API_Statistics.py displays empty headings outside start date and time

[thanh-lam]

Describe the bug
When API_Statistics.py is run with -s or --start date time, like -s "2019-05-03 10:02:30.029198", it also displays empty headings for logs before that date and time. Here, the user only expects to see the logs starting from --start date time.

To Reproduce
Steps to reproduce the behavior:

1. Login to master node, f4n05.
2. Change dir. to /opt/ibm/csm/tools/.
3. Run python ./API_Statistics to see all logs of all dates and times. Copy a date and time from the displayed output.
4. Run python ./API_Statistics -s "2019-05-03 10:02:30.029198" (Or, a recent date and time that exclude older logs).
5. Scroll back to see many of the empty heading.

Expected behavior
When the user run API_Statistics.py with starting date and time, he only expects to see logs for that time period. The script should not display empty headings with no log info.

Screenshots

# python ./API_Statistics.py -s "2019-05-03 10:02:30.029198"
...
+++++++++++++++++++++++++++++++++++++++++++++++++++++Master Log++++++++++++++++++++++++++++++++++++++++++++++++++++
---------------------------------------/var/log/ibm/csm/csm_master.log.old.2---------------------------------------
------------------File Start: 2019-04-30 09:34:58.029334 and File End: 2019-05-02 14:12:55.003402------------------
+++++++++++++++++++++++++++++++++++++++++++++++++++++Master Log++++++++++++++++++++++++++++++++++++++++++++++++++++
Api Function                                       Frequency   Mean      Median    Min       Max       Std     
---------------------------------------/var/log/ibm/csm/csm_master.log.old.3---------------------------------------
Total Calls:  0
Total Errors: 0

Run Time: 0.0182750225067

------------------File Start: 2019-04-26 14:43:38.118020 and File End: 2019-04-30 09:34:58.004686------------------
Api Function                                       Frequency   Mean      Median    Min       Max       Std     
Total Calls:  0
Total Errors: 0

Run Time: 0.0244190692902

Environment (please complete the following information):

• Machine [IST alt. cluster, master node f4n05]
• Version [CSM 1.6.0]

Additional context
The script does display the logs starting from the date and time specified:

+++++++++++++++++++++++++++++++++++++++++++++++++++++Master Log++++++++++++++++++++++++++++++++++++++++++++++++++++
------------------------------------------/var/log/ibm/csm/csm_master.log------------------------------------------
------------------File Start: 2019-05-03 10:02:30.029198 and File End: 2019-05-06 14:30:27.101689------------------
Api Function                                       Frequency   Mean      Median    Min       Max       Std     
csm_allocation_create                                       3  71.560633  64.772258  30.512325  119.397316  36.603251
csm_allocation_delete                                       3  30.297511  30.298023  30.296326  30.298185  0.000841
csm_ib_cable_inventory_collection                           1  0.041657  0.041657  0.041657  0.041657  0.000000
csm_node_attributes_update                                  3  0.018793  0.020028  0.015939  0.020411  0.002024
csm_node_resources_query_all                             7882  0.002392  0.002376  0.001272  0.007249  0.000197
csm_switch_children_inventory_collection                    1  0.016226  0.016226  0.016226  0.016226  0.000000
csm_switch_inventory_collection                             1  0.006728  0.006728  0.006728  0.006728  0.000000
Total Calls:  7894
Total Errors: 0

Run Time: 0.68452000618

Issue Source:
In IST environments, we accumulated lots of old logs so this script may help with showing just the logs we want to see.