Merge branch 'ci/build-artifacts-documentation' into 'master'

Add basic documentation for build artifacts

/cc @axil @ayufan 

See merge request !2511

doc/README.md

@@ -30,6 +30,7 @@
 - [User permissions](ci/permissions/README.md)
 - [API](ci/api/README.md)
 - [Triggering builds through the API](ci/triggers/README.md)
+- [Build artifacts](ci/build_artifacts/README.md)
 
 ### CI Languages
 

doc/ci/README.md

@@ -12,6 +12,7 @@
 * [Using Variables](variables/README.md)
 * [Using SSH keys](ssh_keys/README.md)
 * [Triggering builds through the API](triggers/README.md)
+* [Build artifacts](build_artifacts/README.md)
 
 ### Languages
 

doc/ci/build_artifacts/README.md

+# Introduction to build artifacts
+
+Artifacts is a list of files and directories which are attached to a build
+after it completes successfully.
+
+Since GitLab 8.2 and [GitLab Runner] 0.7.0, build artifacts that are created by
+GitLab Runner are uploaded to GitLab and are downloadable as a single archive
+(`tar.gz`) using the GitLab UI.
+
+Starting from GitLab 8.4 and GitLab Runner 1.0, the artifacts archive format
+changed to `ZIP`, and it is now possible to browse its contents, with the added
+ability of downloading the files separately.
+
+## Enabling build artifacts
+
+If you are searching for ways to use the artifacts feature, jump to
+[Defining artifacts in `.gitlab-ci.yml`](#defining-artifacts-in-gitlab-ciyml).
+
+The artifacts feature is enabled by default in all GitLab installations.
+
+If by any chance you want to disable the artifacts feature on your GitLab
+instance, follow the steps below.
+
+---
+
+**In Omnibus installations:**
+
+1. Edit `/etc/gitlab/gitlab.rb` and add the following line:
+
+    ```ruby
+    gitlab_rails['artifacts_enabled'] = false
+    ```
+
+1. Save the file and [reconfigure GitLab][] for the changes to take effect.
+
+---
+
+**In installations from source:**
+
+1. Edit `/home/git/gitlab/config/gitlab.yml` and add or amend the following lines:
+
+    ```yaml
+    artifacts:
+      enabled: false
+    ```
+
+1. Save the file and [restart GitLab][] for the changes to take effect.
+
+## Defining artifacts in `.gitlab-ci.yml`
+
+A simple example of using the artifacts definition in `.gitlab-ci.yml` would be
+the following:
+
+```yaml
+pdf:
+  script: xelatex mycv.tex
+  artifacts:
+    paths:
+    - mycv.pdf
+```
+
+A job named `pdf` calls the `xelatex` command in order to build a pdf file from
+the latex source file `mycv.tex`. We then define the `artifacts` paths which in
+turn are defined with the `paths` keyword. All paths to files and directories
+are relative to the repository that was cloned during the build.
+
+For more examples on artifacts, follow the
+[separate artifacts yaml documentation](../yaml/README.md#artifacts).
+
+## Storing build artifacts
+
+After a successful build, GitLab Runner uploads an archive containing the build
+artifacts to GitLab.
+
+To change the location where the artifacts are stored, follow the steps below.
+
+---
+
+**In Omnibus installations:**
+
+_The artifacts are stored by default in
+`/var/opt/gitlab/gitlab-rails/shared/artifacts`._
+
+1. To change the storage path for example to `/mnt/storage/artifacts`, edit
+   `/etc/gitlab/gitlab.rb` and add the following line:
+
+    ```ruby
+    gitlab_rails['artifacts_path'] = "/mnt/storage/artifacts"
+    ```
+
+1. Save the file and [reconfigure GitLab][] for the changes to take effect.
+
+---
+
+**In installations from source:**
+
+_The artifacts are stored by default in
+`/home/git/gitlab/shared/artifacts`._
+
+1. To change the storage path for example to `/mnt/storage/artifacts`, edit
+   `/home/git/gitlab/config/gitlab.yml` and add or amend the following lines:
+
+    ```yaml
+    artifacts:
+      enabled: true
+      path: /mnt/storage/artifacts
+    ```
+
+1. Save the file and [restart GitLab][] for the changes to take effect.
+
+## Browsing build artifacts
+
+When GitLab receives an artifacts archive, an archive metadata file is also
+generated. This metadata file describes all the entries that are located in the
+artifacts archive itself. The metadata file is in a binary format, with
+additional GZIP compression.
+
+GitLab does not extract the artifacts archive in order to save space, memory
+and disk I/O. It instead inspects the metadata file which contains all the
+relevant information. This is especially important when there is a lot of
+artifacts, or an archive is a very large file.
+
+---
+
+After a successful build, if you visit the build's specific page, you can see
+that there are two buttons.
+
+One is for downloading the artifacts archive and the other for browsing its
+contents.
+
+![Build artifacts browser button](img/build_artifacts_browser_button.png)
+
+---
+
+The archive browser shows the name and the actual file size of each file in the
+archive. If your artifacts contained directories, then you are also able to
+browse inside them.
+
+Below you can see an image of three different file formats, as well as two
+directories.
+
+![Build artifacts browser](img/build_artifacts_browser.png)
+
+---
+
+## Downloading build artifacts
+
+If you need to download the whole archive, there are buttons in various places
+inside GitLab that make that possible.
+
+1. While on the builds page, you can see the download icon for each build's
+   artifacts archive in the right corner
+
+1. While inside a specific build, you are presented with a download button
+   along with the one that browses the archive
+
+1. And finally, when browsing and archive you can see the download button at
+   the top right corner
+
+---
+
+Note that GitLab does not extract the entire artifacts archive to send just a
+single file to the user.
+
+When clicking on a specific file, [GitLab Workhorse] extracts it from the
+archive and the download begins.
+
+This implementation saves space, memory and disk I/O.
+
+[gitlab runner]: https://gitlab.com/gitlab-org/gitlab-ci-multi-runner "GitLab Runner repository"
+[reconfigure gitlab]: ../../administration/restart_gitlab.md "How to restart GitLab documentation"
+[restart gitlab]: ../../administration/restart_gitlab.md "How to restart GitLab documentation"
+[gitlab workhorse]: https://gitlab.com/gitlab-org/gitlab-workhorse "GitLab Workhorse repository"