static/Reliability/100_Deploy_CloudFormation/Code/Python/server_healthcheck.py [24:288]:
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__author__ = "Seth Eliot"
__email__ = "seliot@amazon.com"
__copyright__ = "Copyright 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved."
__credits__ = ["Seth Eliot", "Adrian Hornsby"]
# html code template for the default page served by this server
html = """
{Title}
{Content}
"""
# RequestHandler: Response depends on type of request made
class RequestHandler(BaseHTTPRequestHandler):
def __init__(self, region, *args, **kwargs):
self.region = region
super().__init__(*args, **kwargs)
def do_GET(self):
print("path: ", self.path)
# Default request URL without additional path info (main response page)
if self.path == '/':
message = "
Enjoy some classic television
"
message += "
What to watch next....
"
# Generate User ID between 1 and 4
# This currently uses a randomly generated user.
# In the future maybe allow student to supply the user ID as input
user_id = str(random.randint(1, 4))
# Error handling:
# surround the call to RecommendationService in a try catch
try:
# Call the getRecommendation API on the RecommendationService
response = call_getRecommendation(self.region, user_id)
# Parses value of recommendation from DynamoDB JSON return value
# {'Item': {
# 'ServiceAPI': {'S': 'getRecommendation'},
# 'UserID': {'N': '1'},
# 'Result': {'S': 'M*A*S*H'}, ...
tv_show = response['Item']['Result']['S']
user_name = response['Item']['UserName']['S']
message += recommendation_message (user_name, tv_show, True)
# Error handling:
# If the service dependency fails, and we cannot make a personalized recommendation
# then give a pre-selected (static) recommendation
# and report diagnostic information
except Exception as e:
message += recommendation_message ('Valued Customer', 'I Love Lucy', False)
message += '
Diagnostic Info:
'
message += ' We are unable to provide personalized recommendations'
message += ' If this persists, please report the following info to us:'
message += str(traceback.format_exception_only(e.__class__, e))
# Add metadata - this is useful in the lab to see
# info about the EC2 instance and Availability Zone
message += get_metadata()
# Send successful response status code
self.send_response(200)
# Send headers
self.send_header('Content-type', 'text/html')
self.end_headers()
# Write html output
self.wfile.write(
bytes(
html.format(Title="Resiliency workshop", Content=message),
"utf-8"
)
)
# Healthcheck request - will be used by the Elastic Load Balancer
elif self.path == '/healthcheck':
is_healthy = False
error_msg = ''
TEST = 'test'
# Make a request to RecommendationService using a predefined
# test call as part of health assessment for this server
try:
# call RecommendationService using the test user
user_id = str(0)
response = call_getRecommendation(self.region, user_id)
# Parses value of recommendation from DynamoDB JSON return value
tv_show = response['Item']['Result']['S']
user_name = response['Item']['UserName']['S']
# Server is healthy of RecommendationService returned the expected response
is_healthy = (tv_show == TEST) and (user_name == TEST)
# If the service dependency fails, capture diagnostic info
except Exception as e:
error_msg += str(traceback.format_exception_only(e.__class__, e))
# Based on the health assessment
# If it succeeded return a healthy code
# If it failed return a server failure code
message = ""
if (is_healthy):
self.send_response(200)
self.send_header('Content-type', 'text/html')
self.end_headers()
message += "
"
message += error_msg
# Add metadata
message += get_metadata()
self.wfile.write(
bytes(
html.format(Title="healthcheck", Content=message),
"utf-8"
)
)
return
# Utility function to consistently format how recommendations are displayed
def recommendation_message (user_name, tv_show, is_custom_reco):
if is_custom_reco:
tag_line = "your recommendation is"
else:
tag_line = "everyone enjoys this classic"
cell1 = "" + user_name + ", " + tag_line + ":"
cell2 = "" + tv_show + ""
reco_msg = "
" + "
" + cell1 + "
" + "
" + cell2 + "
" + "
"
return reco_msg
# Retrieve Metadata which can be useful to students
# For example to see which instance / AWS AZ they are hitting
def get_metadata():
metadata = '
EC2 Metadata
'
try:
message_parts = [
'account_id: %s' % ec2_metadata.account_id,
'ami_id: %s' % ec2_metadata.ami_id,
'availability_zone: %s' % ec2_metadata.availability_zone,
'instance_id: %s' % ec2_metadata.instance_id,
'instance_type: %s' % ec2_metadata.instance_type,
'private_hostname: %s' % ec2_metadata.private_hostname,
'private_ipv4: %s' % ec2_metadata.private_ipv4
]
metadata += ' '.join(message_parts)
except Exception:
metadata += "Running outside AWS"
return metadata
# This method mocks the call to the RecommendationService.
# Calls to the getRecommendation API are actually get_item
# calls to a dynamoDB table
def call_getRecommendation(region, user_id):
# It would be more efficient to create the clients once on init
# But in the lab we change permissions on the EC2 instance
# and this way we are sure to pick up the new credentials
session = boto3.Session()
# Setup client for DDB -- we will use this to mock a service dependency
ddb_client = session.client('dynamodb', region)
# Setup client for SSM -- we use this for parameters used as a
# enable/disable switch in the lab
ssm_client = session.client('ssm', region_name=region)
# Configure if mocked recomendation service is enabled or if it should simulate
# disabled (unreachable)
value = ssm_client.get_parameter(Name='RecommendationServiceEnabled')
dependency_enabled = value['Parameter']['Value'] == "true"
table_name = "RecommendationService" if dependency_enabled else "dependencyShouldFail"
# Call the RecommendationService
# (actually just a simply lookup in a DynamoDB table, which is acting as a mock for the RecommendationService)
response = ddb_client.get_item(
TableName=table_name,
Key={
'ServiceAPI': {
'S': 'getRecommendation',
},
'UserID': {
'N': user_id,
}
}
)
return response
# Initialize server
def run(argv):
try:
opts, args = getopt.getopt(
argv,
"hs:p:r:",
[
"help",
"server_ip=",
"server_port=",
"region="
]
)
except getopt.GetoptError:
print('server.py -s -p -r ')
sys.exit(2)
print(opts)
# Default value - will be over-written if supplied via args
server_port = 80
server_ip = '0.0.0.0'
try:
region = ec2_metadata.region
except:
region = 'us-east-2'
# Get commandline arguments
for opt, arg in opts:
if opt in ("-h", "--help"):
print('server.py -s -p -r ')
sys.exit()
elif opt in ("-s", "--server_ip"):
server_ip = arg
elif opt in ("-p", "--server_port"):
server_port = int(arg)
elif opt in ("-r", "--region"):
region = arg
# start server
print('starting server...')
server_address = (server_ip, server_port)
handler = partial(RequestHandler, region)
httpd = HTTPServer(server_address, handler)
print('running server...')
httpd.serve_forever()
if __name__ == "__main__":
run(sys.argv[1:])
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static/Reliability/300_Health_Checks_and_Dependencies/Code/Python/server_healthcheck.py [24:288]:
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__author__ = "Seth Eliot"
__email__ = "seliot@amazon.com"
__copyright__ = "Copyright 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved."
__credits__ = ["Seth Eliot", "Adrian Hornsby"]
# html code template for the default page served by this server
html = """
{Title}
{Content}
"""
# RequestHandler: Response depends on type of request made
class RequestHandler(BaseHTTPRequestHandler):
def __init__(self, region, *args, **kwargs):
self.region = region
super().__init__(*args, **kwargs)
def do_GET(self):
print("path: ", self.path)
# Default request URL without additional path info (main response page)
if self.path == '/':
message = "
Enjoy some classic television
"
message += "
What to watch next....
"
# Generate User ID between 1 and 4
# This currently uses a randomly generated user.
# In the future maybe allow student to supply the user ID as input
user_id = str(random.randint(1, 4))
# Error handling:
# surround the call to RecommendationService in a try catch
try:
# Call the getRecommendation API on the RecommendationService
response = call_getRecommendation(self.region, user_id)
# Parses value of recommendation from DynamoDB JSON return value
# {'Item': {
# 'ServiceAPI': {'S': 'getRecommendation'},
# 'UserID': {'N': '1'},
# 'Result': {'S': 'M*A*S*H'}, ...
tv_show = response['Item']['Result']['S']
user_name = response['Item']['UserName']['S']
message += recommendation_message (user_name, tv_show, True)
# Error handling:
# If the service dependency fails, and we cannot make a personalized recommendation
# then give a pre-selected (static) recommendation
# and report diagnostic information
except Exception as e:
message += recommendation_message ('Valued Customer', 'I Love Lucy', False)
message += '
Diagnostic Info:
'
message += ' We are unable to provide personalized recommendations'
message += ' If this persists, please report the following info to us:'
message += str(traceback.format_exception_only(e.__class__, e))
# Add metadata - this is useful in the lab to see
# info about the EC2 instance and Availability Zone
message += get_metadata()
# Send successful response status code
self.send_response(200)
# Send headers
self.send_header('Content-type', 'text/html')
self.end_headers()
# Write html output
self.wfile.write(
bytes(
html.format(Title="Resiliency workshop", Content=message),
"utf-8"
)
)
# Healthcheck request - will be used by the Elastic Load Balancer
elif self.path == '/healthcheck':
is_healthy = False
error_msg = ''
TEST = 'test'
# Make a request to RecommendationService using a predefined
# test call as part of health assessment for this server
try:
# call RecommendationService using the test user
user_id = str(0)
response = call_getRecommendation(self.region, user_id)
# Parses value of recommendation from DynamoDB JSON return value
tv_show = response['Item']['Result']['S']
user_name = response['Item']['UserName']['S']
# Server is healthy of RecommendationService returned the expected response
is_healthy = (tv_show == TEST) and (user_name == TEST)
# If the service dependency fails, capture diagnostic info
except Exception as e:
error_msg += str(traceback.format_exception_only(e.__class__, e))
# Based on the health assessment
# If it succeeded return a healthy code
# If it failed return a server failure code
message = ""
if (is_healthy):
self.send_response(200)
self.send_header('Content-type', 'text/html')
self.end_headers()
message += "
"
message += error_msg
# Add metadata
message += get_metadata()
self.wfile.write(
bytes(
html.format(Title="healthcheck", Content=message),
"utf-8"
)
)
return
# Utility function to consistently format how recommendations are displayed
def recommendation_message (user_name, tv_show, is_custom_reco):
if is_custom_reco:
tag_line = "your recommendation is"
else:
tag_line = "everyone enjoys this classic"
cell1 = "" + user_name + ", " + tag_line + ":"
cell2 = "" + tv_show + ""
reco_msg = "
" + "
" + cell1 + "
" + "
" + cell2 + "
" + "
"
return reco_msg
# Retrieve Metadata which can be useful to students
# For example to see which instance / AWS AZ they are hitting
def get_metadata():
metadata = '
EC2 Metadata
'
try:
message_parts = [
'account_id: %s' % ec2_metadata.account_id,
'ami_id: %s' % ec2_metadata.ami_id,
'availability_zone: %s' % ec2_metadata.availability_zone,
'instance_id: %s' % ec2_metadata.instance_id,
'instance_type: %s' % ec2_metadata.instance_type,
'private_hostname: %s' % ec2_metadata.private_hostname,
'private_ipv4: %s' % ec2_metadata.private_ipv4
]
metadata += ' '.join(message_parts)
except Exception:
metadata += "Running outside AWS"
return metadata
# This method mocks the call to the RecommendationService.
# Calls to the getRecommendation API are actually get_item
# calls to a dynamoDB table
def call_getRecommendation(region, user_id):
# It would be more efficient to create the clients once on init
# But in the lab we change permissions on the EC2 instance
# and this way we are sure to pick up the new credentials
session = boto3.Session()
# Setup client for DDB -- we will use this to mock a service dependency
ddb_client = session.client('dynamodb', region)
# Setup client for SSM -- we use this for parameters used as a
# enable/disable switch in the lab
ssm_client = session.client('ssm', region_name=region)
# Configure if mocked recomendation service is enabled or if it should simulate
# disabled (unreachable)
value = ssm_client.get_parameter(Name='RecommendationServiceEnabled')
dependency_enabled = value['Parameter']['Value'] == "true"
table_name = "RecommendationService" if dependency_enabled else "dependencyShouldFail"
# Call the RecommendationService
# (actually just a simply lookup in a DynamoDB table, which is acting as a mock for the RecommendationService)
response = ddb_client.get_item(
TableName=table_name,
Key={
'ServiceAPI': {
'S': 'getRecommendation',
},
'UserID': {
'N': user_id,
}
}
)
return response
# Initialize server
def run(argv):
try:
opts, args = getopt.getopt(
argv,
"hs:p:r:",
[
"help",
"server_ip=",
"server_port=",
"region="
]
)
except getopt.GetoptError:
print('server.py -s -p -r ')
sys.exit(2)
print(opts)
# Default value - will be over-written if supplied via args
server_port = 80
server_ip = '0.0.0.0'
try:
region = ec2_metadata.region
except:
region = 'us-east-2'
# Get commandline arguments
for opt, arg in opts:
if opt in ("-h", "--help"):
print('server.py -s -p -r ')
sys.exit()
elif opt in ("-s", "--server_ip"):
server_ip = arg
elif opt in ("-p", "--server_port"):
server_port = int(arg)
elif opt in ("-r", "--region"):
region = arg
# start server
print('starting server...')
server_address = (server_ip, server_port)
handler = partial(RequestHandler, region)
httpd = HTTPServer(server_address, handler)
print('running server...')
httpd.serve_forever()
if __name__ == "__main__":
run(sys.argv[1:])
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