From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1NZNRt-00086n-27 for qemu-devel@nongnu.org; Mon, 25 Jan 2010 06:49:41 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1NZNRn-00086X-7d for qemu-devel@nongnu.org; Mon, 25 Jan 2010 06:49:39 -0500 Received: from [199.232.76.173] (port=46607 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1NZNRn-00086U-1X for qemu-devel@nongnu.org; Mon, 25 Jan 2010 06:49:35 -0500 Received: from mx1.redhat.com ([209.132.183.28]:31493) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1NZNRm-0007vI-JJ for qemu-devel@nongnu.org; Mon, 25 Jan 2010 06:49:34 -0500 Date: Mon, 25 Jan 2010 09:49:16 -0200 From: Luiz Capitulino Subject: Re: [Qemu-devel] [PATCH 08/11] QMP: Asynchronous messages enable/disable support Message-ID: <20100125094916.5d493493@doriath> In-Reply-To: <20100124183514.GA14840@shareable.org> References: <1264108180-3666-1-git-send-email-lcapitulino@redhat.com> <1264108180-3666-9-git-send-email-lcapitulino@redhat.com> <4B59E8DF.5020001@codemonkey.ws> <4B5C2251.7050509@redhat.com> <20100124110725.GA5668@shareable.org> <4B5C68D6.6090502@codemonkey.ws> <20100124183514.GA14840@shareable.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jamie Lokier Cc: qemu-devel@nongnu.org, Avi Kivity , armbru@redhat.com On Sun, 24 Jan 2010 18:35:14 +0000 Jamie Lokier wrote: > Anthony Liguori wrote: > > >I'd like to be able to connect and be sure not to receive any async > > >messages, from simple scripts with simple output parsing. > > > > You can't have simple output parsing with QMP. You need a full JSON > > stack. The simplest script would be a python script that uses the > > builtin json support. Having async messages means that you'll have to > > loop on recv in order make sure that the response is a command response > > vs. an async message. It's just a few lines more of code so I have a > > hard time believing it's really a problem. > > > > But what you probably want is a python QMP library and that would mean > > you wouldn't need the few more lines of code. > > You're right. To be honest, parsing JSON can be done in a single Perl > regexp; a "full JSON stack" isn't much. > > On that note, it'd be good if the end of a QMP message is framed with > something that can't appear inside the JSON value, without having to > parse the JSON incrementally on each partial read(). There are plenty > of short character sequences to choose from that can't appear. Some > JSON parsers expect a whole well-formed expression or throw a parse > error - it's what people do over HTTP after all. So you wait until > you think you've read a whole one, then pass it to the JSON parser. The Monitor sends a CRLF sequence at the end of each line and I have maintained that behaivor for QMP, but it's hard to _guarantee_ that this sequence won't appear inside a json-string. In practice it doesn't, afaik.