Running into rate limit for Boto3 EC2 create_snapshots - aws-lambda

Question

I ran the code at the bottom of this post in my environment and got the following error after a few successes:
An error occurred (SnapshotCreationPerVolumeRateExceeded) when calling the CreateSnapshot operation: The maximum per volume CreateSnapshot request rate has been exceeded. Use an increasing or variable sleep interval between requests.
I'm used to doing something like this to paginate my results using a MaxResults variable and the NextToken returned by the response:
maxResults = 100
result = ec2.describe_instances(MaxResults=maxResults)
nextToken = result['NextToken']
instance_ids = []
for reservation in result['Reservations']:
for instances in reservation['Instances']:
for i in instances:
instance_ids.append(i['InstanceId'])
size = len(instance_ids)
while size == maxResults:
result = ec2.describe_instances(MaxResults=maxResults, NextToken=nextToken)
nextToken = result['NextToken']
size = len(instance_ids)
# etc...
However, because I'm already filtering by tag in my describe_instances call, I'm not allowed to pass a maxResults parameter as well. Additionally, create_snapshot's call signature only allows me to specify a dry run, the volume ID, and a description of the snapshot, and does not return a nextToken or similar. How can I avoid this error - must I introduce a sleep like the error message suggests?
Lambda function code:
from __future__ import print_function
import boto3
import datetime
import time
ec2 = boto3.client('ec2')
def createScheduleSnapshots(event, context):
errors = []
try:
print("Creating snapshots on " + str(datetime.datetime.today()) + ".")
schedulers = ec2.describe_instances(Filters=[{'Name':'tag:GL-sub-purpose', 'Values':['Schedule']}])
schedule_instances = []
for reservation in schedulers['Reservations']:
for instance in reservation['Instances']:
schedule_instances.append(instance)
print("Performing backup on " + str(len(schedule_instances)) + " schedules.")
successful = []
failed = []
for s in schedule_instances:
try:
instanceId=s['InstanceId']
blockDeviceMappings = s['BlockDeviceMappings']
snapshotDescription = instanceId + "-" + str(datetime.date.today().strftime('%Y-%m-%d')) + "-46130e7ac954-automated"
for bd_maps in blockDeviceMappings:
if (bd_maps['DeviceName'] == '/dev/sdf'): #Don't back up OS
volumeId = bd_maps['Ebs']['VolumeId']
print("\tSnapshotting " + instanceId)
ec2.create_snapshot(
VolumeId=volumeId,
Description=snapshotDescription
)
successful.append(instanceId)
except Exception as e:
print(e)
errors.append(e)
failed.append(instanceId + " :\t" + str(e))
print("Performed backup on " + str(len(successful)) + " schedulers. Failed backup on " + str(len(failed)) + " schedulers. ")
except Exception as e:
print(e)
errors.append(e)
if len(errors) == 0:
return "Success"
else:
raise Exception("Errors during invocation of Lambda. " + str(errors))