I have an aws lambda function which runs some python code (which is calling an external api with some extra functions). I attached a trigger, an api gateway, which if I go to the url, the lambda functions runs correctly.
However, I want the lambda function only to be run if they click on a button somewhere on the 'website' of the api-url. Rephrased otherwise, I want the api-url page to have a button, which on click executes the lambda function.
Im think that should be quite easy, however I can't figure out how. Due to the information overload I can't seem to find the right video, document example on how to do it.
Is the possible? (running the lambda function on click of a button). If so, is there some good documentation of example of this?
I tried to add a button on the api-url page by, on 'method-execution' on the 'api-gateway resource' page, changing the mapping template to text/html instead of json. (a bit like in https://blog.it-playground.eu/display-html-page-using-only-api-gateway/) But then i can't figure out how to run the lambda function onClick of the button. ==> Is this the right start?
(Because its not really a coding issue, I can't really provide any code).
Also, is this question so simply that it shows I simply don't understand the basics enough (and should subsequently go over them again)?
Of course this is possible. API Gateway exposes REST API. All you need to do is to create some resource and method in API Gateway such as
GET /posts
attach your lambda function to it, and hit that API endpoint with some ajax request from your front end (via fetch, axios, ...) that would be executed when the button is clicked. Something like:
button.addEventListener("click", () => {
fetch("https://my-api-gateway-url/posts").then() ...
}
You can process the response data in .then part but don't forget that this is asynchronous coding so you need to handle it as such.
Related
i have a question about lambda anti patterns, and how to address my specific situation.
My current setup is this:
user/webpage -> ApiGateway -> Lambda1 -> synchronously calls Lambda2 (my other microservice) -> back to lambda1 -> back to user
Currently my lambda2 is behind an apigateway as well, but I toyed with idea of invoking directly. Either way it's basically another microservice that I control.
I understand that generally, lambdas calling other lambdas are considered an antipattern. All the blogs/threads/etc online mention using stepfunctions instead, or sqs, or something else.
In my situation, I don't see how I could use stepfunctions, since I have to return something to the webpage/user. If I used a stepfunction, it seems like I would have to then poll for the results, or maybe use websockets; basically in my webpage I would not be able to just call my endpoint and get a result, I'd have to have some way to asynchronously get my result.
Similarly with a queue, or any other solution I saw online, it's basically all asynchronous.
Is there any other pattern or way of doing this?
Thanks.
While invoking a lambda from another lambda, everything will work fine except when the second lambda timeouts or it throttles. If your business logic is built in such a way that failures are handled gracefully and has idempotent behaviour built in, then a lambda calling another lambda (via API gateway or direct invocation) should work fine. Having said that, AWS has come out with Synchronous Express Workflows for AWS Step Functions. The linked blog has detailed examples of using it. The only caveat here is that your entire operation should get over in 5 minutes. The maximum duration an express workflow can run is 5min. So if your application flow is completing within that time limit then this is the recommended way of orchestrating services.
Im a little confused since AWS has a lot of features and I do not know what to use.
So, I was creating a Lambda function that does a lot of stuff with a remote web, process could last at least a minute.
So my idea was creating an API that calls this lambda, have lambda create an unique ID and return a response right away to the client with a token., save this token to a DB.
Then have lambda process all this stuff with a remote web and, when it finishes, save the results to the DB and a bucket (a file), so this result is ready to deliver when the client makes another call to another API that makes a query to the DB to know the status of this process.
Thing is, it seems that if a response is sent from the handler, lambda terminates the execution, Im afraid the processing with the remote web will never finish.
I have read that step functions is the way to go, but I cant figure out which service will take the processing, ¿maybe another lambda?
Is there another service that is more suitable for this type of work?, this process involves scrapping a page and downloading files, is written in python.
I have read that step functions is the way to go, but I cant figure
out which service will take the processing, ¿maybe another lambda?
Yes, another Lambda function would do the background processing. You could also just have the first Lambda invoke a second Lambda directly, without using Step Functions. Or the first Lambda could place the task info in an SQS queue that another Lambda polls.
Is there another service that is more suitable for this type of work?
Lambda functions are fine for this. You just need to split your task into multiple functions somehow, either by one Lambda calling the other directly, or by using Step Functions, or an SQS queue or something.
I have a lambda setup that uses vendia serveless-express as a handler. It has been working well to serve REST APIs from the single lambda function with multiple routes.
I now have a new requirement, where the same lambda needs to be part of a step function's state machine. But that doesn't seem to be allowed by vendia app, as it always throws the error: "Unable to determine event source based on event" as it expects the event to be api gateway / alb only.
So, based on this, it looks like I will need a separate lambda for step, which makes me have duplicate code in multiple lambdas.
Is it possible for the lambda to handle the inputs from step and still be a vendia express app? Please let me know if I am trying something that doesn't make sense at all.
If I were you I would just implement my own converter that transforms a StepFunction event into an API Gateway event and then calling the express-serverless in your lambda.
The package aws-lambda contains definitions in TypeScript of many AWS events including those ones, then try to generate a mock API Gateway event from your own step function event value. From the sources (4.3.9) we have the function:
function getEventSourceNameBasedOnEvent ({
event
}) {
if (event.requestContext && event.requestContext.elb) return 'AWS_ALB'
if (event.Records) return 'AWS_LAMBDA_EDGE'
if (event.requestContext) {
return event.version === '2.0' ? 'AWS_API_GATEWAY_V2' : 'AWS_API_GATEWAY_V1'
}
throw new Error('Unable to determine event source based on event.')
}
So probably to make it work correctly, you have to define a RequestContext mock value in your mock event and it should be enough.
I am using AppSync with Aurora/RDS.
I would like that in some cases, when a query/mutation is sent to the db, then, after that, I want to send an email and push notification, but this should be detached from the query/mutation, that is, it does not matter if it fails or works.
At the moment I see all these options:
Can you tell me which one I should use?
Create a query that calls a lambda function that sends the
push/email and call it from the client once the actual
query/mutation is done. I don't like this because the logic is in
the client rather than the server. Seems easy to implement, and I
guess it is easy to ignore the result of the second operation from a
client point of view.
A variation of the previous one. Pack both operations in a single
network request. With GraphQL, that is easy, but I don't want the
client waits for the second operation. (Is it possible to create
lambda functions that return immediately, like a trigger of other
functions?)
Attach my queries/mutations to lambda functions instead of RDS
directly. Then, those lambda functions call other lambda functions
for notifications. Seems more difficult to program, but more
micro-services architecture friendly. Probably this is the best one,
not sure.
Use SQL triggers and call lambda functions from those triggers. I
don't know if this is even possible. Researching...
Use pipelines resolvers. The first one is the query/mutation, the
second one is the lambda function that sends the push/email. I would
say this is a bad option because I don't want the client to wait for
the second operation or manage the logic when the second resolver
fails.
Amazon RDS Events: It appears it is possible to attach lambda
functions to specific AWS RDS events.
https://docs.aws.amazon.com/lambda/latest/dg/services-rds.html It
seems it is about creating DBs, restoring... and that kind of
things. I don't see anything like creating a row, updating a row...
So, I discard this unless I am wrong.
Invoking a Lambda Function with an Aurora MySQL Stored Procedure
CALL mysql.lambda_async ( lambda_function_ARN,lambda_function_input )
https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/AuroraMySQL.Integrating.Lambda.html
"For example, you might want to send a notification using Amazon
Simple Notification Service (Amazon SNS) whenever a row is inserted
into a specific table in your database." That is exactly what I am
looking for. I like this idea, but I don't know if that is possible
with Aurora Serverless. Researching... It seems it is not possible
when using server-less:
https://www.reddit.com/r/aws/comments/a9szid/aurora_serverless_call_lambda/
Use step functions: No idea about how to use it.
Somehow, attach this lambda notification function to GraphQL/AppSync
instead of the database, but I guess it is not a good idea because I
need to read the database to the push notification token and the
email of the use who is going to receive the notifications.
Which method do you recommend me? I am using amplify cli.
Thanks a lot.
Currently AWS AppSync can only send notifications when the app is active. We are looking into implementation of the non active case.
If you want to send notifications when the app is not active, you can use the push notifications on iOS: silent push/interactive push or push notifications on Android.
If you want to send emails, voice/text message or notifications on phone when the app is not active, you can integrate with Amazon Pinpiont.
My Lex bot has four intents. Suppose a user asks a question at the very beginning of the conversation and this question is not allotted to any of the four intents. Hence no intent will be established. When this happens, I want to call lambda to run an "intent suggestion model" (built using topic modeling) to suggest the user about what the intent of the question might be. Also, lambda will have to store such queries in a database (s3 or RDB) so that if such queries are repetitive, then that intent can eventually be added to the bot and for other analytical solutions.
What you need is a fallback intent but Lex does not support fallback intents as of now.
You can still achieve this if you use a bridge between your chat client and Lex.
Setup an API Gateway and Lambda function in between your chat-client and the Lex.
Your chat-client will send a request to API Gateway, API Gateway will forward this to Lambda function which will be used to call Lex and get response from it. Lex will have one more lambda function as a webhook.
In the Lambda function you used to call Lex, we can check if any intent was matched or we got an error message, if it's an error message and trigger some action like intent suggestion model.
You need to use boto library to call Lex and use post_text() method.
Hope it helps.