Sitecore JSS – NEXT.js – Exploring the Incremental Site Regeneration (ISR).

Next.js allows you to create or update static pages after you’ve built your site. Incremental Static Regeneration (ISR) enables developers and content editors to use static-generation on a per-page basis, without needing to rebuild the entire site. With ISR, you can retain the benefits of static while scaling to millions of pages.

Static pages can be generated at runtime (on-demand) instead of at build-time with ISR. Using analytics, A/B testing, or other metrics, you are equipped with the flexibility to make your own tradeoff on build times.

Consider an e-commerce store with 100,000 products. At a realistic 50ms to statically generate each product page, the build would take almost 2 hours without ISR. With ISR, we can choose from:

Faster Builds → Generate the most popular 1,000 products at build-time. Requests made to other products will be a cache miss and statically generate on-demand: 1-minute builds.

Higher Cache Hit Rate → Generate 10,000 products at build-time, ensuring more products are cached ahead of a user’s request: 8-minute builds.

Exploring ISR

In my previous post I’ve created a JSS-Next.js app that we deployed to Vercel. I also created a Web Hook to trigger a full rebuild in Vercel (SSG). Now, I’ll explain how the ISR works in this same app.

Fetching Data and Generating Paths

Data:

ISR uses the same Next.js API to generate static pages: getStaticProps.
By specifying revalidate: 5, we inform Next.js to use ISR to update this page after it’s generated.

Check the src/pages/[[…path]].tsx file and the getStaticProps function:

Paths:

Next.js defines which pages to generate at build-time based on the paths returned by
getStaticPaths. For example, you can generate the most popular 1,000 products at build-time by returning the paths for the top 1,000 product IDs in getStaticPaths.

With this configuration, I’m telling Next.js to enable ISR and to revalidate every 5 sec. After this time period, the first user making the request will receive the old static version of the page and trigger the revalidation behind the scenes.

The Flow

  1. Next.js can define a revalidation time per-page (e.g. 5 seconds).
  2. The initial request to the page will show the cached page.
  3. The data for the page is updated in the CMS.
  4. Any requests to the page after the initial request and before the 5 seconds window will show the cached (hit) page.
  5. After the 5 second window, the next request will still show the cached (stale) page. Next.js triggers a regeneration of the page in the background.
  6. Once the page has been successfully generated, Next.js will invalidate the cache and show the updated product page. If the background regeneration fails, the old page remains unaltered.

Page Routing

Here’s a high-level overview of the routing process:

In the diagram above, you can see how the Next.js route is applied to Sitecore JSS.

The [[…path]].tsx Next.js route will catch any path and pass this information along to getStaticProps or getServerSideProps on the context object. The Page Props Factory uses the path information to construct a normalized Sitecore item path. It then makes a request to the Sitecore Layout Service REST API or Sitecore GraphQL Edge schema to fetch layout data for the item.

Demo!

So, back to our previously deploied app in Vercel, login to Sitecore Content Editor and make a change on a field. I’m updating the heading field (/sitecore/content/sitecoreverceldemo/home/Page Components/home-jss-main-ContentBlock-1) by adding “ISR Rocks!”. We save the item and refresh the page deployed on Vercel. (Don’t publish! this will trigger the webhook that is defined in the publish:end event).

After refreshing the page, I can still see the old version:

But, if I keep checking what is going on in the ngrok, I can see the requests made to the layout service:

So, after refreshing again the page, I can see the changes there!

So, it got updated without the need of rebuilding and regeneating the whole site.

That’s it! I hope this post helps to understand how the ISR works and how to start with it on your Sitecore JSS implementation.

Thanks for reading and stay tuned for more Sitecore stuff!

Deploying a Sitecore JSS-Next.js App with SSG & ISR to Vercel (from zero to live)

In this post I’ll share the steps to get our Next.js Sitecore App deployed into Vercel on some simple steps. Vercel is the creator of Next.js and now also a Sitecore partner. To avoid a huge and extensive post, I won’t be writting about Next.js, Vercel, JSS, etc. instead, please find some useful links with references to all those at the end of the blog post.

Getting the JSS app locally

The first step is to have the Sitecore JSS-Next.js app running locally. For simplifying things, we’ll be creating it with the help of JSS CLI. Before start, make sure you’ve Node.js installed locally.

We just get started by running the following command to install the JSS CLI (more info here):

npm install -g @sitecore-jss/sitecore-jss-cli

Now, we can start to play with the CLI, so let’s create the app:

jss create sitecoreverceldemo nextjs

We give it a name (sitecoreverceldemo) and a framework (nextjs).

Connected Mode

The first thing we need to do is to create our API key so our JSS app can communicate to our Sitecore instance. In this demo I’m running a local Sitecore instance, but it could be also a containerized one.

So, for doing that, we login into Sitecore and go to /sitecore/system/Settings/Services/API Keys and we create a new item, we give it a name and copy the ID somewhere, this gonna be our API key moving forward.

Now, we run the following command to start setting up it:

jss setup

We just follow the wizard and set the proper values for our Sitecore instance, API Key, import service URL, etc. If all went well, then you should see something like this:

Note that you’ve to add the recently created hostname to the hosts file in windows and ISS (sitecore.vercel.demo).

We’re now ready to deploy the configs, and right after that, the items, for doing that we simply run the following commands:

jss deploy config
jss deploy items --includeContent --includeDictionary

This will run the import to Sitecore and create the sample items. We can now build the app by running:

jss build

That’s it! We can now start our JSS App in connected mode:

jss start:connected

Code Repository

We now run some Git commands to push our code to GitHub. You can find the one I’m using for this demo here.

Vercel

Now, that we are done with our JSS Next.js app, we can have fun deploying it to Vercel. First good news here, you can go and create your free account for testing purposes 🙂

Another good thing about Vercel is that it connects to GitHub, GitLab and Bitbucket, so it makes things really easy. So, let’s go and import our GitHub repo there:

Let’s click on import and then configure our project. (Note: skip the Teams creation step to avoid having to get a trial account).

BUT as we have our Sitecore instance locally (or running on a container) we’ve to somehow expose our localhost to the internet. For that we can use this amazing tool: Ngrok.

As I’m using the free version, it generates random URLs, but this is enough for our demo. Don’t forget to add those to the IIS binding and hostfile (if you’re running Sitecore locally).

Back to Vercel, we have to setup some environment variables:

SITECORE_API_KEY: The Sitecore API key we created in the previous step.
SITECORE_API_HOST: The URL generated by NGRock.
JSS_EDITING_SECRET: Your secret token. The JSS_EDITING_SECRET is optional for deployments but necessary if you want to use the Experience Editor with your Next.js Vercel deployment.

In next.config.js, replace:

const publicUrl = process.env.PUBLIC_URL;

with the following:

const publicUrl = process.env.VERCEL_URL ? https://${process.env.VERCEL_URL} : process.env.PUBLIC_URL;

So, it takes the URL we defined as environment variable in Vercel.

Now everything is set and ready to be deployed. Let’s get back to Vercel, and deploy!

You’ll need to also update the hostname in sitecore/config/sitecoreverceldemo.config.

If everything was well configured, you should be able to see the requests to the headless services while Next.js is generating the static siteduring the building, something like this:

Et voila! The site is now live!

The publishing webhook

We need now to trigger the deploy if a content gets changed in the CMS. For that, we create a deploy hook in Vercel:

In the settings/Git section, we choose to create a deploy hook, we give it a name and a branch (develop in this case).

Create the hook and copy the URL. Let’s create now a config patch in Sitecore that will trigger it on publush:end

<configuration xmlns:patch="http://www.sitecore.net/xmlconfig/" xmlns:role="http://www.sitecore.net/xmlconfig/role/" xmlns:search="http://www.sitecore.net/xmlconfig/search/">
  <sitecore>
    <javaScriptServices>
      <publishWebHooks type="Sitecore.JavaScriptServices.AppServices.WebHooks.WebHooks, Sitecore.JavaScriptServices.AppServices">
        <hooks hint="list:AddWebHook">
          <hook type="Sitecore.JavaScriptServices.AppServices.WebHooks.WebHookDefinition, Sitecore.JavaScriptServices.AppServices">
            <name>Vercel - Publish Hook</name>
            <url>https://api.vercel.com/v1/integrations/deploy/prj_f4NcDuveH3zCP9a6pObWlaApER14/T7ATu61aej</url>
            <method>POST</method>
            <site>sitecoreverceldemo</site>
            <body></body>
          </hook>
        </hooks>
      </publishWebHooks>
    </javaScriptServices>
  </sitecore>
</configuration>
  • url: Required. The URL of the hook to be invoked.
  • method: Optional. The HTTP method for invoking webhook. Possible values are POST or GET. The default method is POST.
  • site: Optional. The sites which should trigger the webhook when published. By default, Sitecore will trigger the webhook for every published item. If you provide the site parameter, the webhook will be invoked if the published item root is an ancestor, descendant, or equal to the configured site’s root item.

Let’s test it, make a quick change in Sitecore and publish the item (heading field):

After publishing, we can see that the deploy hook got triggered in Vercel:

Refresh the site, and we can see our changes there:

In my next post I’ll explain a bit how the ISR works as it deserves a specific writting about it.

That’s it! As you can see the steps to setup your CI/CD with Vercel is quite straightforward. I hope you find this post useful and helps you with the first steps getting into Next.js and Vercel. Stay tuned for more Sitecore stuff!

References: