We think Meteor build tool start to be slow when it has to take care of a lot of files, more than 1,000.
We have created this repo to show that in a simple repository, follow are the steps that we used:
meteor create build-performance-9642 --fullAfter that we installed @babel/runtime because Meteor asked for it
meteor npm install --save @babel/runtimeExperiment: Then we ran Meteor and change the counter quantity on hello.js (to trigger one rebuild) and changed a text on fixtures.js (to trigger another rebuild). You can see that on the files inside private folder.
After that we did the same thing for 1000 fake-files, 2000 and 5000. We used private/fakeFiles.sh to generate those and to import them on /imports/fake/index.js
Between each Experiment we did the commands below to clean up Meteor/NPM stuff:
rm -rf node_modules
meteor reset
meteor npm installSee in the profile logs with a lot of files how Meteor build/rebuild becomes very slow.
Note that we have only simple files with a single empty function but in our real application with have real files that will take longer to be parsed, create the hash, etc