Remove "agent_last_heartbeat" internal field from agent drivers

"agent_last_heartbeat" in the driver_internal_info dict of agent drivers is not
used anywhere by ironic itself, except for logging purposes. This
removes it.

Change-Id: Ic198f6a952ed135099bcc525ef548a4aea005056
Closes-Bug: 1602410

doc/source/dev/code-contribution-guide.rst

@@ -201,7 +201,6 @@ Common attributes:
 
 Agent driver attributes:
   * ``agent_url``: A String value of IPA API URL so that Ironic can talk to IPA ramdisk.
-  * ``agent_last_heartbeat``: An Integer value of the last agent heartbeat time.
   * ``hardware_manager_version``: A String value of the version of the hardware manager in IPA ramdisk.
   * ``target_raid_config``: A Dictionary containing the target RAID configuration. This is a copy of
     the same name attribute in Node object. But this one is never actually saved into DB and is only

ironic/drivers/modules/agent_base_vendor.py

@@ -17,7 +17,6 @@
 #    under the License.
 
 import collections
-import time
 
 from ironic_lib import metrics_utils
 from oslo_log import log
@@ -452,11 +451,7 @@ class AgentDeployMixin(object):
 
         node = task.node
         driver_internal_info = node.driver_internal_info
-        LOG.debug(
-            'Heartbeat from %(node)s, last heartbeat at %(heartbeat)s.',
-            {'node': node.uuid,
-             'heartbeat': driver_internal_info.get('agent_last_heartbeat')})
-        driver_internal_info['agent_last_heartbeat'] = int(time.time())
+        LOG.debug('Heartbeat from node %s' % node.uuid)
         driver_internal_info['agent_url'] = callback_url
 
         node.driver_internal_info = driver_internal_info

releasenotes/notes/remove-agent_last_heartbeat-65a9fe02f20465c5.yaml

@@ -0,0 +1,4 @@
+---
+deprecations:
+  - The ``agent_last_heartbeat`` field of ``driver_internal_info`` has been
+    removed from all agent drivers, since this field was unused by ironic.