python: Break unixctl implementation into registry, client, and server.

I wish to add some unixctl commands to the Python vlog module.  However,
importing ovs.unixctl in ovs.vlog creates a circular dependency, because
ovs.unixctl imports ovs.vlog already.  The solution, in this commit, is to
break the unixctl module into three parts: a register (ovs.unixctl) that
does not depend on ovs.vlog, and client (ovs.unixctl.client) and server
(ovs.unixctl.server) modules that do.  This breaks the circular dependency.

Signed-off-by: Ben Pfaff <blp@nicira.com>

python/automake.mk

@@ -27,7 +27,9 @@ ovs_pyfiles = \
 	python/ovs/socket_util.py \
 	python/ovs/stream.py \
 	python/ovs/timeval.py \
-	python/ovs/unixctl.py \
+	python/ovs/unixctl/__init__.py \
+	python/ovs/unixctl/client.py \
+	python/ovs/unixctl/server.py \
 	python/ovs/util.py \
 	python/ovs/version.py \
 	python/ovs/vlog.py

python/ovs/unixctl/__init__.py

@@ -0,0 +1,83 @@
+# Copyright (c) 2011, 2012 Nicira, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at:
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import types
+
+import ovs.util
+
+commands = {}
+strtypes = types.StringTypes
+
+
+class _UnixctlCommand(object):
+    def __init__(self, usage, min_args, max_args, callback, aux):
+        self.usage = usage
+        self.min_args = min_args
+        self.max_args = max_args
+        self.callback = callback
+        self.aux = aux
+
+
+def _unixctl_help(conn, unused_argv, unused_aux):
+    reply = "The available commands are:\n"
+    command_names = sorted(commands.keys())
+    for name in command_names:
+        reply += "  "
+        usage = commands[name].usage
+        if usage:
+            reply += "%-23s %s" % (name, usage)
+        else:
+            reply += name
+        reply += "\n"
+    conn.reply(reply)
+
+
+def command_register(name, usage, min_args, max_args, callback, aux):
+    """ Registers a command with the given 'name' to be exposed by the
+    UnixctlServer. 'usage' describes the arguments to the command; it is used
+    only for presentation to the user in "help" output.
+
+    'callback' is called when the command is received.  It is passed a
+    UnixctlConnection object, the list of arguments as unicode strings, and
+    'aux'.  Normally 'callback' should reply by calling
+    UnixctlConnection.reply() or UnixctlConnection.reply_error() before it
+    returns, but if the command cannot be handled immediately, then it can
+    defer the reply until later.  A given connection can only process a single
+    request at a time, so a reply must be made eventually to avoid blocking
+    that connection."""
+
+    assert isinstance(name, strtypes)
+    assert isinstance(usage, strtypes)
+    assert isinstance(min_args, int)
+    assert isinstance(max_args, int)
+    assert isinstance(callback, types.FunctionType)
+
+    if name not in commands:
+        commands[name] = _UnixctlCommand(usage, min_args, max_args, callback,
+                                         aux)
+
+def socket_name_from_target(target):
+    assert isinstance(target, strtypes)
+
+    if target.startswith("/"):
+        return 0, target
+
+    pidfile_name = "%s/%s.pid" % (ovs.dirs.RUNDIR, target)
+    pid = ovs.daemon.read_pidfile(pidfile_name)
+    if pid < 0:
+        return -pid, "cannot read pidfile \"%s\"" % pidfile_name
+
+    return 0, "%s/%s.%d.ctl" % (ovs.dirs.RUNDIR, target, pid)
+
+command_register("help", "", 0, 0, _unixctl_help, None)

python/ovs/unixctl/client.py

@@ -0,0 +1,70 @@
+# Copyright (c) 2011, 2012 Nicira, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at:
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import copy
+import errno
+import os
+import types
+
+import ovs.jsonrpc
+import ovs.stream
+import ovs.util
+
+
+vlog = ovs.vlog.Vlog("unixctl_client")
+strtypes = types.StringTypes
+
+
+class UnixctlClient(object):
+    def __init__(self, conn):
+        assert isinstance(conn, ovs.jsonrpc.Connection)
+        self._conn = conn
+
+    def transact(self, command, argv):
+        assert isinstance(command, strtypes)
+        assert isinstance(argv, list)
+        for arg in argv:
+            assert isinstance(arg, strtypes)
+
+        request = ovs.jsonrpc.Message.create_request(command, argv)
+        error, reply = self._conn.transact_block(request)
+
+        if error:
+            vlog.warn("error communicating with %s: %s"
+                      % (self._conn.name, os.strerror(error)))
+            return error, None, None
+
+        if reply.error is not None:
+            return 0, str(reply.error), None
+        else:
+            assert reply.result is not None
+            return 0, None, str(reply.result)
+
+    def close(self):
+        self._conn.close()
+        self.conn = None
+
+    @staticmethod
+    def create(path):
+        assert isinstance(path, str)
+
+        unix = "unix:%s" % ovs.util.abs_file_name(ovs.dirs.RUNDIR, path)
+        error, stream = ovs.stream.Stream.open_block(
+            ovs.stream.Stream.open(unix))
+
+        if error:
+            vlog.warn("failed to connect to %s" % path)
+            return error, None
+
+        return 0, UnixctlClient(ovs.jsonrpc.Connection(stream))

python/ovs/unixctl/server.py

@@ -17,89 +17,19 @@ import errno
 import os
 import types
 
-import ovs.daemon
 import ovs.dirs
 import ovs.jsonrpc
 import ovs.stream
+import ovs.unixctl
 import ovs.util
 import ovs.version
 import ovs.vlog
 
 Message = ovs.jsonrpc.Message
-vlog = ovs.vlog.Vlog("unixctl")
-commands = {}
+vlog = ovs.vlog.Vlog("unixctl_server")
 strtypes = types.StringTypes
 
 
-class _UnixctlCommand(object):
-    def __init__(self, usage, min_args, max_args, callback, aux):
-        self.usage = usage
-        self.min_args = min_args
-        self.max_args = max_args
-        self.callback = callback
-        self.aux = aux
-
-
-def _unixctl_help(conn, unused_argv, unused_aux):
-    assert isinstance(conn, UnixctlConnection)
-    reply = "The available commands are:\n"
-    command_names = sorted(commands.keys())
-    for name in command_names:
-        reply += "  "
-        usage = commands[name].usage
-        if usage:
-            reply += "%-23s %s" % (name, usage)
-        else:
-            reply += name
-        reply += "\n"
-    conn.reply(reply)
-
-
-def _unixctl_version(conn, unused_argv, version):
-    assert isinstance(conn, UnixctlConnection)
-    version = "%s (Open vSwitch) %s" % (ovs.util.PROGRAM_NAME, version)
-    conn.reply(version)
-
-
-def command_register(name, usage, min_args, max_args, callback, aux):
-    """ Registers a command with the given 'name' to be exposed by the
-    UnixctlServer. 'usage' describes the arguments to the command; it is used
-    only for presentation to the user in "help" output.
-
-    'callback' is called when the command is received.  It is passed a
-    UnixctlConnection object, the list of arguments as unicode strings, and
-    'aux'.  Normally 'callback' should reply by calling
-    UnixctlConnection.reply() or UnixctlConnection.reply_error() before it
-    returns, but if the command cannot be handled immediately, then it can
-    defer the reply until later.  A given connection can only process a single
-    request at a time, so a reply must be made eventually to avoid blocking
-    that connection."""
-
-    assert isinstance(name, strtypes)
-    assert isinstance(usage, strtypes)
-    assert isinstance(min_args, int)
-    assert isinstance(max_args, int)
-    assert isinstance(callback, types.FunctionType)
-
-    if name not in commands:
-        commands[name] = _UnixctlCommand(usage, min_args, max_args, callback,
-                                         aux)
-
-
-def socket_name_from_target(target):
-    assert isinstance(target, strtypes)
-
-    if target.startswith("/"):
-        return 0, target
-
-    pidfile_name = "%s/%s.pid" % (ovs.dirs.RUNDIR, target)
-    pid = ovs.daemon.read_pidfile(pidfile_name)
-    if pid < 0:
-        return -pid, "cannot read pidfile \"%s\"" % pidfile_name
-
-    return 0, "%s/%s.%d.ctl" % (ovs.dirs.RUNDIR, target, pid)
-
-
 class UnixctlConnection(object):
     def __init__(self, rpc):
         assert isinstance(rpc, ovs.jsonrpc.Connection)
@@ -177,7 +107,7 @@ class UnixctlConnection(object):
         error = None
         params = request.params
         method = request.method
-        command = commands.get(method)
+        command = ovs.unixctl.commands.get(method)
         if command is None:
             error = '"%s" is not a valid command' % method
         elif len(params) < command.min_args:
@@ -200,6 +130,11 @@ class UnixctlConnection(object):
             self.reply_error(error)
 
 
+def _unixctl_version(conn, unused_argv, version):
+    assert isinstance(conn, UnixctlConnection)
+    version = "%s (Open vSwitch) %s" % (ovs.util.PROGRAM_NAME, version)
+    conn.reply(version)
+
 class UnixctlServer(object):
     def __init__(self, listener):
         assert isinstance(listener, ovs.stream.PassiveStream)
@@ -262,8 +197,8 @@ class UnixctlServer(object):
                                % path)
             return error, None
 
-        command_register("help", "", 0, 0, _unixctl_help, None)
-        command_register("version", "", 0, 0, _unixctl_version, version)
+        ovs.unixctl.command_register("version", "", 0, 0, _unixctl_version,
+                                     version)
 
         return 0, UnixctlServer(listener)