Is there a way to include build id in cache key?

[samueldusek]

Hi,

First of all, thank you for your work. Great stuff!

I have a question regarding the cache key. Is there a way to include the build ID in the cache key as well?

Next.js has a method for setting a stable build ID in next.config.js via the generateBuildId property. It would be helpful if this build ID could be part of the cache key.

Thank you a lot for your answer in advance. 🙂

Samuel

[better-salmon]

Hey @samueldusek, thank you for your interest in my project. There are two ways to achieve your goals. You can use both with custom Handlers, but I will only show createHandler in this example for simplicity.

1. Use env variables

According to the generateBuildId docs, you can use env variables to generate a buildId. It is the recommended way to do it.

In your next.config.js:

module.exports = {
  generateBuildId: async () => {
    // This could be anything, using the latest git hash
    return process.env.GIT_HASH;
  },
};

Then, in your cache-handler.js:

IncrementalCache.onCreation(
  createHandler({
    client,
    keyPrefix: process.env.GIT_HASH,
  })
);

---

If this isn't feasible for you, I have a workaround.

2. The workaround

In your cache-handler.js:

IncrementalCache.onCreation((options) => {
  const { serverDistDir } = options;

  let buildId;

  try {
    buildId = fs.readFileSync(
      path.join(serverDistDir, "..", "BUILD_ID"),
      "utf-8"
    );
  } catch (error) {
    return;
  }

  // You will see this in your logs. If it shows up, you're good to go and can remove the console.log
  console.log("buildId", buildId);

  const handler = createHandler({
    client,
    keyPrefix: `${buildId}:`,
  });

  return handler(options);
});

---

I hope this helps. Let me know if you have any questions. When I restructure this information, I will update the documentation to clarify for others.

[samueldusek]

Great answer! Thank you! 🙂

[better-salmon]

In version 0.6.0, a new context field called buildId was introduced.

You can find more information about it in the documentation.