[Working Blog] ONTAP Snapshot Reporting in Python - Part 7 - getSnapshots Function

Using the outputs from part 5, the following function (which we started in part 6) will return all the snapshots for a specified snapshot policy schedule.

import datetime
from datetime import timedelta

### getSnapshots(datetime   ,str   ,int  ,list   ,list ,list,list    ,list)
def getSnapshots(utcdatetime,prefix,count,minutes,hours,days,weekdays,months): 
  ## Variables ##
  xTime     = utcdatetime + datetime.timedelta(minutes=1)
  go        = True
  snapCount = 0
  snapList  = []  
  ## The Go Back In A Minute at a Time Loop ##
  while go:
    match    = False
    xTime    = xTime - timedelta(minutes=1)
    xYear    = xTime.year     
    xMonth   = xTime.month    
    xDay     = xTime.day      
    xWeekDay = xTime.weekday()
    xHour    = xTime.hour     
    xMinute  = xTime.minute # xMin
    ## Checking months ##
    if months != ['X']:
      if xMonth not in set(months):
        xTime = datetime.datetime(xYear,xMonth,1,0,0)
        continue
        # otherwise we might have a match ...	
    ## Checking day/weekday ##
    if days != ['X'] and weekdays != ['X']:
      if xDay not in set(days) or xWeekDay not in set(weekdays):
        xTime  = datetime.datetime(xYear,xMonth,xDay,0,0)	  
        continue
        # otherwise we might have a match ...	
    ## Checking hour ##
    if hours != ['X']:
      if xHour not in set(hours):
        xTime = datetime.datetime(xYear,xMonth,xDay,xHour,0)
        continue
        # otherwise we might have a match ...
    ## Checking minute ##
    if xMinute in set(minutes):
      if hours == ['X'] and days == ['X'] and weekdays == ['X'] and months == ['X']:
        match = True
      elif xHour in set(hours):
        if days == ['X'] and weekdays == ['X'] and months == ['X']:
          match = True
        elif xDay in set(days) or xWeekDay in set(weekdays):
          if months == ['X']:
            match = True
          elif xMonth in set(months):
            match = True
    ##  The snapshot ##
    if match:	
      ## Snap Name at time x (PREFIX.YYYY-MM-DD_HHmm) ##
      xSnapName  = prefix + "."
      xSnapName += str(xYear) + "-"
      xSnapName += "{:02d}".format(xMonth) + "-"
      xSnapName += "{:02d}".format(xDay) + "_"
      xSnapName += "{:02d}".format(xHour)
      xSnapName += "{:02d}".format(xMinute)
      snapList  += [xSnapName]
      snapCount += 1
    ## Count check ##
    if snapCount >= count:
      go = False
  ## Return the list of snaps!
  return snapList

Example usage and output:

Generating All Expected Snapshots for All Snapshot Policies

Okay, so we can construct all the snapshot names from one schedule in a Snapshot Policy. But, snapshot policies can have multiple schedules, so how do we construct all a list of for every schedule in one list!?

This is straightforward, we just loop through the schedules running the function above.

snapPolSnapList = {}

for UUID in snapPolicyUUIDs:
  snapPolSnapList[UUID] = []
  try:
    for s in snapPoliciesByUUID[UUID].copies:
      prefix    = s.prefix
      count     = s.count
      zCronUUID = s.schedule.uuid	
      minutes   = schedByUUID[zCronUUID]['minutes']
      hours     = schedByUUID[zCronUUID]['hours']
      days      = schedByUUID[zCronUUID]['days']
      weekdays  = schedByUUID[zCronUUID]['weekdays']
      months    = schedByUUID[zCronUUID]['months']
      snapPolSnapList[UUID] += getSnapshots(utcDateTime,prefix,count,minutes,hours,days,weekdays,months)
  except AttributeError:
    void = "The snapshot policy has no schedules."

I did notice a problem whilst running this. The default weekly schedule uses Sunday but instead the snapshots had Mondays date. Do we have a difference somewhere of where day 0 is!?

The output of schedByUUID for the weekly cron schedule shows this:

weekly {'minutes': [15], 'hours': [0], 'days': ['X'], 'weekdays': [0], 'months': ['X']}

Sunday is 0. But Python datetime Monday is 0. We'll fix by adding some extra code to modify schedByUUID[UUID]['weekdays'].

## Changing ONTAP day 0 = Sunday, to Python datetime day 0 = Monday ##
for u in schedUUIDs:
  if schedByUUID[u]['weekdays'] != ['X']:
    newWeekdays = []
    for w in schedByUUID[u]['weekdays']:
      x = w - 1
      if x == -1:
        x = 6
      newWeekdays += [x]
    schedByUUID[u]['weekdays'] = newWeekdays

Fixed! I'll add this modification to part 5.

To be continued ...