Reputation: 10249
I have the following python boto3 code with a potentially infinite while-loop
. Generally, after a few minutes the while-loop
succeeds. However, if something fails on the AWS side the program could hang for an indefinite period.
I am sure that this is not the most appropriate way to do this.
# credentials stored in ../.aws/credentials
# region stored in ../.aws/config
# builtins
from time import sleep
# plugins
import boto3
# Assign server instance IDs.
cye_production_web_server_2 = 'i-FAKE-ID'
# Setup EC2 client
ec2 = boto3.client('ec2')
# Start the second web server.
start_response = ec2.start_instances(
InstanceIds=[cye_production_web_server_2, ],
DryRun=False
)
print(
'instance id:',
start_response['StartingInstances'][0]['InstanceId'],
'is',
start_response['StartingInstances'][0]['CurrentState']['Name']
)
# Wait until status is 'ok'
status = None
while status != 'ok':
status_response = ec2.describe_instance_status(
DryRun=False,
InstanceIds=[cye_production_web_server_2, ],
)
status = status_response['InstanceStatuses'][0]['SystemStatus']['Status']
sleep(5) # 5 second throttle
print(status_response)
print('status is', status.capitalize())
Upvotes: 0
Views: 1752
Reputation: 11
Use timeout might be a better idea
import time
systemstatus = False
timeout = time.time() + 60*minute
while systemstatus is not True:
status = ec2.describe_instance_status( \
DryRun = False,
InstanceIds = [instance_id]
)
if status['InstanceStatuses'][0]['SystemStatus']['Status'] == 'ok':
systemstatus = True
if time.time() > timeout:
break
else:
time.sleep(10)
Upvotes: 0
Reputation: 34327
Implement a counter in the loop and fail after so many attempts
status = None
counter = 5
while (status != 'ok' and counter > 0):
status_response = ec2.describe_instance_status(
DryRun=False,
InstanceIds=[cye_production_web_server_2, ],
)
status = status_response['InstanceStatuses'][0]['SystemStatus']['Status']
sleep(5) # 5 second throttle
counter=counter-1
print(status_response)
print('status is', status.capitalize())
Upvotes: 3
Reputation: 4728
You could try doing it in a for
loop instead with a fixed number of tries.
For example:
MAX_RETRIES = 5
# Try until status is 'ok'
for x in range(MAX_RETRIES):
status_response = ec2.describe_instance_status(
DryRun=False,
InstanceIds=[cye_production_web_server_2, ],
)
status = status_response['InstanceStatuses'][0]['SystemStatus']['Status']
if status != 'ok':
sleep(5) # 5 second throttle
else:
break
Upvotes: 0