Hi Guys!
Today, We will be discussing some of the better use-cases where we want to implement better solutions, which helps our entire Microservice/API integration painless.
As we drive towards more & more real-time applications such as mobile apps, IoT, and bots, we are engaging more microservice/API components in our technology stack. Moreover, We have witnessed that on many occasions, a full grown microservice environment leads to many unforeseen scenarios, which was not predicted or captured correctly.
To understand how a mesh-API architecture looks like, let us take one sample example for our case. Furthermore, what kind of problem we might face & how we can address.
Let us consider Airline online check-in as an example here.
There are following components are taking place irrespective of any airline ->
- Filling-up primary information such as First Name, Last Name, Address, Contact details, Passport & Booking No.
- We will have to choose a seat.
- We will need to provide the input for a meal (However, this is optional as the domestic flight may or may not have this based on the distance & budget)
- Finally, generations of Boarding-Pass.
If we decoupled our application here, we could create four inter-connected microservices to cater to our requirements. And this is shown in the given diagram –
From the above diagram, we can see that customer invokes a couple of related but independent services to finish the process of generating a Boarding-Pass. As per the diagram, initial requests reach the main Onboarding API & that results in cascading service calls & their successful response. In a developer’s term, this one we call it a “Happy Scenario!”
Nevertheless, developers do not always get this kind of rosy scenario. Sometimes, we encountered a scenario like this –
Suppose we see an issue with our Boarding-pass generation service, which may encounter some network or any fatal issue, which leads to a chain of failure to its parent services. Moreover, the result will be disastrous.
How can we handle such scenarios? There are a few guidelines that we can explore.
- Time-Out trigger while calling any service/s
- Building Asynchronous service
- Implementation of Circuit-Breaker
We can also use the standard workflow management or custom build workflow manager to improve that further (We will discuss this later in this blog).
We understood that our parent service should not wait for a longer time, where there is a significant delay from the child service. Otherwise, it will have a cascading effect & bring down the entire array of services and it.
However, the use of Circuit-Breaker is an advanced & better way to handle such scenarios. To keep this post small, We are not going to share all the codebase here. We will examine mainly two base codes.
Please find the current directory structure –
Let us consider implementing without the Circuit-Breaker. We have created the following functions & a custom Python library deployed for this demo. However, We will not discuss anything in this library today. We will release it in PyPi & share the post the update & detail functionality here later. This library is a Python-based lightweight workflow manager, which will continuously monitor any failed service & when connected – it will trigger it when connected.
From the above diagram, we can see that if we force “time-out” while calling our services, we can use this lightweight framework later whenever that service wake-up or establish a connection.
Please find the WhatsApp delivery through our microservice framework using this lightweight workflow framework.
We have used Visual studio code editor for this entire development of azure functions. And, the screen should look something like this –
We’ll discuss one the following two services –
- getSeatSelection
- getBoardingPass
We will also discuss the first script twice – one is with the standard time-out approach & another with the circuit-breaker.
- getSeatSelection ( This Microservice receives the inputs from its parent microservice & confirm the preferred seat-no selected by the passengers. )
##############################################
#### Written By: SATYAKI DE ####
#### Written On: 05-Oct-2020 ####
#### Modified On 05-Oct-2020 ####
#### ####
#### Objective: Scripts to choose the ####
#### seat for the passenger. ####
##############################################
import logging
import json
import time
import os
import ssl
import requests
import azure.functions as func
def callService(inputJson, urlPost, retryNo, eventFlag, maxRetryNo, maxTimeOut):
# Invoking getBoardingPass API
try:
# Bypassing SSL Authentication
try:
_create_unverified_https_context = ssl._create_unverified_context
except AttributeError:
# Legacy python that doesn't verify HTTPS certificates by default
pass
else:
# Handle target enviornment that doesn't support HTTPS verification
ssl._create_default_https_context = _create_unverified_https_context
# Providing the url bearer token
url = urlPost
json_data = inputJson
headers = {'content-type': "application/json", 'cache-control': "no-cache"}
# Failed case retry
retries = retryNo
success = False
return_description = 'N/A'
statusVal = 'Failed'
try:
while not success:
try:
# Getting response from web service
try:
strCheckMsg = 'Sending Payload - ' + str(retries)
logging.info(strCheckMsg)
response = requests.request("POST", url, data=json_data, headers=headers, verify=False, timeout=maxTimeOut)
resp_dict = json.loads(response.text)
statusVal = resp_dict['status']
return_description = resp_dict['description']
logging.info(statusVal)
except Exception as e:
x = str(e)
logging.info(x)
success = False
if (eventFlag == 'Boarding-Pass'):
str_R = "Boarding-Pass Json Response:: " + str(response.text)
else:
str_R = "Invalid flag options "
logging.info((str_R))
if len(response.text) > 80:
if str(response.status_code)[:1] == '2':
success = True
else:
wait = retries * 2
str_R1 = "retries Fail! Waiting " + str(wait) + " seconds and retrying!"
logging.info(str_R1)
time.sleep(wait)
retries += 1
# Checking maximum retries
if retries >= maxRetryNo:
success = True
raise Exception
else:
if str(response.status_code)[:1] == '2':
success = True
else:
# Checking maximum entries
if retries >= maxRetryNo:
success = True
raise Exception
retries += 1
except:
strVal = 'Retrying - ' + str(retries)
logging.info(strVal)
# Checking maximum entries
if retries >= maxRetryNo:
success = True
raise Exception
retries += 1
selection_flag = 'Y'
# Forming return JSON
jsonRet = {
"eventFlag": eventFlag,
"status":statusVal,
"description":return_description,
"computeFlag":selection_flag
}
xval = json.dumps(jsonRet)
return xval
except (ConnectionError, TimeoutError, InterruptedError) as e:
str_R8 = "Response from Server: " + str(response)
logging.info(str_R8)
str_R9 = "Sending payload to Webservice!"
logging.info(str_R9)
selection_flag = 'N'
# Forming return JSON
jsonRet = {
"eventFlag": eventFlag,
"status":"Lost",
"description":"Timed-Out or Connection Error or any I/O issue preventing the process. We're working on this!",
"computeFlag":selection_flag
}
xval = json.dumps(jsonRet)
return xval
except ValueError as e:
x = str(e)
logging.info(x)
selection_flag = 'N'
# Forming return JSON
jsonRet = {
"eventFlag": eventFlag,
"status":"Failed",
"description":"Please check the internal parameters compatibility with it's data-type!",
"computeFlag":selection_flag
}
xval = json.dumps(jsonRet)
return xval
except Exception as e:
x = str(e)
logging.info(x)
selection_flag = 'N'
# Forming return JSON
jsonRet = {
"eventFlag": eventFlag,
"status":"Accepted",
"description":"Maximum rerties to the Boarding-Pass service is now reached. We're working offline to get that for you. Please rerty after 4 hours in case if you haven't received it or you can directly call customer care number!",
"computeFlag":selection_flag
}
xval = json.dumps(jsonRet)
return xval
except Exception as e:
x = str(e)
logging.info(x)
selection_flag = 'N'
# Forming return JSON
jsonRet = {
"eventFlag": eventFlag,
"status":"Failed",
"description":"DevOps Engineer is looking into this. Please try after some time!",
"computeFlag":selection_flag
}
xval = json.dumps(jsonRet)
return xval
def main(req: func.HttpRequest) -> func.HttpResponse:
logging.info('Invoking Seat-Selection generation service.')
# Getting System Variable from local settings file
strVal = 'Parameter Recieved :' + os.environ['maxRetry']
logging.info(strVal)
# Capturing parameters from local settings
max_retries = int(os.environ['maxRetry'])
c_url = os.environ['cUrlBP']
# Printing input Payload
str_val = 'Input Payload:: ' + str(req.get_json())
logging.info(str_val)
strMainCheck = str(req.get_json())
# variable
x_status = 'Success'
if (strMainCheck != ''):
# Capturing individual elements
sourceLeg = req.params.get('sourceLeg')
destinationLeg = req.params.get('destinationLeg')
boardingClass = req.params.get('boardingClass')
preferredSeatNo = req.params.get('preferredSeatNo')
travelPassport = req.params.get('travelPassport')
bookingNo = req.params.get('bookingNo')
travelerEmail = req.params.get('travelerEmail')
travelerMobile = req.params.get('travelerMobile')
# Checking Individual Elements
if not sourceLeg:
try:
req_body = req.get_json()
except ValueError:
pass
else:
sourceLeg = req_body.get('sourceLeg')
if not destinationLeg:
try:
req_body = req.get_json()
except ValueError:
pass
else:
destinationLeg = req_body.get('destinationLeg')
if not boardingClass:
try:
req_body = req.get_json()
except ValueError:
pass
else:
boardingClass = req_body.get('boardingClass')
if not preferredSeatNo:
try:
req_body = req.get_json()
except ValueError:
pass
else:
preferredSeatNo = req_body.get('preferredSeatNo')
if not travelPassport:
try:
req_body = req.get_json()
except ValueError:
pass
else:
travelPassport = req_body.get('travelPassport')
if not bookingNo:
try:
req_body = req.get_json()
except ValueError:
pass
else:
bookingNo = req_body.get('bookingNo')
if not travelerEmail:
try:
req_body = req.get_json()
except ValueError:
pass
else:
travelerEmail = req_body.get('travelerEmail')
if not travelerMobile:
try:
req_body = req.get_json()
except ValueError:
pass
else:
travelerMobile = req_body.get('travelerMobile')
if (
(sourceLeg != '') & (destinationLeg != '') & (boardingClass != '') &
(preferredSeatNo != '') & (travelPassport != '') & (bookingNo != '') &
((travelerEmail != '') | (travelerMobile != ''))
):
x_description = "Seat-Selection Successfully Processed!"
# Preparing Payload for boarding-pass
json_str_boarding = {
"sourceLeg": sourceLeg,
"destinationLeg": destinationLeg,
"boardingClass": boardingClass,
"confirmedSeatNo": preferredSeatNo,
"travelPassport": travelPassport,
"bookingNo": bookingNo,
"travelerEmail": travelerEmail,
"travelerMobile": travelerMobile
}
jsonBoardingInput = json.dumps(json_str_boarding)
eventFlag = 'Boarding-Pass'
retryNoBase = 1
maxTimeOut = 2.5
# Invoking getBoardingPass API
microCallsBP = callService(jsonBoardingInput, c_url, retryNoBase, eventFlag, max_retries, maxTimeOut)
# Extracting seat_selection_flag
resp_dict = json.loads(microCallsBP)
x_status = resp_dict['status']
x_description = resp_dict['description']
# Capturing description value based on the logic
logging.info(x_description)
# Formatting return Payload
json_str = {
"description": x_description,
"status": x_status,
"sourceLeg": sourceLeg,
"destinationLeg": destinationLeg,
"boardingClass": boardingClass,
"confirmedSeatNo": preferredSeatNo,
"travelPassport": travelPassport,
"bookingNo": bookingNo,
"travelerEmail": travelerEmail,
"travelerMobile": travelerMobile
}
xval = json.dumps(json_str)
return func.HttpResponse(xval, status_code=200)
else:
json_str = {
"description": "Missing mandatory Email or Phone Number!",
"status": "Failed",
"sourceLeg": sourceLeg,
"destinationLeg": destinationLeg,
"boardingClass": boardingClass,
"confirmedSeatNo": preferredSeatNo,
"travelPassport": travelPassport,
"bookingNo": bookingNo,
"travelerEmail": travelerEmail,
"travelerMobile": travelerMobile
}
xval = json.dumps(json_str)
return func.HttpResponse(xval,status_code=200)
else:
json_str = {
"description": "Missing entire payload!",
"status": "Failed",
"sourceLeg": "N/A",
"destinationLeg": "N/A",
"boardingClass": "N/A",
"confirmedSeatNo": "N/A",
"travelPassport": "N/A",
"bookingNo": "N/A",
"travelerEmail": "N/A",
"travelerMobile": "N/A"
}
xval = json.dumps(json_str)
return func.HttpResponse(xval,status_code=200)
There are a few key snippets that we would like to discuss here.
# Getting response from web service
try:
strCheckMsg = 'Sending Payload - ' + str(retries)
logging.info(strCheckMsg)
response = requests.request("POST", url, data=json_data, headers=headers, verify=False, timeout=maxTimeOut)
resp_dict = json.loads(response.text)
statusVal = resp_dict['status']
return_description = resp_dict['description']
logging.info(statusVal)
except Exception as e:
x = str(e)
logging.info(x)
success = False
From the above snippet, we can see that we are using time-out based on our understanding of response time or the max SLA agreed upon for that particular service.
If we get the response, we are capturing the status as well as the description from its child service & capturing it in our log, which will look something like this –
2. getBoardingPass ( This Microservice receives the input from its parent service & confirm the autogenerated boarding pass shared with their WhatsApp number.)
##############################################
#### Written By: SATYAKI DE ####
#### Written On: 02-Oct-2020 ####
#### Modified On 04-Oct-2020 ####
#### ####
#### Objective: Scripts to generate the ####
#### boarding pass for the passenger. ####
##############################################
import logging
import json
import hashlib
import time
import os
import random
from twilio.rest import Client
from twilio.base.exceptions import TwilioRestException
import azure.functions as func
def main(req: func.HttpRequest) -> func.HttpResponse:
try:
logging.info('Invoking Boarding-Pass generation service.')
# Getting System Variable from local settings file
strVal = 'Parameter Recieved :' + os.environ['timeOut']
logging.info(strVal)
sleep_time = int(os.environ['timeOut'])
# Printing input Payload
str_val = 'Input Payload:: ' + str(req.get_json())
logging.info(str_val)
strMainCheck = str(req.get_json())
if (strMainCheck != ''):
# Capturing individual elements
sourceLeg = req.params.get('sourceLeg')
destinationLeg = req.params.get('destinationLeg')
boardingClass = req.params.get('boardingClass')
confirmedSeatNo = req.params.get('confirmedSeatNo')
travelPassport = req.params.get('travelPassport')
bookingNo = req.params.get('bookingNo')
travelerEmail = req.params.get('travelerEmail')
travelerMobile = req.params.get('travelerMobile')
# Checking Individual Elements
if not sourceLeg:
try:
req_body = req.get_json()
except ValueError:
pass
else:
sourceLeg = req_body.get('sourceLeg')
if not destinationLeg:
try:
req_body = req.get_json()
except ValueError:
pass
else:
destinationLeg = req_body.get('destinationLeg')
if not boardingClass:
try:
req_body = req.get_json()
except ValueError:
pass
else:
boardingClass = req_body.get('boardingClass')
if not confirmedSeatNo:
try:
req_body = req.get_json()
except ValueError:
pass
else:
confirmedSeatNo = req_body.get('confirmedSeatNo')
if not travelPassport:
try:
req_body = req.get_json()
except ValueError:
pass
else:
travelPassport = req_body.get('travelPassport')
if not bookingNo:
try:
req_body = req.get_json()
except ValueError:
pass
else:
bookingNo = req_body.get('bookingNo')
if not travelerEmail:
try:
req_body = req.get_json()
except ValueError:
pass
else:
travelerEmail = req_body.get('travelerEmail')
if not travelerMobile:
try:
req_body = req.get_json()
except ValueError:
pass
else:
travelerMobile = req_body.get('travelerMobile')
# Mimicking network latency or issues
random_sleep_time = random.randint(1, sleep_time)
time.sleep(random_sleep_time)
child_cond_time = float(os.environ['timeOutChild'])
# Important Details capture in log
strRandSleepTime = 'Network Generated delay: ' + str(random_sleep_time) + ' sec'
logging.info(strRandSleepTime)
strThreadTimeOut = 'Orphan microservice kill time: ' + str(child_cond_time) + ' sec'
logging.info(strThreadTimeOut)
# Handling orphan microservice
if (random_sleep_time > child_cond_time):
strCondChk = 'Rasing exception to avoid orphan microservice call!'
logging.info(strCondChk)
raise Exception
if (
(sourceLeg != '') & (destinationLeg != '') & (boardingClass != '') &
(confirmedSeatNo != '') & (travelPassport != '') & (bookingNo != '') &
((travelerEmail != '') | (travelerMobile != ''))
):
# Generating simulated barcode
# Concatenating Key Values
strImpVal = str(sourceLeg)+str(destinationLeg)+str(boardingClass)+str(confirmedSeatNo)+str(travelPassport)+str(bookingNo)+str(travelerEmail)+str(travelerMobile)
# Printing Concatenated Value
logging.info(strImpVal)
# m.update(strImpVal)
xbarcode = hashlib.md5(strImpVal.encode("utf").strip()).hexdigest().upper()
# Formatting return Payload
json_str = {
"description": "Boarding-Pass Successfully Generated!",
"status": "Success",
"sourceLeg": sourceLeg,
"destinationLeg": destinationLeg,
"boardingClass": boardingClass,
"confirmedSeatNo": confirmedSeatNo,
"travelPassport": travelPassport,
"bookingNo": bookingNo,
"travelerEmail": travelerEmail,
"travelerMobile": travelerMobile,
"barCode": xbarcode
}
xval = json.dumps(json_str)
# Calling Twilio API to send WhatsApp Message
try:
strComAPI = 'Calling WhatsApp API'
logging.info(strComAPI)
account_sid = str(os.environ['accountSid'])
auth_token = os.environ['authToken']
mobPr = os.environ['mobPredicate']
fromMob = mobPr + os.environ['fromMobile']
toMob = mobPr + travelerMobile
client = Client(account_sid, auth_token)
msgBody = 'Your Boarding-Pass from ' + sourceLeg + ' to ' + destinationLeg + ' are as follows --> Boarding Class (' + boardingClass + ') - ' + 'Seat (' + confirmedSeatNo + ') - Gate (A' + str(random_sleep_time) + ') - ' + 'Bar Code (' + xbarcode + ')'
message = client.messages.create(from_=fromMob, body=msgBody, to=toMob)
msgStat = message.status
if (msgStat.upper() == 'QUEUED') | (msgStat.upper() == 'DELIEVERD') | (msgStat.upper() == 'SUCCESS'):
return func.HttpResponse(xval, status_code=200)
else:
# Formatting return Payload
json_str = {
"description": "Encountered some technical issue. Don't worry - we're working on it!",
"status": "Accepted",
"sourceLeg": sourceLeg,
"destinationLeg": destinationLeg,
"boardingClass": boardingClass,
"confirmedSeatNo": confirmedSeatNo,
"travelPassport": travelPassport,
"bookingNo": bookingNo,
"travelerEmail": travelerEmail,
"travelerMobile": travelerMobile,
"barCode": xbarcode
}
xval = json.dumps(json_str)
return func.HttpResponse(xval, status_code=200)
except TwilioRestException as e:
x = str(e)
logging.info(x)
# Formatting return Payload
json_str = {
"description": "Encountered some technical issue. Don't worry - we're working on it!",
"status": "Delivery Failed!",
"sourceLeg": sourceLeg,
"destinationLeg": destinationLeg,
"boardingClass": boardingClass,
"confirmedSeatNo": confirmedSeatNo,
"travelPassport": travelPassport,
"bookingNo": bookingNo,
"travelerEmail": travelerEmail,
"travelerMobile": travelerMobile,
"barCode": xbarcode
}
xval = json.dumps(json_str)
return func.HttpResponse(xval, status_code=200)
else:
xbarcode = 'Not Generated!'
json_str = {
"description": "Missing mandatory Email or Phone Number!",
"status": "Failed",
"sourceLeg": sourceLeg,
"destinationLeg": destinationLeg,
"boardingClass": boardingClass,
"confirmedSeatNo": confirmedSeatNo,
"travelPassport": travelPassport,
"bookingNo": bookingNo,
"travelerEmail": travelerEmail,
"travelerMobile": travelerMobile,
"barCode": xbarcode
}
xval = json.dumps(json_str)
return func.HttpResponse(xval,status_code=200)
else:
xbarcode = 'Not Generated!'
json_str = {
"description": "Missing entire payload!",
"status": "Failed",
"sourceLeg": "N/A",
"destinationLeg": "N/A",
"boardingClass": "N/A",
"confirmedSeatNo": "N/A",
"travelPassport": "N/A",
"bookingNo": "N/A",
"travelerEmail": "N/A",
"travelerMobile": "N/A",
"barCode": xbarcode
}
xval = json.dumps(json_str)
return func.HttpResponse(xval,status_code=200)
except Exception as e:
x = str(e)
logging.info(x)
x_description = 'Time-out due to network delay!'
logging.info(x_description)
xbarcode = 'Not Generated!'
json_str = {
"description": x_description,
"status": "Failed",
"sourceLeg": "N/A",
"destinationLeg": "N/A",
"boardingClass": "N/A",
"confirmedSeatNo": "N/A",
"travelPassport": "N/A",
"bookingNo": "N/A",
"travelerEmail": "N/A",
"travelerMobile": "N/A",
"barCode": xbarcode
}
xval = json.dumps(json_str)
return func.HttpResponse(xval,status_code=200)
Let us explore some of the vital snippets –
# Mimicking network latency or issues
random_sleep_time = random.randint(1, sleep_time)
time.sleep(random_sleep_time)
child_cond_time = float(os.environ['timeOutChild'])
# Important Details capture in log
strRandSleepTime = 'Network Generated delay: ' + str(random_sleep_time) + ' sec'
logging.info(strRandSleepTime)
strThreadTimeOut = 'Orphan microservice kill time: ' + str(child_cond_time) + ' sec'
logging.info(strThreadTimeOut)
# Handling orphan microservice
if (random_sleep_time > child_cond_time):
strCondChk = 'Rasing exception to avoid orphan microservice call!'
logging.info(strCondChk)
raise Exception
We tried to create a random wait time, which will produce a sudden network latency or mimicking potential network/time-out/connection issues. Also, we want to finish this thread to avoid any unwanted WhatsApp message trigger via Twilio-API.
And, when we want to test the parent Seat-Selection service through postman, it will show the following response –
We must have noticed that since the boarding pass also captured the seat details; hence, we are addressing them together here.
For successful execution, we can see a similar message –
However, if we want to handle this better, we can use “Circuit-Breaker.”
Let us understand what this is. Since our childhood, we all know that when there is an electricity fluctuation happens frequently, to prevent all the electrical appliances, we deploy this small device that will disconnect the power between our house’s primary grid with all the appliances at our home. It will prevent these devices from getting exposed.
The same concept has been implemented for Microservice architecture as well.
The above diagram shows that using a circuit breaker will continue all its previous parent services in everyday activities without any issues.
The above diagram shows that it will stop all the parent services if the child service is not responding based on the threshold count.
The above diagram shows that once there is a “STOP” event captured. It will wait for a few seconds before it will allow a few services to test whether the impacted service is ready to consume further requests or not. This way, it can control the threading bottleneck.
The next diagram will give us the distinct state of a “Circuit Breaker.”
The above diagram shows that using a circuit breaker will prevent all its previous parent services. It will maintain a threshold of failures & successful data points. It will allow services to invoke the impacted service either entirely, partially, or even completely block it depending on the situation.
Let us revise the code & review it together –
3. getSeatSelection ( This Microservice receives the inputs from its parent microservice & confirm the preferred seat-no selected by the passengers – using Circuit-Breaker. )
##############################################
#### Written By: SATYAKI DE ####
#### Written On: 05-Oct-2020 ####
#### Modified On 05-Oct-2020 ####
#### ####
#### Objective: Scripts to choose the ####
#### seat for the passenger. ####
##############################################
import logging
import json
import time
import os
import ssl
import requests
import azure.functions as func
from circuitbreaker import CircuitBreaker
class BoardingPassCircuitBreaker(CircuitBreaker):
FAILURE_THRESHOLD = 10
RECOVERY_TIMEOUT = 60
EXPECTED_EXCEPTION = TimeoutError
@BoardingPassCircuitBreaker()
def callService(inputJson, urlPost, retryNo, eventFlag, maxRetryNo, maxTimeOut):
# Invoking getBoardingPass API
try:
# Bypassing SSL Authentication
try:
_create_unverified_https_context = ssl._create_unverified_context
except AttributeError:
# Legacy python that doesn't verify HTTPS certificates by default
pass
else:
# Handle target enviornment that doesn't support HTTPS verification
ssl._create_default_https_context = _create_unverified_https_context
# Providing the url bearer token
url = urlPost
json_data = inputJson
headers = {'content-type': "application/json", 'cache-control': "no-cache"}
# Failed case retry
retries = retryNo
success = False
return_description = 'N/A'
statusVal = 'Failed'
try:
while not success:
try:
# Getting response from web service
try:
strCheckMsg = 'Sending Payload - ' + str(retries)
logging.info(strCheckMsg)
response = requests.request("POST", url, data=json_data, headers=headers, verify=False, timeout=maxTimeOut)
resp_dict = json.loads(response.text)
statusVal = resp_dict['status']
return_description = resp_dict['description']
logging.info(statusVal)
except Exception as e:
x = str(e)
logging.info(x)
success = False
if (eventFlag == 'Boarding-Pass'):
str_R = "Boarding-Pass Json Response:: " + str(response.text)
else:
str_R = "Invalid flag options "
logging.info((str_R))
if len(response.text) > 80:
if str(response.status_code)[:1] == '2':
success = True
else:
wait = retries * 2
str_R1 = "retries Fail! Waiting " + str(wait) + " seconds and retrying!"
logging.info(str_R1)
time.sleep(wait)
retries += 1
# Checking maximum retries
if retries >= maxRetryNo:
success = True
raise Exception
else:
if str(response.status_code)[:1] == '2':
success = True
else:
# Checking maximum entries
if retries >= maxRetryNo:
success = True
raise Exception
retries += 1
except:
strVal = 'Retrying - ' + str(retries)
logging.info(strVal)
# Checking maximum entries
if retries >= maxRetryNo:
success = True
raise Exception
retries += 1
selection_flag = 'Y'
# Forming return JSON
jsonRet = {
"eventFlag": eventFlag,
"status":statusVal,
"description":return_description,
"computeFlag":selection_flag
}
xval = json.dumps(jsonRet)
return xval
except (ConnectionError, TimeoutError, InterruptedError) as e:
str_R8 = "Response from Server: " + str(response)
logging.info(str_R8)
str_R9 = "Sending payload to Webservice!"
logging.info(str_R9)
selection_flag = 'N'
# Forming return JSON
jsonRet = {
"eventFlag": eventFlag,
"status":"Lost",
"description":"Timed-Out or Connection Error or any I/O issue preventing the process. We're working on this!",
"computeFlag":selection_flag
}
xval = json.dumps(jsonRet)
return xval
except ValueError as e:
x = str(e)
logging.info(x)
selection_flag = 'N'
# Forming return JSON
jsonRet = {
"eventFlag": eventFlag,
"status":"Failed",
"description":"Please check the internal parameters compatibility with it's data-type!",
"computeFlag":selection_flag
}
xval = json.dumps(jsonRet)
return xval
except Exception as e:
x = str(e)
logging.info(x)
selection_flag = 'N'
# Forming return JSON
jsonRet = {
"eventFlag": eventFlag,
"status":"Accepted",
"description":"Maximum rerties to the Boarding-Pass service is now reached. We're working offline to get that for you. Please rerty after 4 hours in case if you haven't received it or you can directly call customer care number!",
"computeFlag":selection_flag
}
xval = json.dumps(jsonRet)
return xval
except Exception as e:
x = str(e)
logging.info(x)
selection_flag = 'N'
# Forming return JSON
jsonRet = {
"eventFlag": eventFlag,
"status":"Failed",
"description":"DevOps Engineer is looking into this. Please try after some time!",
"computeFlag":selection_flag
}
xval = json.dumps(jsonRet)
return xval
def main(req: func.HttpRequest) -> func.HttpResponse:
logging.info('Invoking Seat-Selection generation service.')
# Getting System Variable from local settings file
strVal = 'Parameter Recieved :' + os.environ['maxRetry']
logging.info(strVal)
# Capturing parameters from local settings
max_retries = int(os.environ['maxRetry'])
c_url = os.environ['cUrlBP']
# Printing input Payload
str_val = 'Input Payload:: ' + str(req.get_json())
logging.info(str_val)
strMainCheck = str(req.get_json())
# variable
x_status = 'Success'
if (strMainCheck != ''):
# Capturing individual elements
sourceLeg = req.params.get('sourceLeg')
destinationLeg = req.params.get('destinationLeg')
boardingClass = req.params.get('boardingClass')
preferredSeatNo = req.params.get('preferredSeatNo')
travelPassport = req.params.get('travelPassport')
bookingNo = req.params.get('bookingNo')
travelerEmail = req.params.get('travelerEmail')
travelerMobile = req.params.get('travelerMobile')
# Checking Individual Elements
if not sourceLeg:
try:
req_body = req.get_json()
except ValueError:
pass
else:
sourceLeg = req_body.get('sourceLeg')
if not destinationLeg:
try:
req_body = req.get_json()
except ValueError:
pass
else:
destinationLeg = req_body.get('destinationLeg')
if not boardingClass:
try:
req_body = req.get_json()
except ValueError:
pass
else:
boardingClass = req_body.get('boardingClass')
if not preferredSeatNo:
try:
req_body = req.get_json()
except ValueError:
pass
else:
preferredSeatNo = req_body.get('preferredSeatNo')
if not travelPassport:
try:
req_body = req.get_json()
except ValueError:
pass
else:
travelPassport = req_body.get('travelPassport')
if not bookingNo:
try:
req_body = req.get_json()
except ValueError:
pass
else:
bookingNo = req_body.get('bookingNo')
if not travelerEmail:
try:
req_body = req.get_json()
except ValueError:
pass
else:
travelerEmail = req_body.get('travelerEmail')
if not travelerMobile:
try:
req_body = req.get_json()
except ValueError:
pass
else:
travelerMobile = req_body.get('travelerMobile')
if (
(sourceLeg != '') & (destinationLeg != '') & (boardingClass != '') &
(preferredSeatNo != '') & (travelPassport != '') & (bookingNo != '') &
((travelerEmail != '') | (travelerMobile != ''))
):
x_description = "Seat-Selection Successfully Processed!"
# Preparing Payload for boarding-pass
json_str_boarding = {
"sourceLeg": sourceLeg,
"destinationLeg": destinationLeg,
"boardingClass": boardingClass,
"confirmedSeatNo": preferredSeatNo,
"travelPassport": travelPassport,
"bookingNo": bookingNo,
"travelerEmail": travelerEmail,
"travelerMobile": travelerMobile
}
jsonBoardingInput = json.dumps(json_str_boarding)
eventFlag = 'Boarding-Pass'
retryNoBase = 1
maxTimeOut = 2.5
# Invoking getBoardingPass API
microCallsBP = callService(jsonBoardingInput, c_url, retryNoBase, eventFlag, max_retries, maxTimeOut)
# Extracting seat_selection_flag
resp_dict = json.loads(microCallsBP)
x_status = resp_dict['status']
x_description = resp_dict['description']
# Capturing description value based on the logic
logging.info(x_description)
# Formatting return Payload
json_str = {
"description": x_description,
"status": x_status,
"sourceLeg": sourceLeg,
"destinationLeg": destinationLeg,
"boardingClass": boardingClass,
"confirmedSeatNo": preferredSeatNo,
"travelPassport": travelPassport,
"bookingNo": bookingNo,
"travelerEmail": travelerEmail,
"travelerMobile": travelerMobile
}
xval = json.dumps(json_str)
return func.HttpResponse(xval, status_code=200)
else:
json_str = {
"description": "Missing mandatory Email or Phone Number!",
"status": "Failed",
"sourceLeg": sourceLeg,
"destinationLeg": destinationLeg,
"boardingClass": boardingClass,
"confirmedSeatNo": preferredSeatNo,
"travelPassport": travelPassport,
"bookingNo": bookingNo,
"travelerEmail": travelerEmail,
"travelerMobile": travelerMobile
}
xval = json.dumps(json_str)
return func.HttpResponse(xval,status_code=200)
else:
json_str = {
"description": "Missing entire payload!",
"status": "Failed",
"sourceLeg": "N/A",
"destinationLeg": "N/A",
"boardingClass": "N/A",
"confirmedSeatNo": "N/A",
"travelPassport": "N/A",
"bookingNo": "N/A",
"travelerEmail": "N/A",
"travelerMobile": "N/A"
}
xval = json.dumps(json_str)
return func.HttpResponse(xval,status_code=200)
Let us review the key snippets –
from circuitbreaker import CircuitBreaker
class BoardingPassCircuitBreaker(CircuitBreaker):
FAILURE_THRESHOLD = 10
RECOVERY_TIMEOUT = 60
EXPECTED_EXCEPTION = TimeoutError
@BoardingPassCircuitBreaker()
def callService(inputJson, urlPost, retryNo, eventFlag, maxRetryNo, maxTimeOut):
# Invoking getBoardingPass API
try:
<Code>
# Forming return JSON
jsonRet = {
"eventFlag": eventFlag,
"status":statusVal,
"description":return_description,
"computeFlag":selection_flag
}
xval = json.dumps(jsonRet)
return xval
except Exception as e:
x = str(e)
logging.info(x)
selection_flag = 'N'
# Forming return JSON
jsonRet = {
"eventFlag": eventFlag,
"status":"Failed",
"description":"DevOps Engineer is looking into this. Please try after some time!",
"computeFlag":selection_flag
}
xval = json.dumps(jsonRet)
return xval
We have put the microservice call into a function & then mark it as a circuit-breaker method. Also, we have enforced some custom settings in our main circuit-breaker class as well.
Moreover, here are some of our main API sample outputs, i.e., “getOnBoarding,” depending on the child-services’ availability.
Please click the above image gallery to see all the combinations of responses.
Finally, here is the WhatsApp message if that call successful. We have used Twilio API to exchange the text.
Please find the dependent package from requirements.txt ->
azure-functions==1.4.0
certifi==2020.6.20
chardet==3.0.4
circuitbreaker==1.3.1
idna==2.10
numpy==1.19.2
pandas==1.1.2
PyJWT==1.7.1
python-dateutil==2.8.1
pytz==2020.1
requests==2.24.0
six==1.15.0
twilio==6.45.4
urllib3==1.25.10
So, finally, we have done it.
I’ll bring some more exciting topic in the coming days from the Python verse.
Till then, Happy Avenging! 😀
Note: All the data & scenario posted here are representational data & scenarios & available over the internet & for educational purpose only.
Satyaki De's Blog 
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