Dependencies caching on local CircleCI builds

Set 26, 2018

At Cloudesire a couple of years ago we decided to switch from Jenkins to CircleCI. First of all, because we are lazy to self-maintain a server and secondly because it offers affordable prices.

A great tool CircleCI provides is the local CLI.
The circleci commands enable you to reproduce the CircleCI environment locally and run jobs as if they were running on the hosted application for more efficient debugging and configuration in the initial setup phase.
The bad news about the local CLI is that the restore_cache key is ignored.
While building you’ll receive the message Error: Skipping cache - error checking storage: not supported in the local builds and dependencies are downloaded each time, shame 🕭 shame 🕭 shame 🕭.

A fast setup solution I currently use is to proxy docker to a local nginx container that acts as cache layer.

Start the proxy container

Start the nginx-cache container

docker run --name nginx-cache -d manuelmazzuola/nginx-cache

and get the internal IP by inspecting it with

docker inspect nginx-cache | grep IPAddress

Proxy docker requests

Create or edit the file ~/.docker/config.json and change it according to the following configuration where {IP} is the internal IP of the cache container:

{
 "proxies":
 {
   "default":
   {
     "httpProxy": "http://{IP}:8080",
     "noProxy": "127.0.0.1,localhost,{IP}"
   }
 }
}

and test it by running the following twice

docker run --rm alpine/httpie --print=hH GET unpkg.com/react@16/umd/react.development.js Cache-Control:no-cache

the first response will contains X-Cached: MISS and the next responses should contain X-Cached: HIT, Eὕρηκα!
But wait, why was the file cached even if Cache-Control:nocache is present? Our nginx-cache container ignores all the caching headers because some build tools, like maven, add the Cache-Control:nocache header to the requests it made ☹

That’s it! Remember that only http requests will be cached, so if you want maven artifacts to be cached you could add an http mirror to your $MAVEN_HOME/conf/settings.xml

<mirror>
  <id>central-secure</id>
  <url>http://repo.maven.apache.org/maven2</url>
  <mirrorOf>central</mirrorOf>
</mirror>

or if you use npm/yarn run the following npm config set registry http://registry.npmjs.org/.

If you want to download your dependencies over HTTP only on your computer you could use a different config file by using circle build -c my-custom-config or inject an env. variable circle build -e LOCAL_BUILD=1 that your build scripts will read and change the repositories according to the value.

Source: Developers’ Corner Blog

Developer's Corner Blog