The Lamdera package server

packages.lamdera.io answers the requests the Elm compiler makes to package.elm-lang.org, at the same paths, from a mirror of every published Elm package. The Lamdera compiler uses it by default, so installing packages does not depend on package.elm-lang.org or on GitHub being up, or on a repository still being where it was when the package was published.

It holds 3041 packages, 17008 versions, of which 10234 have their zip here (versions published for Elm 0.18 and earlier have none, there either). 688 are rerouted, 208 are unavailable and 122 packages were renamed.

How it gets packages

• Every hour it asks package.elm-lang.org for versions published since the last time, and fetches each one's elm.json, docs.json and the zip, which it keeps only when its SHA-1 matches the one package.elm-lang.org recorded, as the compiler checks.
• A version published a minute ago is fetched when someone first asks for it, so it works straight away.
• Published versions never change, so once a version is here it stays as it is, whatever happens to its repository.
• When a version's zip is gone or changed on GitHub, a copy recovered from somewhere else is served instead, with what we checked about it. See reroutes.
• Nothing is published here. lamdera publish and elm publish both publish to package.elm-lang.org, and the new version shows up here within the hour.

Using it

The Lamdera compiler uses packages.lamdera.io unless told otherwise:

• LAMDERA_PACKAGE_SERVER=<url> uses another package server, such as a mirror of your own, or https://package.elm-lang.org.
• If packages.lamdera.io does not answer, the compiler says so in one line and uses package.elm-lang.org for the rest of that run.
• A rerouted version that we verified is used with a one-line notice. One we could not verify is only used once you approve it:

• lamdera make --auto-approve-package-rerouting approves rerouted versions for that run,
• LAMDERA_AUTO_APPROVE_PACKAGE_REROUTING=1 does the same for every run in that environment,
• LAMDERA_CACHE=off skips the Lamdera package server altogether: packages come from package.elm-lang.org and GitHub only, as with elm, and a rerouted version then fails to download.

Packages are downloaded into ELM_HOME once, as with elm, so you are only ever asked about a version once.

The API

The same paths as package.elm-lang.org, so anything that reads that can read this:

• /all-packages, /all-packages/since/<n> (GET or POST)
• /packages/<author>/<project>/releases.json
• /packages/<author>/<project>/<version>/elm.json, docs.json, README.md
• /packages/<author>/<project>/<version>/endpoint.json: points at the zip here, and says so when it is a reroute
• /search.json: every package that works with Elm 0.19.1, with its summary, license and latest version
• /reroutes.json: the reroutes, unavailable versions and renamed packages

Downloading everything

The whole mirror is also at cache.lamdera.com/elm: an append-only index.tsv of every version mirrored, and weekly snapshots (snapshots/latest.json) to fill a package cache in one download.

This site

The pages are package.elm-lang.org's, by Evan Czaplicki (BSD-3-Clause), rendered on the server by an elm-pages app, with notes added where the Lamdera package server differs from package.elm-lang.org.