Ordering Messages In An Amazon SQS Queue

Last November, AWS released a very useful feature in its FIFO support for Amazon Simple Queue Service (SQS). FIFO stands for “first in first out”, which essentially means that a FIFO queue maintains the order of how messages are delivered out of an SQS queue. The FIFO queue feature also guarantees on-time delivery of a message, which is a pretty big deal if you’ve had to design systems where on-time delivery was a “must have” feature.

Prior to having FIFO queue support for SQS, the random order of SQS messages was not a deal breaker but any ordering needed to be handled outside of SQS. You could create your own ordering key and parse it in the message attributes. Features such as the message timeout window and dead letter queues helped manage the issue of message duplication if needed. This approach didn’t always suit if you needed to implement a queue where the order and frequency of messages were mission critical.

Enter First In First Out queue support for Amazon SQS in US West and US East.

How FIFO for Amazon SQS works

You interact with a FIFO SQS queue the same way that you interact with a standard SQS queue. With a FIFO queue, however, the order in which messages are sent and received is strictly preserved. A message is delivered once and remains available until a consumer processes and deletes it. This means that duplicates will not be created in the queue. This is pretty cool, so let’s take a look at how we can use it.

An SQS queue is recognized as a FIFO queue if it has the FifoQueue attribute set to true and the queue name ends with the .fifo suffix. FIFO queues use the same API actions as standard queues.

// A FIFO queue must have the FifoQueue attribute set to True
attributes.put("FifoQueue", "true");
// A FIFO queue name must end with the .fifo suffix
CreateQueueRequest createQueueRequest = new CreateQueueRequest("MyFifoQueue.fifo").withAttributes(attributes);
String myQueueUrl = sqs.createQueue(createQueueRequest).getQueueUrl();

The methods for receiving messages, deleting messages, and changing the visibility timeout are the same as for a standard SQS queue. However, when you send a message from a FIFO queue you must specify a message group ID.
Every message sent to a FIFO queue requires a MessageGroupId value. If you don’t add a MessageGroupId value, the send action fails.

// You must provide a MessageGroupId
sendMessageRequest.setMessageGroupId("1");

How Amazon SQS uses MessageGroupId

Amazon SQS uses the MessageGroupId value to group messages together. Messages within a group are ordered within that group. So if we add a MessageGroupId=1 value to 10 messages, those 10 messages are treated as a message group and will be processed one by one, in a strict order relative to the group MessageGroupId=1. If we send another five messages with a new MessageGroupId=2, those five messages will be ordered within the group MessageGroupId=2.

That means we can have multiple ordered message groups within a single queue. So, our 10 messages in MessageGroupId=1 and our five messages in MessageGroupId=2 will be processed in order relative to each group rather than to the queue as a whole. As ordering only applies to the message group, messages that belong to a different message group might be processed in the same order.

If you have a system that will have multiple senders and multiple recipients, you should generate a unique MessageGroupId for each message. If you don’t need to create multiple ordered message groups, just use the same MessageGroupId for all of your messages.

If your SendMessage action fails, you can retry sending as many times as you want using the same message deduplication ID. Assuming that you receive at least one acknowledgment before the deduplication interval expires (the minimum deduplication window is five minutes), multiple retries will not affect the ordering of messages or create duplications.

When you receive messages, SQS will try to return as many messages with the same MessageGroupId as possible. However, you can’t request to receive messages with a specific MessageGroupId. If you get a failed ReceiveMessage action, you can retry using the same receive request attempt ID. Assuming that you receive at least one acknowledgment before the visibility timeout expires, multiple retries will not affect the ordering of messages.

A FIFO message uses a MessageDeduplicationId key to manage deduplication of sent messages. Every message must have a unique MessageDeduplicationId. If a message with a particular MessageDeduplicationId is sent successfully, any messages sent with the same MessageDeduplicationId will not be delivered during the five-minute deduplication window.

So, if you send 10 messages in succession to a FIFO queue, each with a distinct MessageDeduplicationId, SQS acknowledges the transmission and stores those messages. Then, each message can be received and processed in the exact order in which the messages were transmitted.

How to create a MessageDeduplicationId

There are two ways to create a MessageDeduplicationId. First, you can define your own MessageDeduplicationId for the message. If your application sends messages with identical message bodies, you can modify your code to provide a unique message MessageDeduplicationId for each sent message.

// define a MessageDeduplicationId
sendMessageRequest.setMessageDeduplicationId("1");

Second, you can just enable content-based deduplication. This tells SQS to use an SHA-256 hash to generate the MessageDeduplicationId using the body of the message. If your application sends messages with unique message bodies, then enabling content-based deduplication will be easiest.

// Generate a MessageDeduplicationId based on the content
attributes.put("ContentBasedDeduplication", "true");

Is a FIFO SQS for you?

Here are five things to keep in mind when considering if a FIFO SQS queue suits your use case.

1. Conversions. You can’t convert an existing standard queue into a FIFO queue. You need to delete your standard queue and then create a new FIFO queue.
2. Transaction rate. FIFO queues are limited to 300 transactions per second (TPS). If your application needs a higher rate than 300 TPS, stick to a standard SQS queue.
3. Delays. FIFO queues support per queue delays but not per message delays. If your application sets a DelaySeconds = 10 on each message, that’s probably not going to work with a FIFO queue. You will need to remove any per message parameter and set a DelaySeconds =10 parameter on the entire queue.
4. Processing time. You need to ensure that there is enough time to process and delete a message. Extend your message visibility timeout to the maximum time it takes to process and delete the message. If you don’t know how long it takes to process a message, specify the initial visibility timeout plus the period of time after which you can check whether the message is processed. If it’s taking a long time to process messages and your visibility timeout is already set to a high value, consider adding a receive request attempt ID to each ReceiveMessage action. This allows you to retry receive attempts in case of network failures and prevents queues from pausing due to failed receive attempts.
5. Inflight message limit. While Amazon SQS queues can include an unlimited number of messages, there is a 20,000 inflight message limit for inflight FIFO queues (The inflight message limit for standard SQS queues is 120,000.). Messages are inflight after they have been received from the queue by a consumer, but have not yet been deleted from the queue.

Learning more about FIFO SQS

Hopefully, I have piqued your interest in this great new feature. There is a lot more to know about SQS FIFO, so if you are interested, I suggest starting with the AWS developer guide and API reference. If you have any questions or content you’d like to add, please leave a comment right here below this post.

Avatar

Written by

Andrew Larkin

Andrew is an AWS certified professional who is passionate about helping others learn how to use and gain benefit from AWS technologies. Andrew has worked for AWS and for AWS technology partners Ooyala and Adobe. His favorite Amazon leadership principle is "Customer Obsession" as everything AWS starts with the customer. Passions around work are cycling and surfing, and having a laugh about the lessons learnt trying to launch two daughters and a few start ups.

Related Posts

Avatar
Michael Sheehy
— August 19, 2019

What Exactly Is a Cloud Architect and How Do You Become One?

One of the buzzwords surrounding the cloud that I'm sure you've heard is "Cloud Architect." In this article, I will outline my understanding of what a cloud architect does and I'll analyze the skills and certifications necessary to become one. I will also list some of the types of jobs ...

Read more
  • AWS
  • Cloud Computing
Avatar
Andrew Larkin
— August 13, 2019

Content Roadmap: AZ-500, ITIL 4, MS-100, Google Cloud Associate Engineer, and More

Last month, Cloud Academy joined forces with QA, the UK’s largest B2B skills provider, and it put us in an excellent position to solve a massive skills gap problem. As a result of this collaboration, you will see our training library grow with additions from QA’s massive catalog of 500+...

Read more
  • AWS
  • Azure
  • content roadmap
  • Google Cloud Platform
Avatar
Adam Hawkins
— August 9, 2019

DevSecOps: How to Secure DevOps Environments

Security has been a friction point when discussing DevOps. This stems from the assumption that DevOps teams move too fast to handle security concerns. This makes sense if Information Security (InfoSec) is separate from the DevOps value stream, or if development velocity exceeds the band...

Read more
  • AWS
  • cloud security
  • DevOps
  • DevSecOps
  • Security
Avatar
Stefano Giacone
— August 8, 2019

Test Your Cloud Knowledge on AWS, Azure, or Google Cloud Platform

Cloud skills are in demand | In today's digital era, employers are constantly seeking skilled professionals with working knowledge of AWS, Azure, and Google Cloud Platform. According to the 2019 Trends in Cloud Transformation report by 451 Research: Business and IT transformations re...

Read more
  • AWS
  • Cloud skills
  • Google Cloud
  • Microsoft Azure
Avatar
Andrew Larkin
— August 7, 2019

Disadvantages of Cloud Computing

If you want to deliver digital services of any kind, you’ll need to estimate all types of resources, not the least of which are CPU, memory, storage, and network connectivity. Which resources you choose for your delivery —  cloud-based or local — is up to you. But you’ll definitely want...

Read more
  • AWS
  • Azure
  • Cloud Computing
  • Google Cloud Platform
Joe Nemer
Joe Nemer
— August 6, 2019

Google Cloud vs AWS: A Comparison (or can they be compared?)

The "Google Cloud vs AWS" argument used to be a common discussion among our members, but is this still really a thing? You may already know that there are three major players in the public cloud platforms arena: Amazon Web Services (AWS), Microsoft Azure, and Google Cloud Platform (GCP)...

Read more
  • AWS
  • Google Cloud Platform
  • Kubernetes
Avatar
Stuart Scott
— July 29, 2019

Deployment Orchestration with AWS Elastic Beanstalk

If you're responsible for the development and deployment of web applications within your AWS environment for your organization, then it's likely you've heard of AWS Elastic Beanstalk. If you are new to this service, or simply need to know a bit more about the service and the benefits th...

Read more
  • AWS
  • elastic beanstalk
Avatar
Stuart Scott
— July 26, 2019

How to Use & Install the AWS CLI

What is the AWS CLI? | The AWS Command Line Interface (CLI) is for managing your AWS services from a terminal session on your own client, allowing you to control and configure multiple AWS services and implement a level of automation. If you’ve been using AWS for some time and feel...

Read more
  • AWS
  • AWS CLI
  • Command line interface
Alisha Reyes
Alisha Reyes
— July 22, 2019

Cloud Academy’s Blog Digest: July 2019

July has been a very exciting month for us at Cloud Academy. On July 10, we officially joined forces with QA, the UK’s largest B2B skills provider (read the announcement). Over the coming weeks, you will see additions from QA’s massive catalog of 500+ certification courses and 1500+ ins...

Read more
  • AWS
  • Azure
  • Cloud Academy
  • Cybersecurity
  • DevOps
  • Kubernetes
Avatar
Stuart Scott
— July 18, 2019

AWS Fundamentals: Understanding Compute, Storage, Database, Networking & Security

If you are just starting out on your journey toward mastering AWS cloud computing, then your first stop should be to understand the AWS fundamentals. This will enable you to get a solid foundation to then expand your knowledge across the entire AWS service catalog.   It can be both d...

Read more
  • AWS
  • Compute
  • Database
  • fundamentals
  • networking
  • Security
  • Storage
Avatar
Adam Hawkins
— July 17, 2019

How to Become a DevOps Engineer

The DevOps Handbook introduces DevOps as a framework for improving the process for converting a business hypothesis into a technology-enabled service that delivers value to the customer. This process is called the value stream. Accelerate finds that applying DevOps principles of flow, f...

Read more
  • AWS
  • AWS Certifications
  • DevOps
  • DevOps Foundation Certification
  • Engineer
  • Kubernetes
Avatar
Vineet Badola
— July 15, 2019

AWS AMI Virtualization Types: HVM vs PV (Paravirtual VS Hardware VM)

Amazon Machine Images (AWS AMI) offers two types of virtualization: Paravirtual (PV) and Hardware Virtual Machine (HVM). Each solution offers its own advantages. When we’re using AWS, it’s easy for someone — almost without thinking —  to choose which AMI flavor seems best when spinning...

Read more
  • AWS
  • Hardware Virtual Machine
  • Paravirtual
  • Virtualization