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Wed, 29 Jan 2020 20:07:19 +0000 (UTC) Received: from localhost.localdomain (ovpn-116-51.gru2.redhat.com [10.97.116.51]) by smtp.corp.redhat.com (Postfix) with ESMTP id 764785DA7B; Wed, 29 Jan 2020 20:07:15 +0000 (UTC) Subject: Re: [PATCH 4/5] python/qemu: qmp: Make QEMUMonitorProtocol a context manager To: John Snow , qemu-devel@nongnu.org References: <20191227134101.244496-1-wainersm@redhat.com> <20191227134101.244496-5-wainersm@redhat.com> From: Wainer dos Santos Moschetta Message-ID: <7ff9fed1-45af-80d7-3214-1d3df86882c4@redhat.com> Date: Wed, 29 Jan 2020 18:07:14 -0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-MC-Unique: 59uGBL_AOb2aItqlCqQwUg-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: ehabkost@redhat.com, crosa@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 1/8/20 10:23 PM, John Snow wrote: > > On 12/27/19 8:41 AM, Wainer dos Santos Moschetta wrote: >> This implement the __enter__ and __exit__ functions on >> QEMUMonitorProtocol class so that it can be used on 'with' >> statement and the resources will be free up on block end: >> >> with QEMUMonitorProtocol(socket_path) as qmp: >> qmp.connect() >> qmp.command('query-status') >> >> Signed-off-by: Wainer dos Santos Moschetta >> --- >> python/qemu/qmp.py | 15 +++++++++++++-- >> 1 file changed, 13 insertions(+), 2 deletions(-) >> >> diff --git a/python/qemu/qmp.py b/python/qemu/qmp.py >> index 914b8c6774..6d55f53595 100644 >> --- a/python/qemu/qmp.py >> +++ b/python/qemu/qmp.py >> @@ -139,6 +139,15 @@ class QEMUMonitorProtocol: >> raise QMPConnectError("Error while reading from socket") >> self.__sock.settimeout(None) >> >> + def __enter__(self): >> + # Implement context manager enter function. >> + return self >> + >> + def __exit__(self, exc_type, exc_value, exc_traceback): >> + # Implement context manager exit function. >> + self.close() >> + return False >> + >> def connect(self, negotiate=True): >> """ >> Connect to the QMP Monitor and perform capabilities negotiation. >> @@ -259,8 +268,10 @@ class QEMUMonitorProtocol: >> """ >> Close the socket and socket file. >> """ >> - self.__sock.close() >> - self.__sockfile.close() >> + if self.__sock: >> + self.__sock.close() >> + if self.__sockfile: >> + self.__sockfile.close() > Not evident on cold read: does self.close() change self.__sock and > self.__sockfile such that they are false-ish? Because self.__exit__() calls self.close() even when a runtime exception raises, there isn't any guarantee that self.__sockfile and self.__sock were initialized. That's the reason why I added those guards. > > close() I suspect might need to actually unset the __sock and __sockfile > fields. The QEMUMonitorProtocol object is designed to be disposed after close() being called. So I don't see any reason to unset those fields. Unless I am missing something here... Thanks for the comments! - Wainer > >> >> def settimeout(self, timeout): >> """ >>