I have a setup where we use API gateway, a json mapping template in the integration request where we access URL parameters as such:
"input":{
"my_int":"$input.params('someurlparam')"
},
I then access this variable in my Python lambda. This all works but I am getting inconsistent results in my lambda, sometimes the param is detected as an int and sometimes as a string. Different applications/testers accessing the api are getting different results and I have had to implement isinstance(my_int, str) checks and conversions in my lambda (I want to avoid this). How can I ensure the variable is parsed as an int prior to hitting my lambda?
Related
I'm trying to call a basic lambda from my API Gateway console. The lambda has an input taken in by the event called filterBy.
I created a query string called filterBy however, when I try to invoke the lambda I get the error:
{errorMessage: {'statusCode': 500, 'body': '{"msg": "KeyError(\'filterBy\')"}'}}
Presumably because the piece of code in my lambda
event['filterBy'] is not finding a filterBy in the event. What do I need to do so that I can get the filterBy in the event from the API Gateway console? I understand this is probably quite simple but I surprisingly cannot find anything about this so any help would be appreciated.
Based on the integration type, approach can be vary.
1. Lambda custom integrations:
Looks like you are trying to use Lambda custom integrations. If that is the case you have to add a mapping template as below.
(under the Integration Request -> Mapping Templates --> Add mapping template)
{
"filterBy": "$input.params('filterBy')"
}
Please refer this article or this video for more info.
2. Lambda proxy integrations:
If you are using Lambada proxy integration (either as REST API or as HTTP APIs), then instead of event['filterBy'], you have to access the queryStringParameters first and then access the relevant query param.
event['queryStringParameters']['filterBy']
And another thing is: once you modify something in API GW, please make sure to deploy and wait some time before test. :)
I am trying to build a system where multiple APIs gateway instances should execute the same lambda function.
My problem is that I would like to change only the lambda configuration in function of the API gateway used.
Let's take the name of a database as an example that should change if the lambda is being triggered from one API or the other.
Example:
API Gateways:
https://my-first-api-gateway.execute-api.eu-west-1.amazonaws.com
https://my-second-api-gateway.execute-api.eu-west-1.amazonaws.com
I then have one lambda function being called by the two APIs: say_hello.
This function has to retrieve a quote from a database. If the function has been called from my-first-api-gateway the lambda function has to use my_first_database and if the function has been called from my-second-api-gateway, it has to use my_second_database.
The only solution I came with is to deploy as many lambda functions as I have API Gateways. And then use environment variables to store my database name.
I don't like my solution because when I update a single line of code I'll have to redeploy all of my lambda functions.. (if I have 300 different databases to use, that would mean to update 300 lambda functions at once..)
Thank you for your ideas on this subject!
If you use a Lambda-Proxy integration you should be fine.
Full details of the event can be found here, however critically the headers Host, origin and Referer all point the the API Gateway uri:
"headers": {
"Host": "j3ap25j034.execute-api.eu-west-2.amazonaws.com",
"origin": "https://j3ap25j034.execute-api.eu-west-2.amazonaws.com",
"Referer": "https://j3ap25j034.execute-api.eu-west-2.amazonaws.com/dev/"
}
Therefore it should be fairly trivial for you to branch/look-up your database behaviour from this information.
I have a client facing API that takes a query parameter Time. The format is 14:00:00. Originally it would pass through this query parameter to the back end endpoint. However the back end endpoint (that I do not control) is now expecting time in the format 0001-01-01T14:00:00.
Is it possible to to modify the value of the query param before passing it on in AWS API Gateway?
I know you can modify the request body with a mapping template, and in the template you can access the queryParameters, but can you change them so that it modifies the actual request made to the back end?
I saw this:
https://forums.aws.amazon.com/thread.jspa?messageID=696524򪃌
but the user said he gave up trying to modify
Potential workaround I can think of right now are pass the parameters to a lambda and have the lambda build and make the request with modified values, with the response as the return value for the lambda
For now one can overrides query string in Mapping Templates using velocity templates e.g:
$context.requestOverride.querystring.time="_your_transformed_data_"
There is docs
I think you basically answered your own question :)
There is no way to transform query or header request parameters. All transformations need to happen in the body mapping template.
Best workaround would be to forward request on to a Lambda function to massage the parameters into the expected shape
I'm a newbie rails programmer, and I have even less experience with all the AWS products. I'm trying to use lambda to subscribe to and consume an rss feed from youtube. I am able to send the subscription request just fine with HTTParty from my locally hosted rails app:
query = {'hub.mode':'subscribe', 'hub.verify':'sync', 'hub.topic': 'https://www.youtube.com/feeds/videos.xml?channel_id=CHANNELID', 'hub.callback':'API Endpoint for Lambda'}
subscribe = 'HTTParty.post(https://pubsubhubbub.appspot.com/subscribe, :query=>query)
and it will ping the lambda function with a get request. I know that I need to echo back a hub.challenge string, but I don't know how. The lambda event is empty, I didn't see anything useful in the context. I tried formatting the response in the API gateway but that didn't work either. So right now when I try to subscribe I get back a 'Challenge Mismatch' error.
I know this: https://pubsubhubbub.googlecode.come/git/pubsubhubbub-core-0.3.html#subscribing explains what I'm trying to do better than what I just did, and section 6.2.1 is where the breakdown is. How do I set up either the AWS Lambda function and/or the API Gateway to reflect back the 'hub.challenge' verification token string?
You need to use the parameter mapping functionality of API Gateway to map the parameters from the incoming query string to a parameter passed to your Lambda function. From the documentation link you provided, it looks like you'll at least need to map the hub.challenge query string parameter, but you may also need the other parameters (hub.mode, hub.topic, and hub.verify_token) depending on what validation logic (if any) that you're implementing.
The first step is to declare your query string parameters in the method request page. Once you have declared the parameters open the integration request page (where you specify which Lambda function API Gateway should call) and use the "+" icon to add a new template. In the template you will have to specify a content type (application/json), and then the body you want to send to Lambda. You can read both query string and header parameters using the params() function. In that input mapping field you are creating the event body that is posted to AWS Lambda. For example: { "challenge": "$input.params('hub.challenge')" }
Documentation for mapping query string parameters
I followed the example from here to set up a sample AWS Lambda function: http://docs.aws.amazon.com/lambda/latest/dg/get-started-step4-optional.html.
Then, I created an HTTP GET endpoint via AWS API Gateway. I can access the endpoint but I don't know how to pass that int myCount as a parameter.
I tried ?myCount=3 as a GET parameter but that didn't work.
Any help?
You need to setup a mapping template in API Gateway. If you know the name of your parameters ahead of time your template could look like this:
{
"myCount": "$input.params('myCount')",
"myUserId": "$input.params('myUserId')"
}
Where each $input.params('...') will get evaluated and the value in your query string will be put in its place when the event is passed to Lambda.
This is pretty much a duplicate of passing query params for aws lambda function
In order to send HTTP parameters to a lambda function, they need to be sent in the request body via a mapping template.
See this blog post for a simple example of how to do this.
This is another way to do it:
Open API Gateway, select your endpoint and click on Resources
Select Method Request in the settings
Under the URL Query String Parameters, you can add query string.
As an example, in my Python lambda function, I can retrieve the query parameter just with the following:
def endpoint(event, context):
my_parameter = event["queryStringParameters"]