+
+    def register_idle_function(self, function, data):
+        """Register a function to be called while the server is idle"""
+        assert hasattr(function, '__call__')
+        self._idlefuns[function] = data
 
     def run(self):
-        for event in bb.event.ui_queue:
-            self.event_queue.put(event)
-        self.event_handle.value = bb.event.register_UIHhandler(self, True)
+
+        if self.xmlrpcinterface[0]:
+            self.xmlrpc = bb.server.xmlrpcserver.BitBakeXMLRPCServer(self.xmlrpcinterface, self.cooker, self)
+
+            print("Bitbake XMLRPC server address: %s, server port: %s" % (self.xmlrpc.host, self.xmlrpc.port))
 
         heartbeat_event = self.cooker.data.getVar('BB_HEARTBEAT_EVENT')
         if heartbeat_event:
             try:
                 self.heartbeat_seconds = float(heartbeat_event)
             except:
-                # Throwing an exception here causes bitbake to hang.
-                # Just warn about the invalid setting and continue
                 bb.warn('Ignoring invalid BB_HEARTBEAT_EVENT=%s, must be a float specifying seconds.' % heartbeat_event)
+
+        self.timeout = self.server_timeout or self.cooker.data.getVar('BB_SERVER_TIMEOUT')
+        try:
+            if self.timeout:
+                self.timeout = float(self.timeout)
+        except:
+            bb.warn('Ignoring invalid BB_SERVER_TIMEOUT=%s, must be a float specifying seconds.' % self.timeout)
+
+
+        try:
+            self.bitbake_lock.seek(0)
+            self.bitbake_lock.truncate()
+            if self.xmlrpcinterface[0]:
+                self.bitbake_lock.write("%s %s:%s\n" % (os.getpid(), configuration.interface[0], configuration.interface[1]))
+            else:
+                self.bitbake_lock.write("%s\n" % (os.getpid()))
+            self.bitbake_lock.flush()
+        except:
+            pass
+
         bb.cooker.server_main(self.cooker, self.main)
 
     def main(self):
-        # Ignore SIGINT within the server, as all SIGINT handling is done by
-        # the UI and communicated to us
-        self.quitin.close()
-        signal.signal(signal.SIGINT, signal.SIG_IGN)
         bb.utils.set_process_name("Cooker")
+
+        ready = []
+
+        self.controllersock = False
+        fds = [self.sock]
+        if self.xmlrpc:
+            fds.append(self.xmlrpc)
         while not self.quit:
-            try:
-                if self.command_channel.poll():
-                    command = self.command_channel.recv()
-                    self.runCommand(command)
-                if self.quitout.poll():
-                    self.quitout.recv()
+            if self.command_channel in ready:
+                command = self.command_channel.get()
+                if command[0] == "terminateServer":
                     self.quit = True
-                    try:
-                        self.runCommand(["stateForceShutdown"])
-                    except:
-                        pass
-
-                self.idle_commands(.1, [self.command_channel, self.quitout])
-            except Exception:
-                logger.exception('Running command %s', command)
+                    continue
+                try:
+                    print("Running command %s" % command)
+                    self.command_channel_reply.send(self.cooker.command.runCommand(command))
+                except Exception as e:
+                   logger.exception('Exception in server main event loop running command %s (%s)' % (command, str(e)))
+
+            if self.xmlrpc in ready:
+                self.xmlrpc.handle_requests()
+            if self.sock in ready:
+                self.controllersock, address = self.sock.accept()
+                if self.haveui:
+                    print("Dropping connection attempt as we have a UI %s" % (str(ready)))
+                    self.controllersock.close()
+                else:
+                    print("Accepting %s" % (str(ready)))
+                    fds.append(self.controllersock)
+            if self.controllersock in ready:
+                try:
+                    print("Connecting Client")
+                    ui_fds = recvfds(self.controllersock, 3)
+
+                    # Where to write events to
+                    writer = ConnectionWriter(ui_fds[0])
+                    self.event_handle = bb.event.register_UIHhandler(writer, True)
+                    self.event_writer = writer
+
+                    # Where to read commands from
+                    reader = ConnectionReader(ui_fds[1])
+                    fds.append(reader)
+                    self.command_channel = reader
+
+                    # Where to send command return values to
+                    writer = ConnectionWriter(ui_fds[2])
+                    self.command_channel_reply = writer
+
+                    self.haveui = True
+
+                except EOFError:
+                    print("Disconnecting Client")
+                    fds.remove(self.controllersock)
+                    fds.remove(self.command_channel)
+                    bb.event.unregister_UIHhandler(self.event_handle, True)
+                    self.command_channel_reply.writer.close()
+                    self.event_writer.writer.close()
+                    del self.event_writer
+                    self.controllersock.close()
+                    self.haveui = False
+                    self.lastui = time.time()
+                    self.cooker.clientComplete()
+                    if self.timeout is None:
+                        print("No timeout, exiting.")
+                        self.quit = True
+            if not self.haveui and self.lastui and self.timeout and (self.lastui + self.timeout) < time.time():
+                print("Server timeout, exiting.")
+                self.quit = True
 
-        self.event_queue.close()
-        bb.event.unregister_UIHhandler(self.event_handle.value, True)
-        self.command_channel.close()
-        self.cooker.shutdown(True)
-        self.quitout.close()
+            ready = self.idle_commands(.1, fds)
+
+        print("Exiting")
+        try: 
+            self.cooker.shutdown(True)
+        except:
+            pass
+
+        # Remove the socket file so we don't get any more connections to avoid races
+        os.unlink(self.sockname)
+        self.sock.close()
+
+        # Finally release the lockfile but warn about other processes holding it open
+        lock = self.bitbake_lock
+        lockfile = lock.name
+        lock.close()
+        lock = None
+
+        while not lock:
+            with bb.utils.timeout(3):
+                lock = bb.utils.lockfile(lockfile, shared=False, retry=False, block=True)
+                if not lock:
+                    # Some systems may not have lsof available
+                    procs = None
+                    try:
+                        procs = subprocess.check_output(["lsof", '-w', lockfile], stderr=subprocess.STDOUT)
+                    except OSError as e:
+                        if e.errno != errno.ENOENT:
+                            raise
+                    if procs is None:
+                        # Fall back to fuser if lsof is unavailable
+                        try:
+                            procs = subprocess.check_output(["fuser", '-v', lockfile], stderr=subprocess.STDOUT)
+                        except OSError as e:
+                            if e.errno != errno.ENOENT:
+                                raise
+
+                    msg = "Delaying shutdown due to active processes which appear to be holding bitbake.lock"
+                    if procs:
+                        msg += ":\n%s" % str(procs)
+                    print(msg)
+                    return
+        # We hold the lock so we can remove the file (hide stale pid data)
+        bb.utils.remove(lockfile)
+        bb.utils.unlockfile(lock)
 
     def idle_commands(self, delay, fds=None):
         nextsleep = delay
@@ -189,140 +266,253 @@ class ProcessServer(Process):
             nextsleep = self.next_heartbeat - now
 
         if nextsleep is not None:
+            if self.xmlrpc:
+                nextsleep = self.xmlrpc.get_timeout(nextsleep)
             try:
-                select.select(fds,[],[],nextsleep)
+                return select.select(fds,[],[],nextsleep)[0]
             except InterruptedError:
-                # ignore EINTR error, nextsleep only used for wait
-                # certain time
-                pass
+                # Ignore EINTR
+                return []
+        else:
+            return []
+
+
+class ServerCommunicator():
+    def __init__(self, connection, recv):
+        self.connection = connection
+        self.recv = recv
 
     def runCommand(self, command):
-        """
-        Run a cooker command on the server
-        """
-        self.command_channel.send(self.cooker.command.runCommand(command))
 
-    def stop(self):
-        self.quitin.send("quit")
-        self.quitin.close()
+        self.connection.send(command)
+        while True:
+            # don't let the user ctrl-c while we're waiting for a response
+            try:
+                for idx in range(0,4): # 0, 1, 2, 3
+                    if self.recv.poll(1):
+                        return self.recv.get()
+                    else:
+                        bb.warn("Timeout while attempting to communicate with bitbake server")
+                raise ProcessTimeout("Gave up; Too many tries: timeout while attempting to communicate with bitbake server")
+            except KeyboardInterrupt:
+                pass
+
+    def updateFeatureSet(self, featureset):
+        _, error = self.runCommand(["setFeatures", featureset])
+        if error:
+            logger.error("Unable to set the cooker to the correct featureset: %s" % error)
+            raise BaseException(error)
+
+    def getEventHandle(self):
+        handle, error = self.runCommand(["getUIHandlerNum"])
+        if error:
+            logger.error("Unable to get UI Handler Number: %s" % error)
+            raise BaseException(error)
 
-    def addcooker(self, cooker):
-        self.cooker = cooker
+        return handle
 
-    def register_idle_function(self, function, data):
-        """Register a function to be called while the server is idle"""
-        assert hasattr(function, '__call__')
-        self._idlefuns[function] = data
+    def terminateServer(self):
+        self.connection.send(['terminateServer'])
+        return
 
 class BitBakeProcessServerConnection(object):
-    def __init__(self, serverImpl, ui_channel, event_queue):
-        self.procserver = serverImpl
-        self.ui_channel = ui_channel
-        self.event_queue = event_queue
-        self.connection = ServerCommunicator(self.ui_channel, self.procserver.event_handle, self.procserver)
-        self.events = self.event_queue
-        self.terminated = False
-
-    def sigterm_terminate(self):
-        bb.error("UI received SIGTERM")
-        self.terminate()
+    def __init__(self, ui_channel, recv, eq):
+        self.connection = ServerCommunicator(ui_channel, recv)
+        self.events = eq
 
     def terminate(self):
-        if self.terminated:
-            return
-        self.terminated = True
-        def flushevents():
-            while True:
-                try:
-                    event = self.event_queue.get(block=False)
-                except (Empty, IOError):
-                    break
-                if isinstance(event, logging.LogRecord):
-                    logger.handle(event)
-
-        self.procserver.stop()
-
-        while self.procserver.is_alive():
-            flushevents()
-            self.procserver.join(0.1)
-
-        self.ui_channel.close()
-        self.event_queue.close()
-        self.event_queue.setexit()
-        # XXX: Call explicity close in _writer to avoid
-        # fd leakage because isn't called on Queue.close()
-        self.event_queue._writer.close()
-
-    def setupEventQueue(self):
-        pass
-
-# Wrap Queue to provide API which isn't server implementation specific
-class ProcessEventQueue(multiprocessing.queues.Queue):
-    def __init__(self, maxsize):
-        multiprocessing.queues.Queue.__init__(self, maxsize, ctx=multiprocessing.get_context())
-        self.exit = False
-        bb.utils.set_process_name("ProcessEQueue")
-
-    def setexit(self):
-        self.exit = True
-
-    def waitEvent(self, timeout):
-        if self.exit:
-            return self.getEvent()
+        self.socket_connection.close()
+        return
+
+class BitBakeServer(object):
+    def __init__(self, lock, sockname, configuration, featureset):
+
+        self.configuration = configuration
+        self.featureset = featureset
+        self.sockname = sockname
+        self.bitbake_lock = lock
+
+        # Create server control socket
+        if os.path.exists(sockname):
+            os.unlink(sockname)
+
+        self.sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+        # AF_UNIX has path length issues so chdir here to workaround
+        cwd = os.getcwd()
         try:
-            if not self.server.is_alive():
-                return self.getEvent()
-            if timeout == 0:
-                return self.get(False)
-            return self.get(True, timeout)
-        except Empty:
-            return None
+            os.chdir(os.path.dirname(sockname))
+            self.sock.bind(os.path.basename(sockname))
+        finally:
+            os.chdir(cwd)
+        self.sock.listen(1)
+
+        os.set_inheritable(self.sock.fileno(), True)
+        bb.daemonize.createDaemon(self._startServer, "bitbake-cookerdaemon.log")
+        self.sock.close()
+        self.bitbake_lock.close()
+
+    def _startServer(self):
+        server = ProcessServer(self.bitbake_lock, self.sock, self.sockname)
+        self.configuration.setServerRegIdleCallback(server.register_idle_function)
+
+        # Copy prefile and postfile to _server variants
+        for param in ('prefile', 'postfile'):
+            value = getattr(self.configuration, param)
+            if value:
+                setattr(self.configuration, "%s_server" % param, value)
+
+        self.cooker = bb.cooker.BBCooker(self.configuration, self.featureset)
+        server.cooker = self.cooker
+        server.server_timeout = self.configuration.server_timeout
+        server.xmlrpcinterface = self.configuration.xmlrpcinterface
+        print("Started bitbake server pid %d" % os.getpid())
+        server.start()
+
+def connectProcessServer(sockname, featureset):
+    # Connect to socket
+    sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+    # AF_UNIX has path length issues so chdir here to workaround
+    cwd = os.getcwd()
+
+    try:
+        os.chdir(os.path.dirname(sockname))
+        sock.connect(os.path.basename(sockname))
+    finally:
+        os.chdir(cwd)
+
+    try:
+        # Send an fd for the remote to write events to
+        readfd, writefd = os.pipe()
+        eq = BBUIEventQueue(readfd)
+        # Send an fd for the remote to recieve commands from
+        readfd1, writefd1 = os.pipe()
+        command_chan = ConnectionWriter(writefd1)
+        # Send an fd for the remote to write commands results to
+        readfd2, writefd2 = os.pipe()
+        command_chan_recv = ConnectionReader(readfd2)
+
+        sendfds(sock, [writefd, readfd1, writefd2])
+
+        server_connection = BitBakeProcessServerConnection(command_chan, command_chan_recv, eq)
+
+        server_connection.connection.updateFeatureSet(featureset)
+
+        # Save sock so it doesn't get gc'd for the life of our connection
+        server_connection.socket_connection = sock
+    except:
+        sock.close()
+        raise
+
+    return server_connection
+
+def sendfds(sock, fds):
+        '''Send an array of fds over an AF_UNIX socket.'''
+        fds = array.array('i', fds)
+        msg = bytes([len(fds) % 256])
+        sock.sendmsg([msg], [(socket.SOL_SOCKET, socket.SCM_RIGHTS, fds)])
+
+def recvfds(sock, size):
+        '''Receive an array of fds over an AF_UNIX socket.'''
+        a = array.array('i')
+        bytes_size = a.itemsize * size
+        msg, ancdata, flags, addr = sock.recvmsg(1, socket.CMSG_LEN(bytes_size))
+        if not msg and not ancdata:
+            raise EOFError
+        try:
+            if len(ancdata) != 1:
+                raise RuntimeError('received %d items of ancdata' %
+                                   len(ancdata))
+            cmsg_level, cmsg_type, cmsg_data = ancdata[0]
+            if (cmsg_level == socket.SOL_SOCKET and
+                cmsg_type == socket.SCM_RIGHTS):
+                if len(cmsg_data) % a.itemsize != 0:
+                    raise ValueError
+                a.frombytes(cmsg_data)
+                assert len(a) % 256 == msg[0]
+                return list(a)
+        except (ValueError, IndexError):
+            pass
+        raise RuntimeError('Invalid data received')
+
+class BBUIEventQueue:
+    def __init__(self, readfd):
+
+        self.eventQueue = []
+        self.eventQueueLock = threading.Lock()
+        self.eventQueueNotify = threading.Event()
+
+        self.reader = ConnectionReader(readfd)
+
+        self.t = threading.Thread()
+        self.t.setDaemon(True)
+        self.t.run = self.startCallbackHandler
+        self.t.start()
 
     def getEvent(self):
-        try:
-            if not self.server.is_alive():
-                self.setexit()
-            return self.get(False)
-        except Empty:
-            if self.exit:
-                sys.exit(1)
+        self.eventQueueLock.acquire()
+
+        if len(self.eventQueue) == 0:
+            self.eventQueueLock.release()
             return None
 
-class BitBakeServer(object):
-    def initServer(self, single_use=True):
-        # establish communication channels.  We use bidirectional pipes for
-        # ui <--> server command/response pairs
-        # and a queue for server -> ui event notifications
-        #
-        self.ui_channel, self.server_channel = Pipe()
-        self.event_queue = ProcessEventQueue(0)
-        self.serverImpl = ProcessServer(self.server_channel, self.event_queue, None)
-        self.event_queue.server = self.serverImpl
-
-    def detach(self):
-        self.serverImpl.start()
-        return
+        item = self.eventQueue.pop(0)
 
-    def establishConnection(self, featureset):
+        if len(self.eventQueue) == 0:
+            self.eventQueueNotify.clear()
 
-        self.connection = BitBakeProcessServerConnection(self.serverImpl, self.ui_channel, self.event_queue)
+        self.eventQueueLock.release()
+        return item
 
-        _, error = self.connection.connection.runCommand(["setFeatures", featureset])
-        if error:
-            logger.error("Unable to set the cooker to the correct featureset: %s" % error)
-            raise BaseException(error)
-        signal.signal(signal.SIGTERM, lambda i, s: self.connection.sigterm_terminate())
-        return self.connection
+    def waitEvent(self, delay):
+        self.eventQueueNotify.wait(delay)
+        return self.getEvent()
 
-    def addcooker(self, cooker):
-        self.cooker = cooker
-        self.serverImpl.addcooker(cooker)
+    def queue_event(self, event):
+        self.eventQueueLock.acquire()
+        self.eventQueue.append(event)
+        self.eventQueueNotify.set()
+        self.eventQueueLock.release()
 
-    def getServerIdleCB(self):
-        return self.serverImpl.register_idle_function
+    def send_event(self, event):
+        self.queue_event(pickle.loads(event))
 
-    def saveConnectionDetails(self):
-        return
+    def startCallbackHandler(self):
+        bb.utils.set_process_name("UIEventQueue")
+        while True:
+            self.reader.wait()
+            event = self.reader.get()
+            self.queue_event(event)
+
+class ConnectionReader(object):
+
+    def __init__(self, fd):
+        self.reader = multiprocessing.connection.Connection(fd, writable=False)
+        self.rlock = multiprocessing.Lock()
+
+    def wait(self, timeout=None):
+        return multiprocessing.connection.wait([self.reader], timeout)
+
+    def poll(self, timeout=None):
+        return self.reader.poll(timeout)
+
+    def get(self):
+        with self.rlock:
+            res = self.reader.recv_bytes()
+        return multiprocessing.reduction.ForkingPickler.loads(res)
+
+    def fileno(self):
+        return self.reader.fileno()
+
+class ConnectionWriter(object):
+
+    def __init__(self, fd):
+        self.writer = multiprocessing.connection.Connection(fd, readable=False)
+        self.wlock = multiprocessing.Lock()
+        # Why bb.event needs this I have no idea
+        self.event = self
+
+    def send(self, obj):
+        obj = multiprocessing.reduction.ForkingPickler.dumps(obj)
+        with self.wlock:
+            self.writer.send_bytes(obj)
 
-    def endSession(self):
-        self.connection.terminate()