Merge branch '22864-kubernetes-deploy-with-terminal' into 'master'

Add online terminal support for Kubernetes

## What does this MR do?

Gives terminal access to kubernetes-deployed environments  via the deployment service

## Are there points in the code the reviewer needs to double check?

## Why was this MR needed?

Part of idea to production

## Screenshots (if relevant)

### `/root/reviewing/environments`

![Screen_Shot_2016-12-15_at_19.10.40](/uploads/bd2c54c07b6c85dec3328a20cd185b64/Screen_Shot_2016-12-15_at_19.10.40.png)

### `/root/reviewing/environments/10013`

![Screen_Shot_2016-12-19_at_12.52.39](/uploads/db4e4e06cda88437e8727433d65898b9/Screen_Shot_2016-12-19_at_12.52.39.png)

### `/root/reviewing/enviroments/10013/terminal`

![Screen_Shot_2016-12-15_at_02.35.52](/uploads/1bb77b7e2de2c657ae3bda62dc4f0970/Screen_Shot_2016-12-15_at_02.35.52.png)

## Does this MR meet the acceptance criteria?

- [x] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) added
- [x] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- Tests
  - [X] Added for this feature/bug
  - [x] All builds are passing
- [X] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [X] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

* Closes #22864 #22958
* Alternative to, and somewhat based on,  !6770 
* Depends on https://gitlab.com/gitlab-org/gitlab-workhorse/merge_requests/83

See merge request !7690

9 files changed, 149 insertions, 11 deletions

diff --git a/doc/README.md b/doc/README.md
index a60a5359540..8bf33cad5e4 100644
--- a/doc/README.md
+++ b/doc/README.md
@@ -34,6 +34,7 @@
 - [Integration](integration/README.md) How to integrate with systems such as JIRA, Redmine, Twitter.
 - [Issue closing pattern](administration/issue_closing_pattern.md) Customize how to close an issue from commit messages.
 - [Koding](administration/integration/koding.md) Set up Koding to use with GitLab.
+- [Online terminals](administration/integration/terminal.md) Provide terminal access to environments from within GitLab.
 - [Libravatar](customization/libravatar.md) Use Libravatar instead of Gravatar for user avatars.
 - [Log system](administration/logs.md) Log system.
 - [Environment Variables](administration/environment_variables.md) to configure GitLab.
diff --git a/doc/administration/high_availability/load_balancer.md b/doc/administration/high_availability/load_balancer.md
index 136f570ac27..e61ea359a6a 100644
--- a/doc/administration/high_availability/load_balancer.md
+++ b/doc/administration/high_availability/load_balancer.md
@@ -10,11 +10,11 @@ you need to use with GitLab.
 
 ## Basic ports
 
-| LB Port | Backend Port | Protocol   |
-| ------- | ------------ | --------   |
-| 80      | 80           | HTTP       |
-| 443     | 443          | HTTPS [^1] |
-| 22      | 22           | TCP        |
+| LB Port | Backend Port | Protocol        |
+| ------- | ------------ | --------------- |
+| 80      | 80           | HTTP  [^1]      |
+| 443     | 443          | HTTPS [^1] [^2] |
+| 22      | 22           | TCP             |
 
 ## GitLab Pages Ports
 
@@ -25,8 +25,8 @@ GitLab Pages requires a separate VIP. Configure DNS to point the
 
 | LB Port | Backend Port | Protocol |
 | ------- | ------------ | -------- |
-| 80      | Varies [^2]  | HTTP     |
-| 443     | Varies [^2]  | TCP [^3] |
+| 80      | Varies [^3]  | HTTP     |
+| 443     | Varies [^3]  | TCP [^4] |
 
 ## Alternate SSH Port
 
@@ -50,13 +50,19 @@ Read more on high-availability configuration:
 1. [Configure NFS](nfs.md)
 1. [Configure the GitLab application servers](gitlab.md)
 
-[^1]: When using HTTPS protocol for port 443, you will need to add an SSL
+[^1]: [Terminal support](../../ci/environments.md#terminal-support) requires
+      your load balancer to correctly handle WebSocket connections. When using
+      HTTP or HTTPS proxying, this means your load balancer must be configured
+      to pass through the `Connection` and `Upgrade` hop-by-hop headers. See the
+      [online terminal](../integration/terminal.md) integration guide for
+      more details.
+[^2]: When using HTTPS protocol for port 443, you will need to add an SSL
       certificate to the load balancers. If you wish to terminate SSL at the
       GitLab application server instead, use TCP protocol.
-[^2]: The backend port for GitLab Pages depends on the
+[^3]: The backend port for GitLab Pages depends on the
       `gitlab_pages['external_http']` and `gitlab_pages['external_https']`
       setting. See [GitLab Pages documentation][gitlab-pages] for more details.
-[^3]: Port 443 for GitLab Pages should always use the TCP protocol. Users can
+[^4]: Port 443 for GitLab Pages should always use the TCP protocol. Users can
       configure custom domains with custom SSL, which would not be possible
       if SSL was terminated at the load balancer.
 
diff --git a/doc/administration/integration/terminal.md b/doc/administration/integration/terminal.md
new file mode 100644
index 00000000000..05d0a97e554
--- /dev/null
+++ b/doc/administration/integration/terminal.md
@@ -0,0 +1,73 @@
+# Online terminals
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7690)
+in GitLab 8.15. Only project masters and owners can access online terminals.
+
+With the introduction of the [Kubernetes](../../project_services/kubernetes.md)
+project service, GitLab gained the ability to store and use credentials for a
+Kubernetes cluster. One of the things it uses these credentials for is providing
+access to [online terminals](../../ci/environments.html#online-terminals)
+for environments.
+
+## How it works
+
+A detailed overview of the architecture of online terminals and how they work
+can be found in [this document](https://gitlab.com/gitlab-org/gitlab-workhorse/blob/master/doc/terminal.md).
+In brief:
+
+* GitLab relies on the user to provide their own Kubernetes credentials, and to
+  appropriately label the pods they create when deploying.
+* When a user navigates to the terminal page for an environment, they are served
+  a JavaScript application that opens a WebSocket connection back to GitLab.
+* The WebSocket is handled in [Workhorse](https://gitlab.com/gitlab-org/gitlab-workhorse),
+   rather than the Rails application server.
+* Workhorse queries Rails for connection details and user permissions; Rails
+  queries Kubernetes for them in the background, using [Sidekiq](../troubleshooting/sidekiq.md)
+* Workhorse acts as a proxy server between the user's browser and the Kubernetes
+  API, passing WebSocket frames between the two.
+* Workhorse regularly polls Rails, terminating the WebSocket connection if the
+  user no longer has permission to access the terminal, or if the connection
+  details have changed.
+
+##  Enabling and disabling terminal support
+
+As online terminals use WebSockets, every HTTP/HTTPS reverse proxy in front of
+Workhorse needs to be configured to pass the `Connection` and `Upgrade` headers
+through to the next one in the chain. If you installed Gitlab using Omnibus, or
+from source, starting with GitLab 8.15, this should be done by the default
+configuration, so there's no need for you to do anything.
+
+However, if you run a [load balancer](../high_availability/load_balancer.md) in
+front of GitLab, you may need to make some changes to your configuration. These
+guides document the necessary steps for a selection of popular reverse proxies:
+
+* [Apache](https://httpd.apache.org/docs/2.4/mod/mod_proxy_wstunnel.html)
+* [NGINX](https://www.nginx.com/blog/websocket-nginx/)
+* [HAProxy](http://blog.haproxy.com/2012/11/07/websockets-load-balancing-with-haproxy/)
+* [Varnish](https://www.varnish-cache.org/docs/4.1/users-guide/vcl-example-websockets.html)
+
+Workhorse won't let WebSocket requests through to non-WebSocket endpoints, so
+it's safe to enable support for these headers globally. If you'd rather had a
+narrower set of rules, you can restrict it to URLs ending with `/terminal.ws`
+(although this may still have a few false positives).
+
+If you installed from source, or have made any configuration changes to your
+Omnibus installation before upgrading to 8.15, you may need to make some
+changes to your configuration. See the  [8.14 to 8.15 upgrade](../../update/8.14-to-8.15.md#nginx-configuration)
+document for more details.
+
+If you'd like to disable online terminal support in GitLab, just stop passing
+the `Connection` and `Upgrade` hop-by-hop headers in the *first* HTTP reverse
+proxy in the chain. For most users, this will be the NGINX server bundled with
+Omnibus Gitlab, in which case, you need to:
+
+* Find the `nginx['proxy_set_headers']` section of your `gitlab.rb` file
+* Ensure the whole block is uncommented, and then comment out or remove the
+  `Connection` and `Upgrade` lines.
+
+For your own load balancer, just reverse the configuration changes recommended
+by the above guides.
+
+When these headers are not passed through, Workhorse will return a
+`400 Bad Request` response to users attempting to use an online terminal. In
+turn, they will receive a `Connection failed` message.
diff --git a/doc/ci/environments.md b/doc/ci/environments.md
index bad0233a9ce..07d92bb746c 100644
--- a/doc/ci/environments.md
+++ b/doc/ci/environments.md
@@ -25,7 +25,9 @@ Environments are like tags for your CI jobs, describing where code gets deployed
 Deployments are created when [jobs] deploy versions of code to environments,
 so every environment can have one or more deployments. GitLab keeps track of
 your deployments, so you always know what is currently being deployed on your
-servers.
+servers. If you have a deployment service such as [Kubernetes][kubernetes-service]
+enabled for your project, you can use it to assist with your deployments, and
+can even access a terminal for your environment from within GitLab!
 
 To better understand how environments and deployments work, let's consider an
 example. We assume that you have already created a project in GitLab and set up
@@ -233,6 +235,46 @@ Remember that if your environment's name is `production` (all lowercase), then
 it will get recorded in [Cycle Analytics](../user/project/cycle_analytics.md).
 Double the benefit!
 
+## Terminal support
+
+>**Note:**
+Terminal support was added in GitLab 8.15 and is only available to project
+masters and owners.
+
+If you deploy to your environments with the help of a deployment service (e.g.,
+the [Kubernetes](../project_services/kubernetes.md) service), GitLab can open
+a terminal session to your environment! This is a very powerful feature that
+allows you to debug issues without leaving the comfort of your web browser. To
+enable it, just follow the instructions given in the service documentation.
+
+Once enabled, your environments will gain a "terminal" button:
+
+![Terminal button on environment index](img/environments_terminal_button_on_index.png)
+
+You can also access the terminal button from the page for a specific environment:
+
+![Terminal button for an environment](img/environments_terminal_button_on_show.png)
+
+Wherever you find it, clicking the button will take you to a separate page to
+establish the terminal session:
+
+![Terminal page](img/environments_terminal_page.png)
+
+This works just like any other terminal - you'll be in the container created
+by your deployment, so you can run shell commands and get responses in real
+time, check the logs, try out configuration or code tweaks, etc. You can open
+multiple terminals to the same environment - they each get their own shell
+session -  and even a multiplexer like `screen` or `tmux`!  
+
+>**Note:**
+Container-based deployments often lack basic tools (like an editor), and may
+be stopped or restarted at any time. If this happens, you will lose all your
+changes! Treat this as a debugging tool, not a comprehensive online IDE. You
+can use [Koding](../administration/integration/koding.md) for online
+development.
+
+---
+
 While this is fine for deploying to some stable environments like staging or
 production, what happens for branches? So far we haven't defined anything
 regarding deployments for branches other than `master`. Dynamic environments
@@ -524,6 +566,7 @@ Below are some links you may find interesting:
 [Pipelines]: pipelines.md
 [jobs]: yaml/README.md#jobs
 [yaml]: yaml/README.md
+[kubernetes-service]: ../project_services/kubernetes.md]
 [environments]: #environments
 [deployments]: #deployments
 [permissions]: ../user/permissions.md
diff --git a/doc/ci/img/environments_terminal_button_on_index.png b/doc/ci/img/environments_terminal_button_on_index.png
new file mode 100644
index 00000000000..6f05b2aa343
--- /dev/null
+++ b/doc/ci/img/environments_terminal_button_on_index.png
diff --git a/doc/ci/img/environments_terminal_button_on_show.png b/doc/ci/img/environments_terminal_button_on_show.png
new file mode 100644
index 00000000000..9469fab99ab
--- /dev/null
+++ b/doc/ci/img/environments_terminal_button_on_show.png
diff --git a/doc/ci/img/environments_terminal_page.png b/doc/ci/img/environments_terminal_page.png
new file mode 100644
index 00000000000..fde1bf325a6
--- /dev/null
+++ b/doc/ci/img/environments_terminal_page.png
diff --git a/doc/project_services/kubernetes.md b/doc/project_services/kubernetes.md
index fda364b864e..0c5c88dd983 100644
--- a/doc/project_services/kubernetes.md
+++ b/doc/project_services/kubernetes.md
@@ -47,3 +47,17 @@ GitLab CI build environment:
 - `KUBE_TOKEN`
 - `KUBE_NAMESPACE`
 - `KUBE_CA_PEM` - only if a custom CA bundle was specified
+
+## Terminal support
+
+>**NOTE:**
+Added in GitLab 8.15. You must be the project owner or have `master` permissions
+to use terminals. Support is currently limited to the first container in the
+first pod of your environment.
+
+When enabled, the Kubernetes service adds online [terminal support](../ci/environments.md#terminal-support)
+to your environments. This is based on the `exec` functionality found in
+Docker and Kubernetes, so you get a new shell session within your existing
+containers. To use this integration, you should deploy to Kubernetes using
+the deployment variables above, ensuring any pods you create are labelled with
+`app=$CI_ENVIRONMENT_SLUG`.
diff --git a/doc/user/permissions.md b/doc/user/permissions.md
index 39fe2409a29..5ada8748d85 100644
--- a/doc/user/permissions.md
+++ b/doc/user/permissions.md
@@ -33,6 +33,7 @@ The following table depicts the various user permission levels in a project.
 | See a container registry              |         | ✓          | ✓           | ✓        | ✓      |
 | See environments                      |         | ✓          | ✓           | ✓        | ✓      |
 | Create new environments               |         |            | ✓           | ✓        | ✓      |
+| Use environment terminals             |         |            |             | ✓        | ✓      |
 | Stop environments                     |         |            | ✓           | ✓        | ✓      |
 | See a list of merge requests          |         | ✓          | ✓           | ✓        | ✓      |
 | Manage/Accept merge requests          |         |            | ✓           | ✓        | ✓      |