I have a AWS Lambda function running some process in my infrastructure. The Lambda is triggered every 8 hours using a CloudWatch rule. I am trying to raise a notification if any error happens into the Lambda process. I tried to use SES but that service is not available in that Region.
I will like to know any suggestions for this problem:
How to setup notifications when an error occurs in my Lambda functions ?
I am looking for suggestions. This questions never asked for doing my task. I will appreciate any official documentation but either way, any help is welcome.
Some suggestions:
Dead Letter Queues:
If your error causes failed invocations, you can use a Lambda Dead Letter Queue to send the event to an SNS topic or an SQS queue. If you send it to an SNS topic, you can directly subscribe to the topic via SNS or Email to get notified any time a message is published to that topic.
Multi-region SES:
If you're really set on using SES directly, SES clients can be instantiated with an explicit region provided -- as long as your lambda's execution role has the appropriate permissions, you can send email to SES from a different region. Here's documentation for instantiating the JS SES Client.
CloudWatch Logs:
If your error does not cause the invocation to fail, another option is using a CloudWatch Logs metric filter to aggregate failures and potentially alarm on them. If you're using NodeJS, you can simply log out via console.log(), console.error(), etc. and it will be written out to CWLogs. More details here.
You can subscribe an SNS topic to CloudWatch Alarms, and notify yourself in the same way as the DLQ.
As you gain experience with the error and learn how to process common errors, you could also subscribe another lambda to the SNS topic from the DLQ/CWLogs example to process it as it happens.
Related
I have a cloudWatch alert setup on all lambdas sending data to a an SNS topic
Using the metric as
sum(errors) across all functions
I get the notification as expected, but there is no information in there to identify which amongst my lambdas triggered the alarm or in other words which one failed
If I setup the alarm individually on each lambda, then I get the information on which one failed under Dimensions. But I have a lot of them and plan to add more and this process will become painful
How can I leverage cloudWatch to alert me on all lambda failures and also provide info on which lambda failed and the error message ?
Should this be implemented in a different way ?
The AWS Cloud Operations & Migrations Blog has a post published on this topic.
Instead of using CloudWatch Alarms as you are doing now, you can use a CloudWatch Logs subscription. Whenever a log entry matches a specific pattern that you specify, it will trigger a new Lambda function that can notify you however you choose. In the blog post, the Lambda uses SNS to send an email notification.
You can control what information gets included in the body of the notification by adjusting what the Lambda function sends to SNS. The log group name, log stream, and the error message itself can be included.
I have a topic at AWS SNS which sends messages to an AWS Lambda function. This function may sometimes fail and depending on which attempt is currently running I need to store some information about the failure. After looking for a while I didn't find any way to do that. Is it possible to retrieve which attempt is running?
I tried to use the delivery status feature and retrieve the attempt number using CloudWatch Events, but apparently SNS always deliver successfully its notifications to Lambda functions.
When a Lambda function fails it retries like explained here and not using delivery polices defined at the SNS topic (because it was delivered successfully).
In this particular case I guess it must be implemented mannually.
I want to trigger Lambda function whenever new message added to SQS.
Note that I don't want to add new message (events) to SQS.
What I'm trying to do:
My app will send message to SQS
Whenever new message added to queue CloudWatch event gets generated
CloudWatch Event triggers lambda
Problem:
In AWS console while configuring CloudWatch Events I haven't found any option to add source of event i.e. URL or Name of my SQS queue.
I'm not sure if this use case is valid but please help me out.
EDIT: AWS now supports SQS as an event source to trigger Lambda functions. See this blog post for more details.
ORIGINAL ANSWER:
SQS is not supported as a direct event source for AWS Lambda functions. If there are properties of a queueing system that you need for your use case, then you could have a "cron-job" type Lambda function that runs on a schedule, receives messages from the queue, and calls your worker Lambda function in response to each message received. The problem with this approach is that you must continually poll SQS even during periods when you don't expect messages, which incurs unnecessary cost.
The easiest approach is to use SNS instead. Create a topic, publish events to that topic instead of adding a message to an SQS queue, and have your Lambda function subscribe to that SNS topic. It will then be invoked each time a message is published to that SNS topic. There's a tutorial on this approach here:
http://docs.aws.amazon.com/lambda/latest/dg/with-sns-example.html
I would recommend to change your approach.
Your application should publish a message to an existing SNS topic. Your SQS and Lambda should than subscribe to this SNS topic.
Application -> publish -> SNS_TOPIC
-> SQS is notified
-> Lambda is notified
I have the following infrastructure:
I have an EC2 instance with a NodeJS+Express process listening on a port for messages (process 1). Every time the process receives a message it sends it to an SQS queue. Then I have another process in the same machine reading the queue using long polling (process 2). When it finds a message in the queue it inserts the data in a MariaDB database sitting on an RDS instance.
(Just to clarify, messages are generated by users, they send a chunk of data which can contain arbitrary information to the endpoint where the process 1 is listening)
Now I want to put the process that reads the SQS (process 2) in a Lambda function so that the process that writes to the queue and the one that reads from the queue are completely independent. The problem is that I don't know if this is possible.
I know that Lambda function are invoked in response to an event, and the events supported at the moment are S3, SNS, SES, DynamoDB, Kinesis, Cognito, CloudWatch and Cloudformation but NOT SQS.
I was thinking in using SNS notifications to invoke the Lambda function so that every time a message is pushed to the queue, an SNS notification is fired and invokes the Lambda function but after playing a bit with it I've realised that is not possible to create an SNS notification from SQS, it's only possible to write SNS notifications to the queue.
Right now I'm a bit stuck because I don't know how to continue. I have the feeling that is not possible to create this infrastructure due to the current limitations in the AWS services. Is there another way to do what I want or am I in a dead-end?
Just to extend my question with some research I've made, this github repo shows how to read an SQS queu from a Lambda function but the lambda function works only if is fired from the command line:
https://github.com/robinjmurphy/sqs-to-lambda
In the readme, the author mentions the following:
Update: Lambda now supports SNS notifications as an event source,
which makes this hack entirely unneccessary for SNS notifcations. You
might still find it useful if you like the idea of using a Lambda
function to process jobs on an SQS queue.
But I think this doesn't solve my problem, an SNS notification can invoke the Lambda function but I don't see how I can create a notification when a message is received in the SQS queue.
Thanks
There are couple of Strategies which can be used to connect the dots, (A)Synchronously or Run-Sleep-Run to keep the data process flow between SNS, SQS, Lambda.
Strategy 1 : Have a Lambda function listen to SNS and process it in real time [Please note that an SQS Queue can subscribe to an SNS Topic - which would may be helpful for logging / auditing / retry handling]
Strategy 2 : Given that you are getting data sourced to SQS Queue. You can try with 2 Lambda Functions [Feeder & Worker].
Feeder would be scheduled lambda function whose job is to take items
from SQS (if any) and push it as an SNS topic (and continue doing it forever)
Worker would be linked to listen the SNS topic which would do the actual data processing
We can now use SQS messages to trigger AWS Lambda Functions. Moreover, no longer required to run a message polling service or create an SQS to SNS mapping.
Further details:
https://aws.amazon.com/blogs/aws/aws-lambda-adds-amazon-simple-queue-service-to-supported-event-sources/
AWS SQS is one of the oldest products of Amazon, which only supported polling (long and short) up until June 2018. As mentioned in this answer, AWS SQS now supports the feature of triggering lambda functions on new message arrival in SQS. A complete tutorial for this is provided in this document.
I used to tackle this problem using different mechanisms, and given below are some approaches you can use.
You can develop a simple polling application in Lambda, and use AWS CloudWatch to invoke it every 5 mins or so. You can make this near real-time by using CloudWatch events to invoke lambda with short downtimes. Use this tutorial or this tutorial for this purpose. (This could cost more on Lambdas)
You can consider that SQS is redundant if you don't need to persist the messages nor guarantee the order of delivery. You can use AWS SNS (Simple Notification Service) to directly invoke a lambda function and do whatever the processing required. Use this tutorial for this purpose. This will happen in real-time. But the main drawback is the number of lambdas that can be initiated per region at a given time. Please read this and understand the limitation before following this approach. Nevertheless AWS SNS Guarantees the order of delivery. Also SNS can directly call an HTTP endpoint and store the message in your DB.
I had a similar situation (and now have a working solution deploed). I have addressed it in a following manner:
i.e. publishing events to SNS; which then get fanned-out to Lambda and SQS.
NOTE: This is not applicable to the events that have to be processed in a certain order.
That there are some gotchas (w/ possible solutions) such as:
racing condition: lambda might get invoked before messages is deposited into the queue
distributed nature of SQS queue may lead to returning no messages even though there is a message note1.
The solution to both cases would be to do long-polling of SQS queue; but this does make your lambda bill more expensive.
note1
Short poll is the default behavior where a weighted random set of machines is sampled on a ReceiveMessage call. This means only the messages on the sampled machines are returned. If the number of messages in the queue is small (less than 1000), it is likely you will get fewer messages than you requested per ReceiveMessage call. If the number of messages in the queue is extremely small, you might not receive any messages in a particular ReceiveMessage response; in which case you should repeat the request.
http://docs.aws.amazon.com/AWSSimpleQueueService/latest/APIReference/API_ReceiveMessage.html
We had some similar requirements so we ended up building a library and open sourcing it to help with SQS to Lambda async. I'm not sure if this fills your particular set of requirements, but thought it might be worth a look: https://read.iopipe.com/sqs-lambda-teaming-up-92c4096be49c
My system run on an Amazon autoscaling group and one feature allows user to user messaging and I have the following use case to resolve.
A new message is sent in my application between users.
A message to notify the the user by e-mail is dropped into a queue with a 60 second delay. This delay allows time for a realtime chat client (faye/angularjs) to see the message and mark it as viewed.
After the delay the message is picked up, the "read" status is checked and if it has not been read by the client an e-mail is dispatched.
Originally I was going to use a cronjob on each application server poll the message queue however it occurs to me it would be more efficient to use SNS to call some kind of e-mail sending endpoint (perhaps in Lambda).
I can't see any way to have SNS poll SQS however, can anybody suggest how this could be done? Essentially I want SNS with a delay so that I don't spam somebody in a "live" chat with e-mail alerts.
Thanks
Unfortunately this is not yet available out of the box. The missing part is the generation of Amazon SNS notifications on message arrival/visibility by an Amazon SQS queue, be it via push (similar to Amazon S3 notifications, or via poll similar to Amazon Kinesis subscriptions (see The Pull/Push Event Models for more on the difference), which would both allow to directly connect an AWS Lambda function to the resp. SQS delay queue events, see e.g.:
Lambda with SQS
That being said, you can work around this limitations in a few ways, for example:
trigger your Lambda function on schedule (e.g. once per minute), and poll your SQS delay queue from there
scheduled Lambda functions are an eagerly awaited missing Lambda feature in turn, but it is more easily worked around, be it either by a cron job of yours, or Eric Hammond's Unreliable Town Clock (UTC) for example
The AWS Lambda team has delivered many/most similar feature requests over recent month' btw., so I would expect them to offer both SQS event handling and scheduled Lambda functions over the course of the year still.
In early 2019, this problem can be solved in a few different ways:
SQS as an Event Source to Lambda (finally announced 2018-06-28),
similar to the OP's original design.
AWS Step Functions (announced 2016-12-01), using a wait step for
the delay.
DynamoDB Streams with Lambda triggers (announced 2017-02-17),
using TTL expiration on items to fire the Lambda trigger.
As SNS has a topic limit of 100,000 per account, I would recommend using Amazon SES to send the emails (62,000 free emails/month could help with implementation cost decisions).