.npm cache vs node_modules size

Question

When building our node application, we are using .npm cache as follows:

npm install --cache /tmp/node-cache/.npm --prefer-offline

However I have reasons to believe, the cache is not working properly as:

/tmp/node-cache/ # du -sh .npm/
177M    .npm/

/tmp/build/ # du -sh node_modules/
1.1G    node_modules

Does this mean the build downloaded additional 900 M and not caching them in .npm directory?

Answer 1

Does this mean the build downloaded additional 900 M and not caching them in .npm directory?

That's possible. But it's also possible that the difference is due to a combination of compression and build artifacts.

The npm cache is compressed. node_modules directories are uncompressed.

Furthermore, npm almost certainly only caches the source code. If you are using something like node-sass, PhantomJS, puppeteer, or some other thing that has a custom install script or other build step, then build artifacts may balloon your node_modules.

I would not necessarily conclude merely from the size difference that the cache is not being respected. You'll have to do more investigation. One thing you might try is:

• Remove node_modules (and package-lock.json if it exists)
• npm cache clean --force and confirm that the cache is very small
• npm install
• Check the sizes of node_modules and the cache again.