In today’s fast-paced business environment, managing cloud resources efficiently is crucial to optimizing costs and enhancing security. One effective strategy is to provision resources at the start of the business day and decommission them at the end of the day. This approach helps in reducing hosting costs and minimizing the surface area of any security risks.
Why Automate Resource Management?
Many businesses operate on a standard business day schedule, typically from 9 AM to 5 PM. However, resources such as virtual machines, databases, and storage accounts often remain active 24/7. This continuous operation can lead to unnecessary costs and increased security risks, especially if the resources are not adequately monitored outside business hours.
Automating the provisioning and decommissioning of resources provides several benefits:
Cost Reduction: By only running resources during business hours, you can significantly reduce hosting costs.
Security: Decommissioning resources when not in use reduces the attack surface, thus minimizing potential security risks.
Efficiency: Automation reduces the manual overhead of managing resources, allowing your team to focus on more critical tasks.
In this blog, we will explore how you can use Azure DevOps pipeline schedules to automate this process.
Schedules are added to your pipelines as a cron job where you can specify the time and the days that the pipeline will be triggered. The sample cron job below will trigger the pipeline to run at 7.00am UTC for every work day.
The solution involves two pipelines, one is used for provisioning your resources which is a typical YAML pipeline that you would normally develop to provision your resources. The other pipeline is used for decommissioning your resources. This pipeline uses Azure CLI commands to delete resources by type which you can specify as a variable string. In the example below, this will delete all VM’s, NIC’s and Storage Accounts in the specified Azure resource group.
Source code for a working example can be found here – https://github.com/connectedcircuits/schedule-pipelines. This sample will provision a storage account at 7:00am NZ time and then decommission the resources in the specified Azure Resource Group at 6:00pm NZ time every working day.
You can also add approval gates to the pipelines for added control of provisioning or decommissioning the resources.
Conclusion
By leveraging Azure DevOps pipeline schedules, you can automate the provisioning and decommissioning of resources to align with your business hours. This not only helps in reducing hosting costs but also minimizes the surface area of any security risks. Implement this strategy in your workflow to ensure efficient and secure resource management.
Start automating your resource management today to maximize efficiency and security in your cloud environment!
The motivation of a cyber attacker may fall into one or more of these categories financial gain, political motives, revenge, espionage or terrorism. Once an attacker gets in they may install malware, such as a virus or ransomware. This can disrupt operations, lock users out of their systems, or even cause physical damage to infrastructure. Understanding the motives behind cyber attacks helps to prevent and respond to them effectively.
The primary goal of threat modelling is to identify vulnerabilities and risks before they can be exploited by attackers, allowing organizations to take proactive measures to mitigate these risks.
This should include a list of critical assets and services that need to be protected. Examine the points of data entry or extraction to determine the surface attack area and check if user roles have varying levels of privileges.
Threat modelling should begin in the early stages of the SDLC, when the requirements and the design of the system are being established. This is because the earlier in the SDLC that potential security risks are identified and addressed, the easier and less expensive they are to mitigate. Also, it is advisable to engage your security operations team early in the design phase. Due to the sensitive nature of the threat modelling document, it would be advisable to label the document as confidential and not distribute freely within an organisation.
It is important to revisit the threat model to identify any new security risks that may have emerged and when new functionality is added to a system, or as the system is updated or changed.
Threat modelling is typically viewed from an attacker’s perspective instead of a defender’s viewpoint. Remember the most likely goal or motive of an attacker is information theft, espionage or sabotage. When modelling your threats, ensure you include both externally and internally initiated attacks.
To assist in determining the possible areas of vulnerabilities, a data flow diagram (DFD) would be beneficial. This will give a visual representation of how the application processes the data and highlights any persistent points. It helps to identify the potential entry points an attacker may use and the paths that they could take through the system to reach critical data or functionality.
The How
Let’s go through the process of modelling a simple CRM website which maintains a list of customers stored in a database hosted in Azure.
The hypothetical solution uses a Web Application Gateway to provide HA (High Availability) using two webservices. There are also two microservices, one manages all the SQL Database CRUD operations for customers and the other manages all customers images that are persisted to a blob store. Connection strings to the database are stored in Azure Key vault. Customers use their social enterprise identities to gain access to the website by using Azure AD B2C.
The help with the process of threat modelling the application, a DFD (Data Flow Diagram) is used to show the flow of information between the processors and stores. Once the DFD is completed, add the different trust boundaries on the DFD drawing.
DFD Diagram of the CRM solution
Next, we will start the threat modelling process to expose any potential threats in the solution. For this we use the STRIDE Model developed by Microsoft https://learn.microsoft.com/en-us/azure/security/develop/threat-modeling-tool-threats#stride-model. There are other modelling tools available such as PASTA (Process for Attack Simulation and Threat Analysis), LINDDUN (link ability, identifiability, nonrepudiation, detectability, disclosure of information, unawareness, noncompliance), Common Vulnerability Scoring System (CVSS) and Attack Trees.
The STRIDE framework provides a structured approach to identifying and addressing potential threats during the software development lifecycle
STRIDE is an acronym for Spoofing, Tampering, Repudiation, Information disclosure, Denial of Service, and Elevation of privilege.
The method I use involves creating a table that outlines each of the STRIDE categories, documenting potential threats and the corresponding mitigation measures. Use the DFD to analyse the security implications of data flows within a system and identify potential threats for each of the STRIDE categories. The mitigation may include implementing access controls, encryption mechanisms, secure authentication methods, data validation, and monitoring systems for suspicious activities.
Spoofing (Can a malicious user impersonate a legitimate entity or system to deceive users or gain unauthorized access)
Id
Threat
Risk
Mitigation
SF01
Unauthorized user attempts to impersonate a legitimate customer or administrator account
Moderate
Users authenticate using industrial authentication mechanisms and Administers enforced to use MFA. Azure AD monitoring to detect suspicious login activities.
SF02
Forgery of authentication credentials to gain unauthorized access.
Low
Token based authentication is used to protect against forged credentials
Tampering (Can a malicious user modify data or components used by the system?)
Id
Threat
Risk
Mitigation
TP01
Unauthorized modification of CRM data in transit or at rest.
Moderate
TLS transport is used between all the components. SQL Database and Blob store are encrypted at rest by default.
TP02
Manipulation of form input fields to submit malicious data.
High
Data validation and sanitation is performed at every system process. Configure the Web Application Firewall (WAF) rules to mitigate potential attacks.
TP03
SQL injection attacks targeting the SQL Database.
Moderate
Secure coding practices to prevent SQL injection vulnerabilities. Configure the Web Application Firewall (WAF) rules to mitigate potential attacks.
TP04
Unauthorized changes to the CRM website’s code or configuration.
Low
Source code is maintained in Azure Devops and deployed using pipelines which incorporate code analyses and testing.
Repudiation (Can a malicious user deny that they performed an action to change system state?)
Id
Threat
Risk
Mitigation
RP01
Users deny actions performed on the CRM website.
Low
Logging and audit mechanisms implemented to capture user actions and system events
RP02
Attackers manipulate logs or forge identities to repudiate their actions.
Moderate
Access to log files are protected by RBAC roles.
Information Leakage (Can a malicious user extract information that should be kept secret?)
Id
Threat
Risk
Mitigation
IL01
Customer data exposed due to misconfigured access controls.
High
Follow the principle of least privilege and enforce proper access controls for CRM data.
IL02
Insecure handling of sensitive information during transit or storage.
High
Encryption for sensitive data at rest and TLS is used when in transit.
IL03
Improperly configured Blob Store permissions leading to unauthorized access to customer images.
Moderate
Regularly assess and update Blob Store permissions to ensure proper access restrictions.
Denial of Service (Can a malicious user disrupt or degrade system functionality or availability?)
Id
Threat
Risk
Mitigation
DS01
Application Gateway targeted with a high volume of requests, overwhelming its capacity.
High
Configure appropriate rate limiting and throttling rules on the Application Gateway.
DS02
SQL Database subjected to resource-intensive queries, causing service disruption.
Low
Implemented SQL Database performance tuning and query optimization techniques.
DS03
Azure Blob Store overwhelmed with excessive image upload requests, impacting availability.
Moderate
Exponential back-off is implemented to decrease and to ease out spikes in traffic the store.
Elevation of Privilege (Can a malicious user escalate their privileges to gain unauthorized access to restricted resources or perform unauthorized actions?)
Id
Threat
Risk
Mitigation
EP01
Unauthorized users gaining administrative privileges and accessing sensitive functionalities.
Moderate
Sensitive resource connection strings stored in Key vault. Implement network segmentation and access controls to limit lateral movement within Azure resources. SQL Database hosted inside VNet and access controlled by NSG
EP02
Exploiting vulnerabilities to escalate user privileges and gain unauthorized access to restricted data or features.
Low
Regularly apply security patches and updates to the CRM website and underlying Azure components. Conduct regular security assessments and penetration testing to identify and address vulnerabilities.
Alternative Approach
Instead of going through this process yourself, Microsoft offer a threat modeling tool which allows you to draw your Data Flow Diagram that represents your solution. Then the tool allows you to generate an HTML report of all the potential security issues and suggested mitigations. The tool can be downloaded from here https://learn.microsoft.com/en-us/azure/security/develop/threat-modeling-tool
Conclustion
With the rising sophistication of attacks and the targeting of critical infrastructure, cyber threats have become increasingly imminent and perilous. The vulnerabilities present in the Internet of Things (IoT) further contribute to this escalating threat landscape. Additionally, insider threats, risks associated with cloud and remote work, and the interconnected nature of the global network intensify the dangers posed by cyber threats.
To combat these threats effectively, it is crucial for organisations and individuals to priorities cybersecurity measures, including robust defenses, regular updates, employee training, and strong encryption techniques.
By reading this article, it is hoped that the significance of incorporating threat modeling into your application development process is emphasized.
Would you like to improve compliance and efficiency in your company to get better results from your processes? Business process management (BPM) can help you do just that. According to Gartner, 75% of organizations are in the process of standardizing their operations to stay competitive in today’s market. Connected Circuits outlines the basics you need to know about the BPM methodology and how adopting it can transform your business.
What Is BPM?
BPM is a discipline that uses methods and tools to create a successful business strategy to coordinate the behavior of your employees with the operational systems you have in place. It looks for ways to eliminate rework in your company’s routine business transactions and increase your team’s efficiency.
What Are the Benefits of BPM?
BPM helps you streamline your operations, allowing you to achieve larger company goals. It also helps you take advantage of digital transformation opportunities. Here are the top benefits of adopting this methodology:
Eliminates workflow bottlenecks
Creates more agile workflows
Reduces costs
Increases revenues
Provides security and safety compliance
How Do I Get Started?
There are several steps to follow when implementing BPM at your company.
1. Get Your Staff On Board With the Change
To be successful, your entire staff needs to be on board with the change. Take the time to communicate with your leaders and employees how this process will help create a more productive workflow that results in lower costs, higher revenues and happier customers.
2. Select the Right Methodology and Tools
You will find several options to choose from to reach your goals. Two of the most popular are Lean or Six Sigma. Select the one that meets your needs and falls within your current budget. You can always upgrade to a more extensive program in the future.
Before investing in any technical tools or software, make sure help is available when you have technical problems with the program or tool. A great way to test this before you make a purchase is to call their support desk during your business hours to determine if assistance is available as promised.
3. Design a New Process
First, take a look at the current processes in place to make sure they align with your goals and are in compliance with any regulations. Then, look for any overlap of tasks that are no longer necessary. Finally, Integrify suggests designing a new process model to streamline operations and increase efficiency. Include Key Process Indicators (KPIs) to measure your results.
4. Implement the New Process
It’s a good idea to first test the new process with a small group of users to work out any unexpected issues before releasing it on a larger scale.
5. Analyze the Results
After implementing the new process, it’s time to analyze the results. Use your KPIs to track your metrics in each process to determine if this model is successful. The data may show the need to make additional adjustments to the workflow.
6. Optimize Your Company’s Processes
Use the data collected in your results to create an overall strategy to streamline and strengthen your business processes.
Adopting the BPM methodology at your company can transform your business by making your operations more efficient. These changes ultimately lead to an improved experience for your customers and higher profits for your company.
There are times when you simply need to replace tokens with actual values in text files during the deployment phase of a solution. These text files may be parameter or app setting files or even infrastructure as code files such as ARM/Bicep templates.
Here I will be building a reusable template to insert the pipeline build number as a Tag on some LogicApps every time the resources are deployed from the release pipeline. Using the process describe below can easily be used to replace user defined tokens in other types of text files by supplying the path to the file to search in, the token signature and the replacement value.
I used the PS script below to read in the text file contents and then search and replace the token with the required value. The PS script uses several parameters so it may be reused throughout the release pipeline for many different text file types and tokens.
The PS script is called from a template file below which takes a list of files to search as one of the template parameters. This allows me to search for the token across multiple files in one hit. The template iterates through each file calling the PS script and passing the file path and the other required parameters.
The yml release pipeline file is shown below which calls the template at line 19 to replace the tokens in the LogicApp.parameters.json files. In this scenario, the token name to search for is specified at line 24. You need to ensure the chosen token name does not clash with any other valid text.
The last step at line 27 deploys the LogicApps to the specified resource group.
Executing the pipeline will read the following LogicApp parameter file from the source code folder on the build agent and then replace the buildNumber token with the actual value.
When developing a solution that has multiple projects and parameter files, more than likely these parameter files will have some common values shared between them. Examples of common values are the environment name, connection strings, configuration settings etc.
A good example of this scenario are Logic App solutions that may have multiple projects. These are typically structured as shown below where each project may several parameter files, one for each environment. Each of these parameter files will have different configuration settings for each of the 3 environments but are common across all the projects.
Keeping track of the multiple parameter files can be a maintenance issue and prone to misconfiguration errors. An alternative is to use a global parameter file which contains all the common values used across the projects. This global file will overwrite the matching parameter value in each of the referenced projects when the projects are built inside a CI/CD pipeline.
By using global parameter files, the solution will now look similar to that shown below. Here all the common values for each environment are placed in a single global parameter file. This now simplifies the solution as there is now only one parameter file under each project and all the shared parameter values are now in a global parameter file. The default global values for the parameter files under each Logic App project will typically be set to the development environment values.
The merging of the global parameter files is managed by the PowerShell script below.
# First parameter is the source param and the second is the destination param file.
param ($globalParamFilePath,$baseParamFilePath)
# Read configuration files
$globalParams = Get-Content -Raw -Path $globalParamFilePath | ConvertFrom-Json
$baseParams = Get-Content -Raw -Path $baseParamFilePath | ConvertFrom-Json
foreach ($i in $globalParams.parameters.PSObject.Properties)
{
$baseParams.parameters | Add-Member -Name $i.Name -Value $i.Value -MemberType NoteProperty -force
}
# Output to console and overwrite base parameter file
$baseParams | ConvertTo-Json -depth 100 |Tee-Object $baseParamFilePath
The script is implemented in the release pipeline to merge the parameter files during the build stage. A full working CI/CD pipeline sample project can be downloaded from my GitHub repo here https://github.com/connectedcircuits/globalParams
In the solution mentioned above, I have 2 Logic App projects where the parameter files have the following content.
Running the release pipeline produces the following merged file which is used by the pipeline to deploy the Logic Apps to Azure.
The Logic App resource file uses these parameters to create some tags and appends the environment variable to the Logic App name as shown below.
Using Environment variables available in Azure DevOPs is another option, but I like to keep the parameter values in code rather than have them scattered across the repo and environment variables.
Content based routing is where the message routing endpoint is determined by the contents of the message at runtime. Instead of using an Azure Logic App workflow to determine where route the message, I decided to use Azure APIM and a custom policy. The main objective of using an APIM policy was to allow me to add or update the routing information through configuration rather than code and to add a proxy API for each of the providers API endpoints.
Below is the high level design of the solution based on Azure APIM and custom policies. Here the backend ERP system sends a generic PO message to the PO Routing API which will then forward the message onto the suppliers proxy API based on the SupplierId contained in the message. The proxy API will then transform the generic PO to the correct format before being sent to the supplier’s API.
The main component of this solution is the internal routing API that accepts the PO message and uses a custom APIM Policy to read the SupplierId attribute in the message. The outbound URL of this API is then set to the internal supplier proxy API by using a lookup list to find the matching reroute URL for the SupplierId. This lookup list is a JSON array stored as a Name-Value pair in APIM. This allows us to add or update the routing information through configuration rather than code.
Here is the structure of the URL lookup list which is an array of JSON objects stored as a Name-value pair in APIM.
The code below is the custom policy for the PO Routing API. This loads the above JSON URL Lookup list into a variable called “POList”. The PO request body is then loaded into a JObject type and the SupplierId attribute value found. Here you can use more complex queries if the required routing values are scattered within the message.
Next the URL Lookup list is converted into a JArray type and then searched for the matching SupplierId which was found in the request message. The variable “ContentBasedUrl” is then set to the URL attribute of the redirection object. If no errors are found then the backend url is set to the internal supplier’s proxy API and the PO message forwarded on.
// Get the URL Lookup list from the Name-value pair in APIM
<set-variable name="POList" value="{{dev-posuppliers-lookup}}" />
<set-variable name="ContentBasedUrl" value="@{
JObject body = context.Request.Body.As<JObject>(true);
// Create an JSON object collection
try
{
// Get the AccountId from the inbound PO message
var supplierId = body["Purchase"]?["SupplierId"];
var jsonList = JArray.Parse((string)context.Variables.GetValueOrDefault<string>("POList"));
// Find the AccountId in the json array
var arr = jsonList.Where(m => m["SupplierId"].Value<string>() == (string)supplierId);
if(arr.Count() == 0 )
{
return "ERROR - No matching account found for :- " + supplierId;
}
var url = ((JObject)arr.First())["Url"];
if( url == null )
{
return "ERROR - Cannot find key 'Url'";
}
return url.ToString();
}
catch( Exception ex)
{
return "ERROR - Invalid message received.";
}
}" />
<choose>
<when condition="@(((string)context.Variables["ContentBasedUrl"]).StartsWith("ERROR"))">
<return-response>
<set-status code="400" />
<set-header name="X-Error-Description" exists-action="override">
<value>@((string)context.Variables["ContentBasedUrl"])</value>
</set-header>
</return-response>
</when>
</choose>
<set-backend-service base-url="@((string)context.Variables["ContentBasedUrl"])" />
</inbound>
<backend>
<base />
</backend>
<outbound>
<base />
</outbound>
<on-error>
<base />
</on-error>
Supplier Proxy API
A proxy API is created for each of the suppliers in APIM where the backend is set to the suppliers API endpoint. The proxy will typically have the following policies.
The map in the Outbound section of the policy takes the response message from the Suppliers API and maps it to the generic PO response message which is then passed back to the PO Routing API and then finally to the ERP system as the response message.
Also by adding a proxy for each of the supplier’s API provides decoupling from the main PO Routing API, allowing us to test the suppliers API directly using the proxy.
The last step is to add all these API’s to a new Product in APIM so the subscription key can be shared and passed down from the Routing API to the supplier’s proxy APIs.
For the last few months I have busy developing the above course for EC-Council. This is my first endeavour doing something like this and wanted to experience the process of creating an online course.
The course will take you through the steps of designing and developing an enterprise-ready API from the ground up, covering both the functional and non-functional design aspects of an API. There is a total of 7 chapters equating to just over 4 hours of video content covering the following topics:
Learn the basics of designing an enterprise level API.
Learn about the importance of an API schema definition.
Learn about the common non-functional requirements when designing an API.
Develop a synchronous and asynchronous API’s using Azure API App and Logic Apps
Understand how to secure your API using Azure Active Directory and custom roles.
Set up Azure API Management and customizing the Developer Portal.
Article written and submitted by Gloria Martinez, email info@womanled.org
Developing an app for your business is a great way to tune into the wants and needs of your customer base, but it’s important to take your time and do it right. Many apps begin as strong ideas but lose something in the execution, making things like beta testing and User Acceptance Testing essential parts of the process. While this can help you work out kinks in the design, it’s also the best way to ensure that your app meets your goals. Presented by Connected Circuits, here are a few tips on how you can avoid common development mistakes when you’re ready to create your own app.
Recruit the best talent
As with any important project, it’s crucial to start by finding the best talent for the job. The right app designer will keep both your needs and a user-friendly element in mind as they create your app, ensuring that the end result is consistent when used across multiple products and devices. These days, finding mobile app designers is easier than ever with job boards that give you access to experienced designers. You can read reviews of their work, see pricing, and compare timeframes for a finished product.
When you hire someone to handle the job, make sure you understand how to properly pay for their services. If you haven’t done so already, you need to set up your payroll system. There are many time tracking apps that allow your employees to access schedules and team management information. What’s more, these apps allow you to access this info from mobile devices.
Have a clear vision
When you don’t have a clear vision for a project, the end result will likely be difficult for your customers to understand and use. Define your goals from the very beginning — not only is this essential for your own success, but also for the success of your designer. Do market research to find out what other businesses are doing with their apps, and think about what you could bring to the table that’s different. Who is your target customer? Be realistic when it comes to your reasons for developing an app, asking yourself whether there truly is a need for it or if you’re simply trying to keep up with the times.
Offer plenty of reasons to come back
Not only does your app need to be necessary, but it also needs to offer your customers the features they want while providing meaningful analytics and other benefits for you. Many users these days are fickle when it comes to tech and don’t have much patience for apps that lag, have nothing special to offer, or are full of bugs, so you may only have a minute or so of user experience before they give up and try something else. Blow them away with easy-to-use design and features that will make their lives easier, such as swift, secure payment options and reminders for sales, events, and billing. When they can see the benefits right away, they’ll be more likely to return and keep using the service.
Keep it simple
While the app should have everything your customer wants and needs, it shouldn’t be complicated. Your business app should stay simple in design and execution, making it easy for even inexperienced users to interact with. Think about the most important elements of the app and make those the star attraction, stripping down extras to streamline. In beta testing, users should be able to quickly figure out how to navigate the app to find what they’re looking for. Keep in mind that you’ll want to have a backup plan in place before your product goes into beta testing so that small changes can easily be made. Remember, as well, that the beta testing process requires some planning in order to receive the most accurate feedback.
Developing an app for your business takes time and lots of thoughtful planning, and it also requires quite a bit of research. Make sure your goals have a realistic timeline, as this will prevent unnecessary stress on both you and your designer. With the right moves, you can create a successful app that benefits both you and your customers.
An API definition may be thought of as an electronic equivalent of a receptionist for an organisation. A receptionist is normally the first person they see when visiting an organisation and their duties may include answering enquires about products and services.
This is similar to an API definition, when someone wants to do business electronically, they would use the API definition to obtain information about the available services and operations.
My thoughts are, API’s should be built customer first and developer second. Meaning an API needs to be treated as a product and to make it appealing to a consumer, it needs to be designed as intuitive and usable with very little effort.
Having standardised API definition documents across all your API’s, allows a consumer to easily navigate around your API’s as they will all have a consistent look and feel about them. This specially holds true when there are multiple teams developing Microservices for your organisation. You don’t want your consumers think they are dealing with several different organisations because they all look and behave differently. Also, when generating the client object models from several different API definitions from the same organisation, you want the property names to all follow the same naming conventions.
To ensure uniformity across all API schema definitions, a linter tool should be implemented. One such open-source tool is Spectral https://github.com/stoplightio/spectral from Stoplight, however there are many other similar products available.
Ideally the validation should be added as a task to your CI/CD pipelines when committing the changes to your API definition repository.
Using Spectral in MS DevOps API Projects
Spectral provides the capability to develop custom rules as a yaml or json file. I typically create a separate DevOps project to store these rules inside a repository which may be shared across other API projects.
Below is how I have setup the repositories section in the pipeline to include the linter rules and the API definition.
After downloading the Spectral npm package in the pipeline, I then run the CLI command to start the linter on the schema specification document which is normally stored in a folder called ‘specification’ in the corresponding API repository.
An example of the pipeline job can be seen below. Here the job failed due to some rule violations.
This blog is about using the Event Driven architecture pattern to synchronise data across multiple services. I typically use this when several Microservices have their own database (Database per service) and are required to either cache or locally persist slow changing data as read-only retrieved from another source.
I mentioned slow changing data because using this pattern provides eventual data consistency. If data changes too rapidly, the subscribers may never keep up with the changes.
This other source would typically be an authoritative Microservice that sends out an event to any interested parties whenever its data has been modified. The events are typically lightweight and there is no strong contract between publisher and subscribers. Normally these events do not contain the updated data, it’s simply a notification to say something has been updated. If you want the actual changes, then come a get it by using another mechanism. This could be a HTTP Request/Response on another endpoint belonging to the authoritative service.
Microservices that cache or persisting external data locally have the following benefits:
Removes the dependency from any authoritative Microservices.
Avoids API Composition by not having to query across multiple services.
Improved overall performance of the Microservice.
Promotes loose coupling between Microservices.
Reduces network traffic and chatter between Microservices.
Below is the high level solution using Azure Event Grid to publish events and Logic Apps as subscribers.
Whenever specific data is updated in the authoritative Microservice, the service will also publish an event to Azure Event Grid as it provides a lightweight HTTP call-back function to the registered subscribers.
A Logic App is used as the event handler with a HTTP Trigger and will be the call-back endpoint for the Event Grid subscriber. Using a Logic App abstracts the data synchronisation process away from the actual downstream Microservice logic. Also the Logic App provides a number of available connectors for different data stores out of the box if pushing the data directly to the database is desired. Or the other alternative is the Logic App calls an API endpoint on the downstream Microservice to update the repository.
Use-case
A typical scenario would be an E-Commerce website which manages online orders from customers. This type of application would normally comprise of multiple Microservices. This may involve a CRM service which will be the authoritative service for the customer information, a Delivery service that manages the dispatch of orders.
To improve the performance of the Delivery service, a copy of the customers address would be persisted in the local database rather than query CRM each time an order is to be dispatched. This removes the dependency on the CRM service being available when dispatching orders..
This E-Commerce solution may also incorporate an Accountancy service which publishes an event whenever the customer’s account status changes from active to on-hold or vice versa. The Cart and Delivery Microservices would subscribe to this this event and persist the status of the customer locally. Again it’s the same architecture pattern as before except the event data may contain the customer’s account status as this data would be relatively small.
Below is the complete sequence diagram of the events between the artefacts.
Whenever the website calls the CRM service to update the customers information, the service will also publish a custom event to the Azure Event Grid Topic.
The structure of the data payload has several properties, the customer Id, the event source and the CRM endpoint URL to retrieve the updated data. The value in the CallbackUrl property is what the Logic App will use to retrieve the full address dataset from the CRM service.
For the event handler, a Logic App with a Http request trigger is used. This provides the necessary workflow logic and built-in connectors to query the CRM service via HTTP and then update the Delivery Microservice database using the SQL Db connector.
Simple POC
To simulate the CRM service publishing events, I created a simple console app to publish several events onto the Event Grid. The code for the console app can be found here: https://github.com/connectedcircuits/azureeventgridpub
The Logic App workflow is shown below. The ‘For each Event’ iterates through each event calling the CRM endpoint defined in the event data. The switch task evaluates the event subject to determine the crud operation and the Db stored procedure to call to update the local database.
Below is a sample received HTTP request sent by Azure Event Grid and the event subscription filter is based on the eventType and subject values.
Final thoughts
Enabling the dead lettering feature of the Azure Event Grid is recommended to track which consumers are not responding to the events and remember to setup alerting and monitoring around this.
If a subscriber misses a notification event, what kind of compensation transaction should occur. If events are received out of order, what should happen. These types of questions are typically answered by the business analyst.
Some form of event tracking mechanism should also be incorporated into the solution. Imagine there may be several hundred events per minute and trying to trace an event to a subscriber would be quite difficult. This could involve using a session Id that can be tracked across all services involved in the event.
When there are multiple subscribers interested in the same event and they all call the same endpoint to retrieve the full dataset, the authoritative Microservice should use some form of caching mechanism on the response object to improve performance.
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