pmdalibvirt: add support for metric labels

First attempt to add labels support for pmdalibirt:

* metric_source is either host or guest depending on whether the
  metric is hypervisor or VM related
* guest_name is the VM name as specified in the domain XML

Relates: #1847

src/pmdas/libvirt/pmdalibvirt.python

@@ -42,7 +42,7 @@ from ctypes import c_int
 from pcp.pmapi import pmUnits
 from pcp.pmapi import pmContext as PCP
 from pcp.pmda import PMDA, pmdaIndom, pmdaMetric
-from cpmapi import PM_INDOM_NULL
+from cpmapi import PM_INDOM_NULL, PM_LABEL_ITEM
 from cpmapi import PM_TYPE_U32, PM_TYPE_U64, PM_TYPE_STRING
 from cpmapi import PM_SEM_COUNTER, PM_SEM_INSTANT, PM_SEM_DISCRETE
 from cpmapi import PM_COUNT_ONE, PM_SPACE_BYTE, PM_SPACE_KBYTE, PM_TIME_SEC, PM_TIME_NSEC
@@ -68,6 +68,7 @@ class LibvirtPMDA(PMDA):
         self.set_user(self.user)
 
         self.doms = []
+        self.vm_names = {}
         self.connect_pmcd()
         self.conn = self.connect_libvirt()
 
@@ -367,6 +368,8 @@ class LibvirtPMDA(PMDA):
 
         self.set_refresh(self.libvirt_refresh)
         self.set_fetch_callback(self.libvirt_fetch_callback)
+        self.set_label(self.libvirt_label)
+        self.set_label_callback(self.libvirt_label_callback)
 
         @atexit.register
         def cleanup(): # pylint: disable=unused-variable
@@ -410,6 +413,8 @@ class LibvirtPMDA(PMDA):
         try:
             conn = libvirt.openReadOnly(self.uri)
             self.doms = conn.listAllDomains(libvirt.VIR_CONNECT_LIST_DOMAINS_ACTIVE)
+            for dom in self.doms:
+                self.vm_names[dom.UUIDString()] = dom.name()
             if not os.environ.get('PCP_PYTHON_DOMAIN') and not os.environ.get('PCP_PYTHON_PMNS'):
                 self.log("Connected as " + self.user + " to " + self.uri + ".")
         except libvirt.libvirtError as error:
@@ -460,6 +465,7 @@ class LibvirtPMDA(PMDA):
             self.conn = self.connect_libvirt()
             if not self.conn:
                 self.doms = []
+                self.vm_names = {}
                 self.replace_indom(self.vm_indom, {"0":c_int(1)})
                 self.replace_indom(self.vm_vcpu_indom, {"0":c_int(1)})
                 self.replace_indom(self.vm_block_indom, {"0":c_int(1)})
@@ -472,10 +478,13 @@ class LibvirtPMDA(PMDA):
         if cluster == self.vm_cluster:
             try:
                 self.doms = self.conn.listAllDomains(libvirt.VIR_CONNECT_LIST_DOMAINS_ACTIVE)
+                for dom in self.doms:
+                    self.vm_names[dom.UUIDString()] = dom.name()
             except libvirt.libvirtError as error:
                 self.log("Failed to list domains: %s" % error)
                 self.conn = None
                 self.doms = []
+                self.vm_names = {}
                 return
             insts = {}
             for dom in self.doms:
@@ -770,5 +779,19 @@ class LibvirtPMDA(PMDA):
 
         return [PM_ERR_PMID, 0]
 
+    def libvirt_label(self, ident, label_type):
+        """Cluster and instance domain labels"""
+        if label_type == PM_LABEL_ITEM:
+            cluster = self.pmid_cluster(ident)
+            if cluster == self.hv_cluster:
+                return '{"metric_source":"host"}'
+            return '{"metric_source":"guest"}'
+        return '{}'
+
+    def libvirt_label_callback(self, indom, inst):
+        """Instance labels"""
+        name = self.vm_names[self.inst_name_lookup(indom, inst).split('::')[0]]
+        return '{"guest_name":"' + name + '"}'
+
 if __name__ == '__main__':
     LibvirtPMDA('libvirt', 140).run()