Define public API for receiving guest memory balloon events

When the guest changes its memory balloon applications may want
to know what the new value is, without having to periodically
poll on XML / domain info. Introduce a "balloon change" event
to let apps see this

* include/libvirt/libvirt.h.in: Define the
  virConnectDomainEventBalloonChangeCallback callback
  and VIR_DOMAIN_EVENT_ID_BALLOON_CHANGE constant
* python/libvirt-override-virConnect.py,
  python/libvirt-override.c: Wire up helpers for new event
* daemon/remote.c: Helper for serializing balloon event
* examples/domain-events/events-c/event-test.c,
  examples/domain-events/events-python/event-test.py: Add
  example of balloon event usage
* src/conf/domain_event.c, src/conf/domain_event.h: Handling
  of balloon events
* src/remote/remote_driver.c: Add handler of balloon events
* src/remote/remote_protocol.x: Define wire protocol for
  balloon events
* src/remote_protocol-structs: Likewise.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

2 files changed, 59 insertions, 0 deletions

diff --git a/libvirt-override-virConnect.py b/libvirt-override-virConnect.py
index ecb5680..50177ab 100644
--- a/libvirt-override-virConnect.py
+++ b/libvirt-override-virConnect.py
@@ -161,6 +161,15 @@
         cb(self, virDomain(self, _obj=dom), reason, opaque)
         return 0;
 
+    def _dispatchDomainEventBalloonChangeCallback(self, dom, actual, cbData):
+        """Dispatches events to python user domain balloon change event callbacks
+        """
+        cb = cbData["cb"]
+        opaque = cbData["opaque"]
+
+        cb(self, virDomain(self, _obj=dom), actual, opaque)
+        return 0
+
     def domainEventDeregisterAny(self, callbackID):
         """Removes a Domain Event Callback. De-registering for a
            domain callback will disable delivery of this event type """
diff --git a/libvirt-override.c b/libvirt-override.c
index 8ef9fa0..8b41dff 100644
--- a/libvirt-override.c
+++ b/libvirt-override.c
@@ -5352,6 +5352,53 @@ libvirt_virConnectDomainEventPMSuspendCallback(virConnectPtr conn ATTRIBUTE_UNUS
     return ret;
 }
 
+static int
+libvirt_virConnectDomainEventBalloonChangeCallback(virConnectPtr conn ATTRIBUTE_UNUSED,
+                                                   virDomainPtr dom,
+                                                   unsigned long long actual,
+                                                   void *opaque)
+{
+    PyObject *pyobj_cbData = (PyObject*)opaque;
+    PyObject *pyobj_dom;
+    PyObject *pyobj_ret;
+    PyObject *pyobj_conn;
+    PyObject *dictKey;
+    int ret = -1;
+
+    LIBVIRT_ENSURE_THREAD_STATE;
+
+    /* Create a python instance of this virDomainPtr */
+    virDomainRef(dom);
+    pyobj_dom = libvirt_virDomainPtrWrap(dom);
+    Py_INCREF(pyobj_cbData);
+
+    dictKey = libvirt_constcharPtrWrap("conn");
+    pyobj_conn = PyDict_GetItem(pyobj_cbData, dictKey);
+    Py_DECREF(dictKey);
+
+    /* Call the Callback Dispatcher */
+    pyobj_ret = PyObject_CallMethod(pyobj_conn,
+                                    (char*)"_dispatchDomainEventBalloonChangeCallback",
+                                    (char*)"OLO",
+                                    pyobj_dom,
+                                    (PY_LONG_LONG)actual,
+                                    pyobj_cbData);
+
+    Py_DECREF(pyobj_cbData);
+    Py_DECREF(pyobj_dom);
+
+    if(!pyobj_ret) {
+        DEBUG("%s - ret:%p\n", __FUNCTION__, pyobj_ret);
+        PyErr_Print();
+    } else {
+        Py_DECREF(pyobj_ret);
+        ret = 0;
+    }
+
+    LIBVIRT_RELEASE_THREAD_STATE;
+    return ret;
+}
+
 static PyObject *
 libvirt_virConnectDomainEventRegisterAny(ATTRIBUTE_UNUSED PyObject * self,
                                          PyObject * args)
@@ -5421,6 +5468,9 @@ libvirt_virConnectDomainEventRegisterAny(ATTRIBUTE_UNUSED PyObject * self,
     case VIR_DOMAIN_EVENT_ID_PMSUSPEND:
         cb = VIR_DOMAIN_EVENT_CALLBACK(libvirt_virConnectDomainEventPMSuspendCallback);
         break;
+    case VIR_DOMAIN_EVENT_ID_BALLOON_CHANGE:
+        cb = VIR_DOMAIN_EVENT_CALLBACK(libvirt_virConnectDomainEventBalloonChangeCallback);
+        break;
     }
 
     if (!cb) {