Source code

Learn about the Actor's source code placement and its structure.

The Apify Actor's source code placement is defined by its Dockerfile. If you have created the Actor from one of Apify's templates then it's by convention placed in the /src directory.

You have the flexibility to choose any programming language, technologies, and dependencies (such as Chrome browser, Selenium, Cypress, or others) for your projects. The only requirement is to define a Dockerfile that builds the image for your Actor, including all dependencies and your source code.

Example setup

Let's take a look at the example JavaScript Actor's source code. The following Dockerfile:

FROM apify/actor-node:20

COPY package*.json ./

RUN npm --quiet set progress=false \
    && npm install --omit=dev --omit=optional \
    && echo "Installed NPM packages:" \
    && (npm list --omit=dev --all || true) \
    && echo "Node.js version:" \
    && node --version \
    && echo "NPM version:" \
    && npm --version \
    && rm -r ~/.npm

COPY . ./

CMD npm start --silent

This Dockerfile does the following tasks:

Builds the Actor from the apify/actor-node:20 base image.
```
FROM apify/actor-node:20
```
Copies the package.json and package-lock.json files to the image.
```
COPY package*.json ./
```

Installs the npm packages specified in package.json, omitting development and optional dependencies.

RUN npm --quiet set progress=false \
    && npm install --omit=dev --omit=optional \
    && echo "Installed NPM packages:" \
    && (npm list --omit=dev --all || true) \
    && echo "Node.js version:" \
    && node --version \
    && echo "NPM version:" \
    && npm --version \
    && rm -r ~/.npm

Copies the rest of the source code to the image
```
COPY . ./
```
Runs the npm start command defined in package.json
```
CMD npm start --silent
```

Optimized build cache

By copying the package.json and package-lock.json files and installing dependencies before the rest of the source code, you can take advantage of Docker's caching mechanism. This approach ensures that dependencies are only reinstalled when the package.json or package-lock.json files change, significantly reducing build times. Since the installation of dependencies is often the most time-consuming part of the build process, this optimization can lead to substantial performance improvements, especially for larger projects with many dependencies.

`package.json`

The package.json file defines the npm start command:

{
    "name": "getting-started-node",
    "version": "0.0.1",
    "type": "module",
    "description": "This is an example of an Apify Actor.",
    "dependencies": {
        "apify": "^3.0.0"
    },
    "devDependencies": {},
    "scripts": {
        "start": "node src/main.js",
        "test": "echo \"Error: oops, the Actor has no tests yet, sad!\" && exit 1"
    },
    "author": "It's not you; it's me",
    "license": "ISC"
}

When the Actor starts, the src/main.js file is executed.