Patchwork [1/2] QMP: add get_events(wait=True) option

login
register
mail settings
Submitter Stefan Hajnoczi
Date May 25, 2011, 6:48 p.m.
Message ID <1306349281-16913-1-git-send-email-stefanha@linux.vnet.ibm.com>
Download mbox | patch
Permalink /patch/97397/
State New
Headers show

Comments

Stefan Hajnoczi - May 25, 2011, 6:48 p.m.
The get_events() function polls for new QMP events and then returns.  It
can be useful to wait for the next QMP event so add the boolean 'wait'
keyword argument.

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 QMP/qmp.py |   11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)
Luiz Capitulino - May 25, 2011, 9:15 p.m.
On Wed, 25 May 2011 19:48:00 +0100
Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> wrote:

> The get_events() function polls for new QMP events and then returns.  It
> can be useful to wait for the next QMP event so add the boolean 'wait'
> keyword argument.
> 
> Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
> ---
>  QMP/qmp.py |   11 ++++++++---
>  1 files changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/QMP/qmp.py b/QMP/qmp.py
> index 14ce8b0..2565508 100644
> --- a/QMP/qmp.py
> +++ b/QMP/qmp.py
> @@ -43,7 +43,7 @@ class QEMUMonitorProtocol:
>              family = socket.AF_UNIX
>          return socket.socket(family, socket.SOCK_STREAM)
>  
> -    def __json_read(self):
> +    def __json_read(self, only_event=False):
>          while True:
>              data = self.__sockfile.readline()
>              if not data:
> @@ -51,7 +51,8 @@ class QEMUMonitorProtocol:
>              resp = json.loads(data)
>              if 'event' in resp:
>                  self.__events.append(resp)
> -                continue
> +                if not only_event:
> +                    continue
>              return resp
>  
>      error = socket.error
> @@ -106,9 +107,11 @@ class QEMUMonitorProtocol:
>              qmp_cmd['id'] = id
>          return self.cmd_obj(qmp_cmd)
>  
> -    def get_events(self):
> +    def get_events(self, wait=False):
>          """
>          Get a list of available QMP events.
> +
> +        @param wait: block until an event is available (bool)
>          """
>          self.__sock.setblocking(0)
>          try:
> @@ -118,6 +121,8 @@ class QEMUMonitorProtocol:
>                  # No data available
>                  pass
>          self.__sock.setblocking(1)
> +        if not self.__events and wait:
> +            self.__json_read(only_event=True)
>          return self.__events

Maybe this is better (untested):

    def get_events(self, wait=False):
        """
        Get a list of available QMP events.

        @param wait: block until an event is available (bool)
        """
        if not wait:
            self.__sock.setblocking(0)
        try:
            self.__json_read(only_event=wait)
        except socket.error, err:
            if err[0] == errno.EAGAIN:
                # No data available
                pass
        if not wait:
            self.__sock.setblocking(1)
        return self.__events

>  
>      def clear_events(self):
Stefan Hajnoczi - May 26, 2011, 8:03 a.m.
On Wed, May 25, 2011 at 10:15 PM, Luiz Capitulino
<lcapitulino@redhat.com> wrote:
> On Wed, 25 May 2011 19:48:00 +0100
> Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> wrote:
>
>> The get_events() function polls for new QMP events and then returns.  It
>> can be useful to wait for the next QMP event so add the boolean 'wait'
>> keyword argument.
>>
>> Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
>> ---
>>  QMP/qmp.py |   11 ++++++++---
>>  1 files changed, 8 insertions(+), 3 deletions(-)
>>
>> diff --git a/QMP/qmp.py b/QMP/qmp.py
>> index 14ce8b0..2565508 100644
>> --- a/QMP/qmp.py
>> +++ b/QMP/qmp.py
>> @@ -43,7 +43,7 @@ class QEMUMonitorProtocol:
>>              family = socket.AF_UNIX
>>          return socket.socket(family, socket.SOCK_STREAM)
>>
>> -    def __json_read(self):
>> +    def __json_read(self, only_event=False):
>>          while True:
>>              data = self.__sockfile.readline()
>>              if not data:
>> @@ -51,7 +51,8 @@ class QEMUMonitorProtocol:
>>              resp = json.loads(data)
>>              if 'event' in resp:
>>                  self.__events.append(resp)
>> -                continue
>> +                if not only_event:
>> +                    continue
>>              return resp
>>
>>      error = socket.error
>> @@ -106,9 +107,11 @@ class QEMUMonitorProtocol:
>>              qmp_cmd['id'] = id
>>          return self.cmd_obj(qmp_cmd)
>>
>> -    def get_events(self):
>> +    def get_events(self, wait=False):
>>          """
>>          Get a list of available QMP events.
>> +
>> +        @param wait: block until an event is available (bool)
>>          """
>>          self.__sock.setblocking(0)
>>          try:
>> @@ -118,6 +121,8 @@ class QEMUMonitorProtocol:
>>                  # No data available
>>                  pass
>>          self.__sock.setblocking(1)
>> +        if not self.__events and wait:
>> +            self.__json_read(only_event=True)
>>          return self.__events
>
> Maybe this is better (untested):

I've tested it because that's how I implemented it first too :).
However, I don't want to block until the QMP monitor sends the next
event when there is already a received event pending.

The patch I posted polls for new events first, then only blocks if
there are no events available.

Stefan
Luiz Capitulino - May 26, 2011, 12:47 p.m.
On Thu, 26 May 2011 09:03:49 +0100
Stefan Hajnoczi <stefanha@gmail.com> wrote:

> On Wed, May 25, 2011 at 10:15 PM, Luiz Capitulino
> <lcapitulino@redhat.com> wrote:
> > On Wed, 25 May 2011 19:48:00 +0100
> > Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> wrote:
> >
> >> The get_events() function polls for new QMP events and then returns.  It
> >> can be useful to wait for the next QMP event so add the boolean 'wait'
> >> keyword argument.
> >>
> >> Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
> >> ---
> >>  QMP/qmp.py |   11 ++++++++---
> >>  1 files changed, 8 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/QMP/qmp.py b/QMP/qmp.py
> >> index 14ce8b0..2565508 100644
> >> --- a/QMP/qmp.py
> >> +++ b/QMP/qmp.py
> >> @@ -43,7 +43,7 @@ class QEMUMonitorProtocol:
> >>              family = socket.AF_UNIX
> >>          return socket.socket(family, socket.SOCK_STREAM)
> >>
> >> -    def __json_read(self):
> >> +    def __json_read(self, only_event=False):
> >>          while True:
> >>              data = self.__sockfile.readline()
> >>              if not data:
> >> @@ -51,7 +51,8 @@ class QEMUMonitorProtocol:
> >>              resp = json.loads(data)
> >>              if 'event' in resp:
> >>                  self.__events.append(resp)
> >> -                continue
> >> +                if not only_event:
> >> +                    continue
> >>              return resp
> >>
> >>      error = socket.error
> >> @@ -106,9 +107,11 @@ class QEMUMonitorProtocol:
> >>              qmp_cmd['id'] = id
> >>          return self.cmd_obj(qmp_cmd)
> >>
> >> -    def get_events(self):
> >> +    def get_events(self, wait=False):
> >>          """
> >>          Get a list of available QMP events.
> >> +
> >> +        @param wait: block until an event is available (bool)
> >>          """
> >>          self.__sock.setblocking(0)
> >>          try:
> >> @@ -118,6 +121,8 @@ class QEMUMonitorProtocol:
> >>                  # No data available
> >>                  pass
> >>          self.__sock.setblocking(1)
> >> +        if not self.__events and wait:
> >> +            self.__json_read(only_event=True)
> >>          return self.__events
> >
> > Maybe this is better (untested):
> 
> I've tested it because that's how I implemented it first too :).
> However, I don't want to block until the QMP monitor sends the next
> event when there is already a received event pending.
> 
> The patch I posted polls for new events first, then only blocks if
> there are no events available.

Ok, pushed both patches to the QMP queue.

Thanks.

Patch

diff --git a/QMP/qmp.py b/QMP/qmp.py
index 14ce8b0..2565508 100644
--- a/QMP/qmp.py
+++ b/QMP/qmp.py
@@ -43,7 +43,7 @@  class QEMUMonitorProtocol:
             family = socket.AF_UNIX
         return socket.socket(family, socket.SOCK_STREAM)
 
-    def __json_read(self):
+    def __json_read(self, only_event=False):
         while True:
             data = self.__sockfile.readline()
             if not data:
@@ -51,7 +51,8 @@  class QEMUMonitorProtocol:
             resp = json.loads(data)
             if 'event' in resp:
                 self.__events.append(resp)
-                continue
+                if not only_event:
+                    continue
             return resp
 
     error = socket.error
@@ -106,9 +107,11 @@  class QEMUMonitorProtocol:
             qmp_cmd['id'] = id
         return self.cmd_obj(qmp_cmd)
 
-    def get_events(self):
+    def get_events(self, wait=False):
         """
         Get a list of available QMP events.
+
+        @param wait: block until an event is available (bool)
         """
         self.__sock.setblocking(0)
         try:
@@ -118,6 +121,8 @@  class QEMUMonitorProtocol:
                 # No data available
                 pass
         self.__sock.setblocking(1)
+        if not self.__events and wait:
+            self.__json_read(only_event=True)
         return self.__events
 
     def clear_events(self):