[xcvrd] add support for logging mux_metrics events into state DB (sonic-net#185)

* [xcvrd] add support for logging mux_metrics events into state DB

Description
This PR adds support for logging events for change requests received by xcvrd from swss into state DB.
a typical log would look like this:
1) "xcvrd_switch_standby_start"
2) "2021-05-13 10:01:15.690835"
3) "xcvrd_switch_standby_end"
4) "2021-05-13 10:01:15.696051"

where the key-value pairs signify the type of event requested out of
active/standby/unknown and the timestamp associated with the event.

Motivation and Context
This is required for xcvrd to log the events which it receives in form of requests from swss or any other module into the DB. The timestamp will be useful for debugging the timeline of an event processing from a perspective of other modules as well as xcvrd itself.

How Has This Been Tested?
ran the changes on starlab testbed, by changing the file in the container.

Signed-off-by: vaibhav-dahiya <vdahiya@microsoft.com>

Author: vdahiya12

sonic-xcvrd/xcvrd/xcvrd_utilities/y_cable_helper.py

@@ -3,6 +3,7 @@
     helper utlities configuring y_cable for xcvrd daemon
 """
 
+import datetime
 import threading
 
 from sonic_py_common import daemon_base, logger
@@ -1010,6 +1011,7 @@ def task_worker(self):
         appl_db, state_db, status_tbl, y_cable_tbl = {}, {}, {}, {}
         y_cable_tbl_keys = {}
         mux_cable_command_tbl, y_cable_command_tbl = {}, {}
+        mux_metrics_tbl = {}
 
         sel = swsscommon.Select()
 
@@ -1028,6 +1030,8 @@ def task_worker(self):
             state_db[asic_id] = daemon_base.db_connect("STATE_DB", namespace)
             y_cable_tbl[asic_id] = swsscommon.Table(
                 state_db[asic_id], swsscommon.STATE_HW_MUX_CABLE_TABLE_NAME)
+            mux_metrics_tbl[asic_id] = swsscommon.Table(
+                state_db[asic_id], swsscommon.STATE_MUX_METRICS_TABLE_NAME)
             y_cable_tbl_keys[asic_id] = y_cable_tbl[asic_id].getKeys()
             sel.addSelectable(status_tbl[asic_id])
             sel.addSelectable(mux_cable_command_tbl[asic_id])
@@ -1058,6 +1062,10 @@ def task_worker(self):
                 (port, op, fvp) = status_tbl[asic_index].pop()
                 if not port:
                     break
+
+                # entering this section signifies a start for xcvrd state
+                # change request from swss so initiate recording in mux_metrics table
+                time_start = datetime.datetime.utcnow().strftime("%Y-%b-%d %H:%M:%S.%f")
                 if fvp:
                     # This check might be redundant, to check, the presence of this Port in keys
                     # in logical_port_list but keep for now for coherency
@@ -1091,6 +1099,10 @@ def task_worker(self):
                         y_cable_tbl[asic_index].set(port, fvs_updated)
                         helper_logger.log_info("Got a change event for toggle the mux-direction active side for port {} state from {} to {}".format(
                             port, old_status, new_status))
+                        time_end = datetime.datetime.utcnow().strftime("%Y-%b-%d %H:%M:%S.%f")
+                        fvs_metrics = swsscommon.FieldValuePairs([('xcvrd_switch_{}_start'.format(new_status), str(time_start)),
+                                                                  ('xcvrd_switch_{}_end'.format(new_status), str(time_end))])
+                        mux_metrics_tbl[asic_index].set(port, fvs_metrics)
                     else:
                         helper_logger.log_info("Got a change event on port {} of table {} that does not contain state".format(
                             port, swsscommon.APP_HW_MUX_CABLE_TABLE_NAME))