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The metamorph operation transforms an Actor run into the run of another Actor with a new input.

This feature is useful if you want to use another Actor to finish the work of your current one instead of internally starting a new Actor run and waiting for it to finish. With metamorph, you can easily create new Actors on top of existing ones, and give your users a nicer input structure and user interface for the final Actor. The metamorph operation is completely transparent to the Actor's users; they will just see that your Actor got the work done.

Internally, the system stops the Docker container corresponding to the Actor run and starts a new container using a different Docker image. All the default storages are preserved, and the new input is stored under the INPUT-METAMORPH-1 key in the same default key-value store.

There is a limit on how many times you can metamorph a single run. You can check the limit in the Actor runtime limits.

To make your Actor compatible with the metamorph operation, use Actor.getInput() instead of Actor.getValue('INPUT'). This method will fetch the input using the right key INPUT-METAMORPH-1 in case of a metamorphed run.

For example, imagine you have an Actor that accepts a hotel URL on input and then internally uses the apify/web-scraper Actor to scrape all the hotel reviews. The metamorphing code would look like this:

import { Actor } from 'apify';

await Actor.init();

// Get input of your Actor.
const { hotelUrl } = await Actor.getInput();

// Create input for apify/web-scraper
const newInput = {
startUrls: [{ url: hotelUrl }],
pageFunction: () => {
// Here you pass the page function that
// scrapes all the reviews ...
// ... and here would be all the additional
// input parameters.

// Transform the Actor run to apify/web-scraper
// with the new input.
await Actor.metamorph('apify/web-scraper', newInput);

// The line here will never be reached, because the
// Actor run will be interrupted.
await Actor.exit();