Working around AWS Step Function Map concurrency limit - amazon-web-services

I have a Map task in an AWS Step Function which executes 100-200 lambdas in parallel, each running for a few minutes, then collects the results. However, I'm running into throttling where not all lambdas are started for some time. The relevant AWS documentation says you may experience throttling with more than ~40 items, which is what I believe I'm running into.
Does anyone have any experience with working around this concurrency limitation? Can i have nested Maps, or could I bucket my tasks into several Maps I run in parallel?

Use nested state machine inside your map state, so you can have ~40 child state machines executing in parallel. Then inside each child state machine use a map state to process ~40 items in parallel.
This way you can reach processing ~1600 items in parallel.
But before reaching that you will reach AWS Step Functions Quotas:
https://docs.aws.amazon.com/step-functions/latest/dg/limits.html

I ended up working around this 40 item limit by creating 10 copies of the Map task in a Parallel, and bucketing up the task information to split tasks between these 10 copies. This means I can now run ~400 tasks before running into throttling issues. My state machine looks something like this:

AWS now offers a direct solution to this, called "distributed map state", announced at re:invent 2022 https://docs.aws.amazon.com/step-functions/latest/dg/concepts-asl-use-map-state-distributed.html
It allows you to perform 10,000 concurrent map state tasks. Under the hood, it runs them as child step function workflows, which can be specified to run as either standard or express workflows

Related

Solution for two-node nestjs cron service

I have a nestjs cron service that is deployed to two nodes in uat/production.
If i have record that is scheduled to be created at 3 pm, both nodes will fire off at the same time, resulting in a duplicate record in the db.
I am unable to use redis as it would cost money to provision.
I have considered locking the table as well.
Anyone have ideas on how i can solve this issue?
Thank you!
Ideally the way would be to create a lock in shared memory and run only when lock is acquired.
You can replicate the behaviour using the DB. Create a table that stored a lock and allow the cron job to fire only if they are able to acquire the lock else skip. This method would be alright if you're okay with any of the two to execute the job.
If you want to implement a round robin like execution, you can use the lock along with an ID of the previous service which executed, and grant the lock to another ID. But you'll have to ensure there is more than one ID.
If you are fixed on two nodes, a very simple approach would be to displace the first run of the execution by 3 hours, and let each instance run the cron job once in 6 hours.
You may look into the different ways concurrency is handled at an OS level and implement it.

Suppress mesage-The Mapping task failed to run. Another instance of the task is currently running

I have set up multiple jobs in Informatica cloud to sync data from Oracle with Informatica objects. The job is scheduled to run every 3 minutes as per the business requirements. Sometimes the job used to run long due to secure agent resource crunch and my team used to multiple emails as below
The Mapping task failed to run. Another instance of the task is currently running.
Is there any way to suppress these failure emails in the mapping?
This wont get set at the mapping level but on the session or integration service level see following https://network.informatica.com/thread/7312
This type of error comes when workflow/session is running and trying to re-run. use check if by script if already running then wait. If want to run multiple instance of same:
In Workflow Properties Enable 'Configure Concurrent Execution' by checking the check box.
once its enables you 2 options
Allow Concurrent Run with same instance name
Allow Concurrent run only with unique instance name
Notifications configured at the task level over ride those at the org level, so you could do this by configuring notifications at the task level and only sending out warnings to the broader list. That said, some people should still be receiving the error level warning because if it recurs multiple times within a short period of time there may be another issue.
Another thought is that batch processes that run every three minutes that take longer than three minutes is usually an opportunity to improve the design. Often a business requirement for short batch intervals is around a "near real time" desire. If you have also Cloud Application Integration service, you may want to set up an event to trigger the batch run. If there is still overlap based on events, you can use the Cloud Data Integration API to and create a dynamic version of the task each time. For really simple integrations you could perform the integration in CAI, which does allow multiple instances running at the same time.
HTH

Suitability of app with long running tasks for AWS Lambda or AWS Step Functions

I have an application on an AWS EC2 instance that runs once daily. The application fetches some files from a web service, parses the files line by line, updates a database, updates S3 files based on changes in the database, sends notification emails to customers as well as a few other tasks.
This is a series of logical tasks that must take place in sequence, although some of the tasks can be thought of as sub-tasks that can be executed in parallel. All tasks are a combination of Perl scripts and Java programs, with a single Perl script acting as the manager that executes each in turn. Some tasks can take as long as 45 minutes to complete, and the whole process can take up to 3 hours in total.
I'd like to make this whole process serverless. My initial idea was to use AWS Lambda, whereby each task would execute as a Lambda function, until I discovered Lambda functions impose a 5 minute execution timeout. It seems like the AWS Step Functions service is actually a better fit for my use case, but my understanding is that this service is backed by Lambda, so the tasks will still have the 5 min execution limitation.
(I'm also aware that I would have to re-write my Perl scripts to a language supported by Lambda).
I assume that I can work around the execution time limit by refactoring my code into smaller functions that will guarantee to complete in under 5 minutes. In my particular situation though, this seems inefficient.
Currently the database update task processes lines from a file one at a time. For this to work with Lambda, a Lambda function would need to handle only a single line from the file (or a very small number of lines) in order to guarantee not spilling over 5 minutes execution time. This would involve opening and closing a connection with the database on every invocation of the Lambda function. Also, each line processed should result in an entry written to a file, to be stored in S3. Right now, I just keep a file handle in memory and write the file to S3 when all lines are processed, but with Lambda I would need to keep reading the file, updating it and writing it back to S3.
What I'm asking is:
Is my use case a bad fit for AWS Lambda and/or AWS Step Functions?
Have I misunderstood how these services work?
Is there another AWS service that would be a better fit for my use case?
After further research, I think AWS Batch might be a good idea.
What you want are called Activity Workers. Tl;dr: You register "activities" and each gets an ARN. Then you can put that ARN in the resource field of Task states and then you run some code (the "worker") somewhere (in a Lambda, on EC2, in your basement, wherever) that polls for tasks identified by that ARN, then calls back to report success or failure. Activity Workers can run for up to a year.
Step-by-step details at the AWS docs
In response to RTF's comment, here's a deeper dive: Suppose you have code to color turtles in color_turtles.pl. So what you do is call the CreateActivity API - see http://docs.aws.amazon.com/step-functions/latest/apireference/API_CreateActivity.html - giving the name "ColorTurtles" and it'll give you back an ARN, a string beginning arn:aws... Then in your state machine you make a Task state with that ARN as the value of the resource field. Then you add code to color_turtles.pl to poll the service with http://docs.aws.amazon.com/step-functions/latest/apireference/API_GetActivityTask.html - whenever a machine you're running gets to that task, it'll go look for activity workers polling. It'll give your polling worker the input for the task, then you process the input and generate some output, and call SendTaskSuccess or SendTaskFailure. All these are just REST HTTP calls, so you can run them anywhere and I mean anywhere; in a Lambda, on an EC2 instance, or on some computer anywhere on the Internet.
So to answer your questions:
1) Yeah, if you've got something that'll run for around 45 minutes, whilst you could engineer it with Lambda/Step functions you're probably better off getting a EC2 micro instance.
2)Nope you've pretty much got it.
3) As above you want to go with EC2 for this, there's a good article on using Data Pipelines to start / stop an EC2 instance here that way by starting instance only when you need it the cost(if any) is negligible.
I have jobs that run in this fashion normally you can get away with with a t2.micro instance which is free tier eligible.
You can also run your perl scripts on an EC2 instance so no need to rewrite them!
I will start with that it seems you are looking for workflow solutions on AWS. SWF and Step functions are the two most popular ones. Steps function is more recent offering and encouraged by AWS more than SWF.
SWF has native capability to handle long-running tasks, the downside is that you have to provide your own execution environment for deciders (can't use lambda).
With step functions, you can do this in two different ways. One of the approaches is suggested by Tim in his answer. There is an alternative way to achieve the same which is using job poller in step functions. Job pollers have the ability to call (poll) your resource and find out if the task is done and if not you can send execution in wait mode for the specified time. As mentioned above maximum execution time allowed currently for any workflow is 1 year. In case you have tasks which may take longer than 1 year, you can't use step functions in its current form.

Running application on a cluster

Abstract
I have my processing done using two console applications (Stage-estimate, Stage-step), each application processes files on disk, files are organized into folders. Each folder represents one step of processing which is considered completed when all files are estimated.
As an example lets consider that we are at Step 0 and the folder 0 contains the following files:
Folder 0 contains:
000.data
001.data
002.data
...
999.data
We have the data files, now we need to estimate them, we run Stage-estimate application 1000 times that result with the following directory structure:
Folder 0 contains:
000.data
000.estimate
001.data
001.estimate
002.data
002.estimate
...
999.data
999.estimate
Step 0 is now complete we have all the data/estimate pairs. In order to switch to Step 1 we run Stage-step application 1000 times on every data/estimate pair files and it results with new set of 1000 *.data files into folder 1. After Stage-step application completed, we have a folder 1 with the same structure as we had on Step 0:
Folder 1 contains:
000.data
001.data
002.data
...
999.data
From now on the process repeats until it is canceled.
The Problem
Application Stage-estimate does some pretty heavy calculations it consumes 99% of overall processing power compared to Stage-step application.
I was planing to use AWS in order to speed the things up. I don't want to start inventing special batch files that would call my applications the way described above, I know that there is special software that does some high-lifting at scheduling processes and other cluster related stuff.
Question
I was never dealing with cluster computing, off top of my head I see that application is parallelized really nice and it fits into AWS infrastructure. On the other hand I'm complete newbie in the world of cluster-computing and I don't know where to start from. I was dealing with AWS however nothing related to cluster computing, I don't know how to organize the flow I've described and how to make it run efficiently, so I would appreciate if you point me in right direction or provide some links on demos / best practices.
Thank you in advance!
__________Edit__________
Based on your comment, you can put all your jobs from stage 0 into a queue and start to process it. You can also have a logic what checks if you have only a few jobs left and tries to add new jobs from stage 1. This would speed up a bit your calculation, gives you better resource usage, but it's optional and makes your system more complex.
I suggest you to use SQS ( Or SWF) for storing the jobs, S3 for storing the files and an autoscaling group of spot instances for worker nodes.
Unfortunately Lambda doesn't support C++ at the moment. ( Node.js and Java is supported.)
________Original________
AWS supports several concepts which you may consider:
Decoupling: You can use SQS (Simple Queue Service) for job queuing, which gives you a redundant and fault tolerant job queue. You can have a fleet of worker instances, which are requesting jobs form the queue, running them and if they are finished, deleting the job from the queue. If the instances hangs/crashes during the execution of the job, after the timeout period the job goes back to the queue and an other instance will execute it again.
Other service is the SWF ( Simple Workflow Service). This service internally uses SQS queues, with this service, you may need less script to glue your entire workflow together.
Redundant storage: I would definitely use AWS S3 for storage, because it's cheap and redundant. After the first read, I don't think you need any advanced (file system like) feature. ( for example locking.)
Spot instances: For the worker nodes, I would use Spot instances which are much cheaper. The only issue with them if you need a really fast answer for your task all the time. ( If you generating daily reports, spot instances are perfect solution.)
+1: You may use AWS Lambda function to run your jobs. You can trigger your lambda function based on S3 events. For example you uploaded a new *.data file. However Lambda functions cannot run too long. But if you are able to use lambda function, then all your environment will contains only S3 buckets and lambda function. Both of them are AWS managed service, so your system would be extremely flexible, fault tolerant. I can't say any exact details about pricing, but I assume it would be cheaper then running EC2 instances.
Summary: If you can run your estimations parallel, AWS gives you a lots of power and speed. (for a good money) especially if your load is changing during the day.
A good source: White Paper on ‘Cloud Architectures’ and Best Practices of Amazon S3, EC2, SimpleDB, SQS

Are there any Schedulers for AWS/DynamoDB?

We're trying to move to AWS and to use DynamoDB. It'd be nice to keep everything under DynamoDB so there aren't extraneous types of databases, but aside from half complete research projects I'm not really finding anything to use for a scheduler. There's going to be dynamically set schedules in the range of thousands+, possibly with many running at the same time. For languages, Java or at least JVM would be awesome.
Does anyone know a good Scheduler for DynamoDB or other AWS technology?
---Addendum
When I say scheduler I'm thinking of something all purpose like quartz. I want to set a cron and it runs at that time with the code I give it. This isn't doing some AWS task, this is a task internal to our product. SWF's cron runs inside the VM, so I'm worried what happens when the VM is down. Data Pipeline seems a bit too much. I've been looking into making a dynamodb job store for quartz, consistent read might get around the transaction and consistency issues, but I'm hesitant, might be biting off a lot with a lot of hard to notice problems.
Have you looked at AWS Simple Workflow? You would use the AWS Flow Framework to program against the service, and they have a well documented Java API with lots of samples. They support continuous workflows with timers which you can use to run periodic code (see code example here). I'm using SWF and the Flow Framework for Ruby to run async code that gets kicked off from my main app, and it's been working great.
Another new option for you is to look at AWS Lambda. You can attach your Lambda function code directly to a DynamoDB table update event, and Lambda will spin up and shut down the compute resources for you, without you having to manage a server to run your code. Also, recently, AWS launched the ability to call the Lambda function directly -- e.g. you could have an external timer or other code that triggers the function on a specific schedule.
Lastly, this SO thread may have other options for you to consider.
Another option is to use AWS Lambda Scheduled Functions (newly announced on October 8th 2015 at AWS re:Invent).
Here is a relevant snippet from the blog (source):
Scheduled Functions (Cron)
You can now invoke a Lambda function on a regular, scheduled basis. You can specify a fixed rate (number of minutes, hours, or days between invocations) or you can specify a Cron-like expression: