Mike  Kozey

Mike Kozey

1639845385

Create a NestJS Redis Microservice

In this post, we'll learn to create a NestJS Redis Microservice using the Redis transporter. This transporter leverages the publish/subscribe messaging paradigm.

In this post, we will learn how to create a NestJS Redis Microservice. Basically, we will learn how to use the Redis transporter. This transporter leverages the publish/subscribe messaging paradigm.

This post uses the NestJS Microservice package. If you are new to the same, please refer to this detailed post about creating a NestJS Microservice.

#microservices 

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Create a NestJS Redis Microservice
Loma  Baumbach

Loma Baumbach

1596679140

Redis Transactions & Long-Running Lua Scripts

Redis offers two mechanisms for handling transactions – MULTI/EXEC based transactions and Lua scripts evaluation. Redis Lua scripting is the recommended approach and is fairly popular in usage.

Our Redis™ customers who have Lua scripts deployed often report this error – “BUSY Redis is busy running a script. You can only call SCRIPT KILL or SHUTDOWN NOSAVE”. In this post, we will explain the Redis transactional property of scripts, what this error is about, and why we must be extra careful about it on Sentinel-managed systems that can failover.

Redis Lua Scripts Diagram - ScaleGrid Blog

Transactional Nature of Redis Lua Scripts

Redis “transactions” aren’t really transactions as understood conventionally – in case of errors, there is no rollback of writes made by the script.

Atomicity” of Redis scripts is guaranteed in the following manner:

  • Once a script begins executing, all other commands/scripts are blocked until the script completes. So, other clients either see the changes made by the script or they don’t. This is because they can only execute either before the script or after the script.
  • However, Redis doesn’t do rollbacks, so on an error within a script, any changes already made by the script will be retained and future commands/scripts will see those partial changes.
  • Since all other clients are blocked while the script executes, it is critical that the script is well-behaved and finishes in time.

The ‘lua-time-limit’ Value

It is highly recommended that the script complete within a time limit. Redis enforces this in a weak manner with the ‘lua-time-limit’ value. This is the maximum allowed time (in ms) that the script is allowed to run. The default value is 5 seconds. This is a really long time for CPU-bound activity (scripts have limited access and can’t run commands that access the disk).

However, the script is not killed when it executes beyond this time. Redis starts accepting client commands again, but responds to them with a BUSY error.

If you must kill the script at this point, there are two options available:

  • SCRIPT KILL command can be used to stop a script that hasn’t yet done any writes.
  • If the script has already performed writes to the server and must still be killed, use the SHUTDOWN NOSAVE to shutdown the server completely.

It is usually better to just wait for the script to complete its operation. The complete information on methods to kill the script execution and related behavior are available in the documentation.

#cloud #database #developer #high availability #howto #redis #scalegrid #lua-time-limit #redis diagram #redis master #redis scripts #redis sentinel #redis servers #redis transactions #sentinel-managed #server failures

Einar  Hintz

Einar Hintz

1599055326

Testing Microservices Applications

The shift towards microservices and modular applications makes testing more important and more challenging at the same time. You have to make sure that the microservices running in containers perform well and as intended, but you can no longer rely on conventional testing strategies to get the job done.

This is where new testing approaches are needed. Testing your microservices applications require the right approach, a suitable set of tools, and immense attention to details. This article will guide you through the process of testing your microservices and talk about the challenges you will have to overcome along the way. Let’s get started, shall we?

A Brave New World

Traditionally, testing a monolith application meant configuring a test environment and setting up all of the application components in a way that matched the production environment. It took time to set up the testing environment, and there were a lot of complexities around the process.

Testing also requires the application to run in full. It is not possible to test monolith apps on a per-component basis, mainly because there is usually a base code that ties everything together, and the app is designed to run as a complete app to work properly.

Microservices running in containers offer one particular advantage: universal compatibility. You don’t have to match the testing environment with the deployment architecture exactly, and you can get away with testing individual components rather than the full app in some situations.

Of course, you will have to embrace the new cloud-native approach across the pipeline. Rather than creating critical dependencies between microservices, you need to treat each one as a semi-independent module.

The only monolith or centralized portion of the application is the database, but this too is an easy challenge to overcome. As long as you have a persistent database running on your test environment, you can perform tests at any time.

Keep in mind that there are additional things to focus on when testing microservices.

  • Microservices rely on network communications to talk to each other, so network reliability and requirements must be part of the testing.
  • Automation and infrastructure elements are now added as codes, and you have to make sure that they also run properly when microservices are pushed through the pipeline
  • While containerization is universal, you still have to pay attention to specific dependencies and create a testing strategy that allows for those dependencies to be included

Test containers are the method of choice for many developers. Unlike monolith apps, which lets you use stubs and mocks for testing, microservices need to be tested in test containers. Many CI/CD pipelines actually integrate production microservices as part of the testing process.

Contract Testing as an Approach

As mentioned before, there are many ways to test microservices effectively, but the one approach that developers now use reliably is contract testing. Loosely coupled microservices can be tested in an effective and efficient way using contract testing, mainly because this testing approach focuses on contracts; in other words, it focuses on how components or microservices communicate with each other.

Syntax and semantics construct how components communicate with each other. By defining syntax and semantics in a standardized way and testing microservices based on their ability to generate the right message formats and meet behavioral expectations, you can rest assured knowing that the microservices will behave as intended when deployed.

#testing #software testing #test automation #microservice architecture #microservice #test #software test automation #microservice best practices #microservice deployment #microservice components

Harry Patel

Harry Patel

1614145832

A Complete Process to Create an App in 2021

It’s 2021, everything is getting replaced by a technologically emerged ecosystem, and mobile apps are one of the best examples to convey this message.

Though bypassing times, the development structure of mobile app has also been changed, but if you still follow the same process to create a mobile app for your business, then you are losing a ton of opportunities by not giving top-notch mobile experience to your users, which your competitors are doing.

You are about to lose potential existing customers you have, so what’s the ideal solution to build a successful mobile app in 2021?

This article will discuss how to build a mobile app in 2021 to help out many small businesses, startups & entrepreneurs by simplifying the mobile app development process for their business.

The first thing is to EVALUATE your mobile app IDEA means how your mobile app will change your target audience’s life and why your mobile app only can be the solution to their problem.

Now you have proposed a solution to a specific audience group, now start to think about the mobile app functionalities, the features would be in it, and simple to understand user interface with impressive UI designs.

From designing to development, everything is covered at this point; now, focus on a prelaunch marketing plan to create hype for your mobile app’s targeted audience, which will help you score initial downloads.

Boom, you are about to cross a particular download to generate a specific revenue through your mobile app.

#create an app in 2021 #process to create an app in 2021 #a complete process to create an app in 2021 #complete process to create an app in 2021 #process to create an app #complete process to create an app

Tia  Gottlieb

Tia Gottlieb

1597438200

What Is a Microservice Architecture? Why Is It Important Now?

We have been building software applications for many years using various tools, technologies, architectural patterns and best practices. It is evident that many software applications become large complex monolith over a period for various reasons. A monolith software application is like a large ball of spaghetti with criss-cross dependencies among its constituent modules. It becomes more complex to develop, deploy and maintain monoliths, constraining the agility and competitive advantages of development teams. Also, let us not undermine the challenge of clearing any sort of technical debt monoliths accumulate, as changing part of monolith code may have cascading impact of destabilizing a working software in production.

Over the years, architectural patterns such as Service Oriented Architecture (SOA) and Microservices have emerged as alternatives to Monoliths.

SOA was arguably the first architectural pattern aimed at solving the typical monolith issues by breaking down a large complex software application to sub-systems or “services”. All these services communicate over a common enterprise service bus (ESB). However, these sub-systems or services are actually mid-sized monoliths, as they share the same database. Also, more and more service-aware logic gets added to ESB and it becomes the single point of failure.

Microservice as an architectural pattern has gathered steam due to large scale adoption by companies like Amazon, Netflix, SoundCloud, Spotify etc. It breaks downs a large software application to a number of loosely coupled microservices. Each microservice is responsible for doing specific discrete tasks, can have its own database and can communicate with other microservices through Application Programming Interfaces (APIs) to solve a large complex business problem. Each microservice can be developed, deployed and maintained independently as long as it operates without breaching a well-defined set of APIs called contract to communicate with other microservices.

#microservice architecture #microservice #scaling #thought leadership #microservices build #microservice

Desmond  Gerber

Desmond Gerber

1615610278

A New Expiring Item Service For Microservice Environment: Tickler

In this article, learn about Tickler, a new expiring item service for a Microservice environment, and when you may need to use it.

First, let’s define the need for Tickler:

I am, as a Tickler client application, running in distributed microservice environment and I need an expiring distributed data structure in which all of the items in this structure may have different time-to-live values.

These JSON-based expiring items can be called reminders (tickles), which are composed of a callback URL of the client or callback Kafka topic which is consumed by the client, JSON payload for the callback, and a TTL value in seconds.

The main components of a Tickler client and Tickler main application nodes are stated on the image below:

Main components of Tickler client and Tickler main.

#redis #microservice architecture #microservice components #microservice