HTTP request -to- AWS Lambda Python function -to- AGOL

Question

I want to make an HTTP GET request to AGOL, but I want to route the request through a Python function.

Since I can't host the Python function on AGOL (more info here), I'd like to use AWS-Lambda instead.

HTTP GET request ➔ AWS Lambda Python function ➔ AGOL

What would it take to configure AWS Lambda so that it can serve as a middle tier between the HTTP GET request and AGOL?

Answer 1

Here's a sample AWS Lambda setup from a colleague:

1. Create an AWS account (free).
2. In AWS Lambda, create a new function.
   • Enter a function name and Runtime ➔ Python 3.7
3. Write the function.
   • This sample script receives an ASSET_ID value from a URL, processes it with Python, and sends additional requests to AGOL. It returns a JSON dictionary.

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from urllib.parse import urlencode
from urllib.request import Request, urlopen
import json
# Get a security token to append to all requests
def GetToken():
 username = '<my username>'
 password = '<my password>'
 url = 'https://www.arcgis.com/sharing/rest/generateToken' 
 post_fields = {'username': username,'password':password,'expiration':'60','client':'referer','referer':'http://www.arcgis.com','f':'json' }
 request = Request(url, urlencode(post_fields).encode())
 out = urlopen(request).read().decode()
 resp_dict = json.loads(out)
 # print (resp_dict['token'])
 return resp_dict['token']
# Query a feature service with a where clause returning all fields. Function returns a json dictionary
def queryFeatureService(url,token,where):
 post_fields = {'token': token,'where':where,'outfields':'*','returngeometry':'false','f':'json' }
 request = Request(url, urlencode(post_fields).encode())
 out = urlopen(request).read().decode()
 resp_dict = json.loads(out)
 return resp_dict
# Get the zone value from the matching Active Transportation feature 
def GetZone(jsonFeatures,zoneField):
 for feature in jsonFeatures['features']:
 # print (feature['attributes']['ZONE_'])
 return feature['attributes'][zoneField]
# Query with ASSET_ID, returning the workorder record with a new "ZONE_" field added from the matching Transportation layer
# 'lambda_handler' is the main function for Lambda. Code starts here when called
def lambda_handler(event, context):
 urlWorkorders = 'https://services.arcgis.com/Akv3yjcvcvmR0q1R/ArcGIS/rest/services/<my AGOL account name>/FeatureServer/0/query' 
 urlActiveTransportationPoints = 'https://services.arcgis.com/Akv3yjcvcvmR0q1R/ArcGIS/rest/services/Active_Transportation_Points/FeatureServer/0/query'
 token = GetToken() 
 ASSET_ID = event["queryStringParameters"]['asset_id']
 
 jsonWorkorder = queryFeatureService(urlWorkorders, token,"ASSET_ID = '" + ASSET_ID + "'")
 # JSON for the new "ZONE_" field, appends to return Workorder JSON object to give it this missing field
 fldZone = {'name':'ZONE_','type':'esriFieldTypeString','alias':'ZONE_','sqlType':'sqlTypeOther','length':15,'domain':None,'defaultValue':None}
 jsonWorkorder['fields'].append(fldZone)
 # Query the Active Transportation points with the same ASSET_ID
 jsonActiveTransportation = queryFeatureService(urlActiveTransportationPoints,token,"ASSET_ID = '" + ASSET_ID + "'")
 # Get the ZONE_ value
 zone = GetZone(jsonActiveTransportation,'ZONE_')
 # Set the ZONE_ value in the ZONE_ field that was added to workorders
 jsonWorkorder['features'][0]['attributes']['ZONE_'] = zone
 # return (jsonWorkorder)
 return {
 'statusCode': 200,
 'headers': {
 'Access-Control-Allow-Origin' : '*',
 'Access-Control-Allow-Headers' : '*'
 
 },
 'body': json.dumps(jsonWorkorder)
 }

---

4. Choose Add Trigger ➔ API Gateway
5. Choose Create a new API, REST API, Security ➔ Open
6. Open API Gateway: workorder-API hyperlink
7. Actions ➔ Create method ➔ GET ➔ configure as follows:
   • enter image description here
   • Save
8. Click Method Request header link ➔ expand Query String Parameters
9. Add query string "asset_id"

---

Conclusion:

It's a pretty interesting solution that could be useful for people who have similar requirements.

• I have more detailed instructions with screen captures in a PDF. If anyone wants it, just ask.
• I have a related question here: Query an ArcGIS Online FC via an HTTP request

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A note about security:

The AWS Lambda function specifies/stores the AGOL username and password. This freaked me out at first.

However, since the username and password are server-side, they are never exposed to the client user.

• In theory, we could write this same function as an AJAX call in JavaScript, but we would need to embed the credentials in the web code, making it unsecure, so that's why a server-side function is needed.

• Additionally, we could alter the Lambda function to pass an AGOL-registered app's clientID and Secret for more granular access control—which would not have my username and password embedded in the function.

• More info here: ArcGIS Web AppBuilder (Developer Edition). See the "Provide an app ID for Web AppBuilder" section (not just limited to just WAB, but for any app that needs a ClientID and Secret).

Answer 2

Thanks for your answer above but do you need to install any specific libraries or other tools to get it to run in AWS?

• User1974: I got help from a developer I know. So he'd have to answer that question.