Thursday, January 26, 2023

Selective Proxying to debug live website issues.

I was recently working on debugging a live website issue; it was only reproducible on the live website, and it was challenging to debug the issue with the live site. Based on my research, I identified selective proxying — modifying the response for the selected URLs and passing the rest of the traffic to the live URL- helping debug live website issues quickly. I want to share some possible tools and configurations that can be used to debug live website issues through selective proxying.

The actual issue was the JavaScript embedded into the HTML page was not working as expected; to debug the problems, the script in the HTML should be modified. Finally, I used the Fiddler Autoresponder to serve only the specific HTML from the Local File and the remaining URLs through live websites. This helps me modify the embed script, identify the root of the problem, and address it.

Fiddler Autoresponder:

The Auto Responder feature in Fiddler Everywhere allows you to create “Rules” triggered when a particular request is issued. Fiddler’s Autoresponder will enable you to return files from your local disk instead of transmitting the request to the server.

The Fiddler can be downloaded from Download Fiddler Web Debugging Tool for Free by Telerik.

Select Autoresponder from Fiddler UI and click Add Rule.

Add the string to match — the URL that should be responded to with local file content.

Select Find File and locate the local File — in my case, I will replace the response for one the HTML — copy the actual HTML response through the view page source in the live URL, store it in the local File, and modify the content as required.

Save and Enable the Rule

Enable the “Decrypt HTTPS Traffic” option if you are debugging HTTPs websites.

Tools → Options → HTTPS

I am selecting No for the root certificate; if the root certificate is not accepted, you will receive an untrusted SSL certificate error while accessing the website — the root certificate can be trusted later if required.

I am enabling the Decrypt only for the browsers.

Click Ok and access the website(page); the specific page will be rendered from a local file — I have enabled a quick alert on the local File.

Now the specific HTML file is loaded locally; all remaining requests are responded to from the live server— including the relative links inside the HTML page loaded from locally.

The SSL certificate error may block some of the externally linked resources from loading; if you want, you can trust the Fiddler root certificate (keep security in mind)

Go to Tools → Option → HTTPS, Click on Actions → Trust Root Certificate.

Follow the screens and Trust the certificate; now, the SSL error will be removed.

You can remove the root certificate if required through Tools →Options → HTTPS →Actions →Reset All Certificates.

The Fiddler is enabled system-wide to capture all the traffic; you can modify the configurations to capture only the specific traffic. Also, you can pause the capturing by unselecting the File →Capture Traffic configuration.


Another option is using the Requestly Desktop app to proxy the response; the Requestly Desktop app can be downloaded from Desktop App to Intercept & Modify HTTP Requests | Requestly

First, open the browser profile (recommend new profile) through the connected app.

Now enable an HTTP Rule.

Select Modify Response Rule

Add the URL for the response that should be replaced — refer to the previous option for replacing HTML with local content.

Place the updated content (in my case, HTML) in the response body.

Provide a Rule name and Save the Rule (Ctrl+S)

Now test the page through the browser session opened by Requestly. For the matching page, the response body is replaced by content specified in the Rule, and the remaining links are directed to the live server.

The Requestly is simple to configure and restricted to a specific browser session, but the Fiddler will give more functionalities like traffic monitoring, SSL support, etc. You can even use other proxies like Charles proxy etc.; consider the security before using any tools for proxying the requests- use the proxies only when you need some debugging.

Tuesday, January 17, 2023

How to support multiple test environments on Coveo Non-Prod Org?

 When you onboard the Coveo search platform by default, you will get two organizations — Prod and Nod Prod, prod can manage the Live search experiences, and non-Prod by default can manage one of the test search experiences, e.g., search on stage platform.

But in most cases, you may need to support multiple test platforms to support various testing, e.g., UAT, Stage, etc.; in this post, let us see one of the approaches to support multiple environments, e.g., UAT, Stage on Coveo Non-Prod organization.

Here the assumption is UAT websites enabled with domains containing uat, e.g.,, and stage websites enabled with the domains containing stage

Login to the Coveo Admin console and select non-Prod organization.

Create two conditions to identify the UAT and Stage environments.

Add two Filter conditions to the query pipelines to filter the content based on the environment conditions defined in the earlier step (filter based on the environment).

Enable UAT/Stage sources — Enable the source (I am using a sitemap source) with both the stage and uat sitemap URLs.

The source index both stage and uat content, but the query pipeline filters the content based on the source_environment and renders it to the end user.

Enable the source_environment context variable to the search page; if you are using the Coveo search page, enable the below event handler — the event handler sets the DNS that accessed the search page to the source_environment context variable. If you are using API to access the search result, pass the source_environment as part of the API context.

Coveo.$$(document.getElementById('coveo-search')).on('buildingQuery', function(e, args) {
args.queryBuilder.addContextValue('source_environment', window.location.hostname);

Now when the user accesses the search result page from the stage environment, the stage content is displayed, and uat data is while accessing the UAT search result page.

Specifying the source_environment context variable while accessing the search result through API.{"country":"us","locale":"es","source_environment":"stage"}&q=xxxx

Refer to Coveo Search Implementation with AEM (Adobe Experience Manager) | by Albin Issac | Tech Learnings | Sep, 2022 | Medium | Tech Learnings for more details on enabling Coveo search for AEM websites.

Monday, January 16, 2023

How are Sling Models resolved to a specific implementation?


Sling Models are annotation-driven Java "POJO's" (Plain Old Java Objects) that facilitate the mapping of data from the JCR to Java variables and provide several other niceties when developing in the context of AEM. When you adapt to a sling model, the model factory returns the specific model implementation; the returned model implementation is selected through the model pickers.

Photo by Clément Hélardot on Unsplash

In this post, let us dive deep into how this model picking works internally.

The Sling Model Framework has the Implementation Picker to select the specific model implementation.

The Implementation Picker interface can be referred to here — ImplementationPicker (Apache Sling 8 API); the picker interface is enabled with a picker method responsible for selecting a specific model implementation.

The Sling Framework, by default, has the below picker implementations.

First Implementation Picker:

This is the default picker implementation; it picks the first implementation from the list alphabetically ordered by class name. If there are multiple implementations of the specific models, this one selects the first one and returns it to the requestor. First Implementation Picker will be used if no other implementations support picking the model implementation.

The service ranking is set to the highest (Integer.MAX_VALUE) to support more custom picker implementations.

Resource Type-Based Resource Picker:

This picks the specific model implementation based on the resource type. This picker's ranking is 0 to ensure this comes before First Implementation Picker.

The AEM core components have their picker implementation to pick the latest version of a model implementation for a specific model.

Latest Version Implementation Picker:

This picks the specific model implementation based on the resource type and the model version —Picks the latest model version of a core component model based on the version information in the package name. The ranking for this picker is specified as 1 to ensure this comes after the Resource Type Based Resource Picker.

All the core components reference the model interface directly — com.adobe.cq.wcm.core.components.models.Carousel; the model implementations are always enabled with a specific version, so the Resource Type Based Resource Picker will not pick any model implementation, and the picking is delegated to the Latest Version Implementation Picker, and this always returns the latest model implementation based on the version number — e.g., com.adobe.cq.wcm.core.components.internal.models.v1.CarouselImpl).

The External models that implement Core Component interfaces have precedence over internal models, allowing us to enable model delegation for the core components.

The custom picker implementation can be enabled by implementing the interface and picker method with your custom model picker logic; the ranking should be enabled accordingly to ensure the default implementations are not impacted.