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Step 10: Computation Caching

Video of this Lesson

Nx has built-in computation caching, which helps drastically improve the performance of the commands.

To see it in action, run npx nx build todos:

> npx nx run todos:build
Generating ES5 bundles for differential loading...
ES5 bundle generation complete.

chunk {runtime} runtime-es2015.js, runtime-es2015.js.map (runtime) 6.16 kB [entry] [rendered]
chunk {runtime} runtime-es5.js, runtime-es5.js.map (runtime) 6.16 kB [entry] [rendered]
chunk {polyfills} polyfills-es2015.js, polyfills-es2015.js.map (polyfills) 141 kB [initial] [rendered]
chunk {main} main-es2015.js, main-es2015.js.map (main) 22.7 kB [initial] [rendered]
chunk {main} main-es5.js, main-es5.js.map (main) 24.1 kB [initial] [rendered]
chunk {styles} styles-es2015.js, styles-es2015.js.map (styles) 9.88 kB [initial] [rendered]
chunk {styles} styles-es5.js, styles-es5.js.map (styles) 11.1 kB [initial] [rendered]
chunk {polyfills-es5} polyfills-es5.js, polyfills-es5.js.map (polyfills-es5) 759 kB [initial] [rendered]
chunk {vendor} vendor-es2015.js, vendor-es2015.js.map (vendor) 2.35 MB [initial] [rendered]
chunk {vendor} vendor-es5.js, vendor-es5.js.map (vendor) 2.75 MB [initial] [rendered]

Now, run npx nx build todos again, and you will see the results appearing instantly:

> npx nx run todos:build

>  NX   NOTE  Cached Output:

Generating ES5 bundles for differential loading...
ES5 bundle generation complete.

chunk {polyfills-es5} polyfills-es5.js, polyfills-es5.js.map (polyfills-es5) 759 kB [initial] [rendered]
chunk {polyfills} polyfills-es2015.js, polyfills-es2015.js.map (polyfills) 141 kB [initial] [rendered]
chunk {main} main-es2015.js, main-es2015.js.map (main) 22.5 kB [initial] [rendered]
chunk {main} main-es5.js, main-es5.js.map (main) 23.9 kB [initial] [rendered]
chunk {vendor} vendor-es2015.js, vendor-es2015.js.map (vendor) 2.35 MB [initial] [rendered]
chunk {vendor} vendor-es5.js, vendor-es5.js.map (vendor) 2.75 MB [initial] [rendered]
chunk {styles} styles-es2015.js, styles-es2015.js.map (styles) 9.88 kB [initial] [rendered]
chunk {styles} styles-es5.js, styles-es5.js.map (styles) 11.1 kB [initial] [rendered]
chunk {runtime} runtime-es2015.js, runtime-es2015.js.map (runtime) 6.16 kB [entry] [rendered]
chunk {runtime} runtime-es5.js, runtime-es5.js.map (runtime) 6.16 kB [entry] [rendered]

Based on the state of the source code and the environment, Nx was able to figure out that it had already run this exact command. Nx found the artifact in the local cache and replayed the output and restored the necessary files.

Caching only works with the Nx CLI. Running ng build todos will run the command every single time.

Building Multiple Projects

Now, run npx nx run-many --target=build --projects=todos,api to rebuild the two applications:

Nx read the output from cache instead of running the command for 1 out of 2 projects.

Nx built api and retrieved todos from its computation cache. Read more about the cache here here.

--with-deps

As we saw already, Nx is smart, so it knows how applications and libraries in the workspace depend on each other.

Run npx nx lint todos --with-deps, and you see that Nx lints both the todos app and the libraries it depends on.

>  NX  Running target lint for project todos and its 2 deps.

———————————————————————————————————————————————

> npx nx run todos:lint

Linting "todos"...

All files pass linting.


> npx nx run ui:lint

Linting "ui"...

All files pass linting.


> npx nx run data:lint

Linting "data"...

All files pass linting.


———————————————————————————————————————————————

>  NX   SUCCESS  Running target "lint" succeeded

Add --parallel to any command, and Nx will do most of the work in parallel.

Quiz

Run npx nx lint api --with-deps. What do you see?

  • Nx read the output from cache instead of running the command for 1 out of 2 projects.

  • Cannot lint data error

  • Everything was retrieved from the cache