Python AWS EC2:如何防止实例状态检查的无限循环?
我有以下python boto3代码,其中包含一个潜在的无限Python AWS EC2:如何防止实例状态检查的无限循环?,python,python-3.x,amazon-web-services,amazon-ec2,boto3,Python,Python 3.x,Amazon Web Services,Amazon Ec2,Boto3,我有以下python boto3代码,其中包含一个潜在的无限while循环。通常,几分钟后,while循环成功。然而,如果AWS端出现故障,程序可能会无限期挂起 我相信这不是最恰当的方法 # credentials stored in ../.aws/credentials # region stored in ../.aws/config # builtins from time import sleep # plugins import boto3 # Assign server ins
while循环。通常,几分钟后,while循环
成功。然而,如果AWS端出现故障,程序可能会无限期挂起
我相信这不是最恰当的方法
# 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())
您可以尝试在for
循环中执行,而不是使用固定的尝试次数
例如:
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
您可以尝试在for
循环中执行,而不是使用固定的尝试次数
例如:
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
在循环中实现一个计数器,并在多次尝试后失败
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())
在循环中实现一个计数器,并在多次尝试后失败
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())
使用超时可能是一个更好的主意
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)
使用超时可能是一个更好的主意
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)
5次重试转换为(5秒*5次重试=25秒),我可以增加或减少这个值。在这种情况下,是否有理由不使用while循环。for循环(在本例中似乎更详细)。它更详细一点,这是真的。您可以按照另一个响应者的建议使用while循环,这也会起作用。不使用while循环的原因是为了防止陷入无限循环中,正如您所描述的那样,确定5次重试(5sec*5retries=25秒),我可以增加或减少该值。在这种情况下,是否有理由不使用while循环。for循环(在本例中似乎更详细)。它更详细一点,这是真的。您可以按照另一个响应者的建议使用while循环,这也会起作用。不使用while循环的原因是为了防止陷入您描述的无限循环中