Differy - MDN's partial update bundler

Due to the nature of yari we don't know which articles changed since out last build. The kuma script in an unmodified file might render different that it did last time. At some point we should solve this in yari, but now for now.

Why

We need content bundles for the offline capability of the MDN apps. Further, we need daily updates to deliver new content without downloading the huge content bundle. Differy creates these bundles and a GitHub action uploads them for distribution.

Basic Usage and Example

Differy generates updates based on a list of hashes of all files generated in previous builds. As input we additionally need a fresh build of mdn/content and mdn/interactive-examples and the short-rev of the mdn/content

differy package $BUILD_OUT_ROOT --rev  $(cd $CONTENT; git rev-parse --short HEAD)

On top of that we want a reference "update.json" and the checksum archives for all version we want to generate updates for.

Output

The $BUILD_OUT_ROOT directory should contain the artifacts of:

• yarn build:prepare && yarn build -n from mdn/content
• yarn build from mdn/interactive-examples

Differy generates:

• xxxxxxxxx-content.zip: All of $BUILD_OUT_ROOT
• xxxxxxxxx-app-content.zip: All of $BUILD_OUT_ROOT
• xxxxxxxxx-content.json: a json file containing the names of all content files. with modified links to interactive-examples
• xxxxxxxxx-yyyyyyyyy-update.zip: the changed files between xxxxxxxxx and yyyyyyyyy plus a file called removed containing list of all files that have been removed
• xxxxxxxxx-yyyyyyyyy-app-update.zip: the same with modified links
• xxxxxxxxx-yyyyyyyyy-diff.json: a json file containing the names of changed files between xxxxxxxxx and yyyyyyyyy have been removed
• update.json the modified input file

Example

Assume we have the flowing scenario:

> ls -1 $(pwd)
3bfe5e8ee-checksums.zip
723965504-checksums.zip
update.json

> cat update.json
{
  "date": "2021-08-20T13:43:20.024561",
  "latest": "3bfe5e8ee",
  "updates": [
    "723965504"
  ]
}

> echo $(cd $CONTENT; git rev-parse --short HEAD)
c4123a3f1

We now run:

> differy package $BUILD_OUT_ROOT --rev c4123a3f1
packaging update c4123a3f1 → 3bfe5e8ee
packaging update c4123a3f1 → 723965504
building content for c4123a3f1

This will generate:

> ls -1 {c4123a3f1*,update.json}

c4123a3f1-3bfe5e8ee-app-update.zip
c4123a3f1-3bfe5e8ee-diff.json
c4123a3f1-3bfe5e8ee-update.zip
c4123a3f1-723965504-app-update.zip
c4123a3f1-723965504-diff.json
c4123a3f1-723965504-update.zip
c4123a3f1-app-content.zip
c4123a3f1-checksums.zip
c4123a3f1-content.zip
c4123a3f1-content.json
update.json

Automating and Uploading Artifacts

We include a shell script that automates everything we need to generate the latest bundles. And then uploads it to GCS for distribution.

Take a look at scripts/run.sh