1# The Stackage data flow
3The Stackage project is really built on top of a number of different
4subcomponents. This page covers how they fit together. The Stackage data flow
5diagram gives a good bird's-eye view:
7
11There are three inputs into the data flow:
13* [Hackage](http://hackage.haskell.org/) is the upstream repository of all
14 available open source Haskell packages that are part of our ecosystem.
15 Hackage provides both cabal file metadata (via the 00-index.tar file) and
16 tarballs of the individual packages.
18* [build-constraints.yaml](https://github.com/commercialhaskell/stackage/blob/master/build-constraints.yaml)
19 is the primary Stackage input file. This is where package maintainers can add
20 packages to the Stackage package set. This also defines upper bounds, skipped
21 tests, and a few other pieces of metadata.
23* [stackage-content](https://github.com/fpco/stackage-content) is a Github
24 repository containing static file content served from stackage.org
29reasons](https://tech.fpcomplete.com/blog/2015/05/distributing-packages-without-sysadmin),
30we leverage Travis CI for running some processes. In particular:
32* [all-cabal-files](https://github.com/commercialhaskell/all-cabal-files/blob/hackage/.travis.yml)
33 clones all cabal files from Hackage's 00-index.tar file into a Git repository
34 without any modification
36* [all-cabal-hashes](https://github.com/commercialhaskell/all-cabal-hashes/blob/hackage/.travis.yml)
37 is mostly the same, but also includes cryptographic hashes of the package
38 tarballs for more secure download (as leveraged by
39 [Stack](http://haskellstack.com). It is powered by [all-cabal-hashes-tool](https://github.com/commercialhaskell/all-cabal-hashes-tool)
41* [all-cabal-packages](https://github.com/commercialhaskell/all-cabal-packages)
42 uses [hackage-mirror](http://github.com/fpco/hackage-mirror) to populate the
43 hackage.fpcomplete.com mirror of Hackage, which provides S3-backed high
44 availability hosting of all package tarballs
46* [all-cabal-metadata](https://github.com/commercialhaskell/all-cabal-metadata)
48 [all-cabal-metadata-tool](https://github.com/commercialhaskell/all-cabal-metadata-tool)
49 to query extra metadata from Hackage about packages and put them into YAML
50 files. As we'll see later, this avoids the need to make a lot of costly calls
53Travis does not currently provide a means of running jobs on a regular basis.
54Therefore, we have a simple cron job on the Stackage build server that triggers
55each of the above builds every 30 minutes.
59The heart of running Stackage builds is the
60[stackage-curator](https://github.com/fpco/stackage-curator) tool. We run this
61on a daily basis on the Stackage build server for Stackage Nightly, and on a
62weekly basis for LTS Haskell. The build process is [highly
63automated](https://github.com/commercialhaskell/stackage/blob/master/automated/build.sh) and
64leverages Docker quite a bit.
66stackage-curator needs to know about the most recent versions of all packages,
67their tarball contents, and some metadata, all of which it gets from the
68Travis-generated sources mentioned in the previous section. In addition, it
69needs to know about build constraints, which can come from one of two places:
71* When doing an LTS Haskell minor version bump (e.g., building lts-5.13), it
72 grabs the previous version (e.g., lts-5.12) and converts the previous package
73 set into constraints. For example, if lts-5.12 contains the package foo-5.6.7,
74 this will be converted into the constraint `foo >= 5.6.7 && < 5.7`.
75* When doing a Stackage Nightly build or LTS Haskell major version bump (e.g.,
76 building lts-6.0), it grabs the latest version of the build-constraints.yaml
79By combining these constraints with the current package data, stackage-curator
80can generate a build plan and check it. (As an aside, this build plan
81generation and checking also occurs every time you make a pull request to the
82stackage repo.) If there are version bounds problems, one of the [Stackage
83curators](https://github.com/commercialhaskell/stackage/blob/master/CURATORS.md) will open
84up a Github issue and will add upper bounds, temporarily block a package, or
85some other corrective action.
87Once a valid build plan is found, stackage-curator will build all packages,
88build docs, and run test suites. Assuming that all succeeds, it generates some
91* Uploads the build plan as a YAML file to either
92 [stackage-nightly](https://github.com/fpco/stackage-nightly) or
93 [lts-haskell](https://github.com/fpco/lts-haskell)
94* Uploads the generated Haddock docs and a package index (containing all used
95 .cabal files) to haddock.stackage.org.
97## stackage-server-cron
99On the Stackage build server, we run the [stackage-server-cron
100executable](https://github.com/fpco/stackage-server/blob/master/app/stackage-server-cron.hs)
101regularly, which generates:
104 database](https://github.com/fpco/stackage-server/blob/master/Stackage/Database.hs)
105 containing information on snapshots, the packages they contain, Hackage
106 metadata about packages, and a bit more. This database is uploaded to S3.
107* A Hoogle database for each snapshot, which is also uploaded to S3
111The [software running stackage.org](https://github.com/fpco/stackage-server) is
112a relatively simple Yesod web application. It pulls data from the
113stackage-content repo, the SQLite database, the Hoogle databases, and the build
114plans for Stackage Nightly and LTS Haskell. It doesn't generate anything
115important of its own except for a user interface.
119[Stack](http://haskellstack.com) takes advantage of many of the pieces listed above as well:
121* It by default uses the all-cabal-hashes repo for getting package metadata,
122 and downloads package contents from the hackage.fpcomplete.com mirror (using
123 the hashes in the repo for verification)
124* There are some metadata files in stackage-content which contain information
125 on, for example, where to download GHC tarballs from to make `stack setup`
127* Stack downloads the raw build plans for Stackage Nightly and LTS Haskell from
128 the Github repo and uses them when deciding which packages to build for a
129 given stack.yaml file
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