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+# High Availability on AWS
+
+GitLab on AWS can leverage many of the services that are already
+configurable with High Availability. These services have a lot of
+flexibility and are able to adopt to most companies, best of all is the
+ability to automate both vertical and horizontal scaling.
+
+In this article we'll go through a basic HA setup where we'll start by
+configuring our Virtual Private Cloud and subnets to later integrate
+services such as RDS for our database server and ElastiCache as a Redis
+cluster to finally manage them within an auto scaling group with custom
+scaling policies.
+
+***
+
+## Where to Start
+
+Login to your AWS account through the `My Account` dropdown on
+`https://aws.amazon.com` or through the URI assigned to your team such as
+`https://myteam.signin.aws.amazon.com/console/`. You'll start on the
+Amazon Web Services console from where we can choose all of the services
+we'll be using to configure our cloud infrastructure.
+
+***
+
+## Network
+
+We'll start by creating a VPC for our GitLab cloud infrastructure, then
+we can create subnets to have public and private instances in at least
+two AZs. Public subnets will require a Route Table keep an associated
+Internet Gateway.
+
+### VPC
+
+Start by looking for the VPC option on the web console. Now create a new
+VPC. We can use `10.0.0.0/16` for the CIDR block and leave tenancy as
+default if we don't require dedicated hardware.
+
+![New VPC](img/new_vpc.png)
+
+If you're setting up the Elastic File System service then select the VPC
+and from the Actions dropdown choose Edit DNS Hostnames and select Yes.
+
+### Subnet
+
+Now let's create some subnets in different Availability Zones. Make sure
+that each subnet is associated the the VPC we just created, that it has
+a distinct VPC and lastly that CIDR blocks don't overlap. This will also
+allow us to enable multi AZ for redundancy.
+
+We will create private and public subnets to match load balancers and
+RDS instances as well.
+
+![Subnet Creation](img/subnet.png)
+
+The subnets are listed with their name, AZ and CIDR block:
+
+* gitlab-public-10.0.0.0  - us-west-2a - 10.0.0.0
+* gitlab-private-10.0.1.0 - us-west-2a - 10.0.1.0
+* gitlab-public-10.0.2.0  - us-west-2b - 10.0.2.0
+* gitlab-private-10.0.3.0 - us-west-2b - 10.0.3.0
+
+### Route Table
+
+Up to now all our subnets are private. We need to create a Route Table
+to associate an Internet Gateway. On the same VPC dashboard choose
+Route Tables on the left column and give it a name and associate it to
+our newly created VPC.
+
+![Route Table](img/route_table.png)
+
+
+### Internet Gateway
+
+Now still on the same dashboard head over to Internet Gateways and
+create a new one. After its created pres on the `Attach to VPC` button and
+select our VPC.
+
+![Internet Gateway](img/ig.png)
+
+### Configure Subnets
+
+Go back to the Router Tables screen and select the newly created one,
+press the Routes tab on the bottom section and edit it. We need to add a
+new target which will be our Internet Gateway and have it receive
+traffic from any destination.
+
+![Subnet Config](img/ig-rt.png)
+
+Before leaving this screen select the next tab to the rgiht which is
+Subnet Associations and add our public subnets. If you followed our
+naming convention they should be easy to find.
+
+***
+
+## Database with RDS
+
+For our database server we will use Amazon RDS which offers Multi AZ
+for redundancy. Lets start by creating a subnet group and then we'll
+create the actual RDS instance.
+
+### Subnet Group
+
+From the RDS dashboard select Subnet Groups. Lets select our VPC from
+the VPC ID dropdown and at the bottom we can add our private subnets.
+
+![Subnet Group](img/db-subnet-group.png)
+
+### RDS
+
+Select the RDS service from the Database section and create a new
+PostgreSQL instance. After choosing between a Production or
+Development instance we'll start with the actual configuration. On the
+image bellow we have the settings for this article but note the
+following two options which are of particular interest for HA:
+
+1. Multi-AZ-Deployment is recommended as redundancy. Read more at
+[High Availability (Multi-AZ)](http://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/Concepts.MultiAZ.html)
+1. While we chose a General Purpose (SSD) for this article a Provisioned
+IOPS (SSD) is best suited for HA. Read more about it at
+[Storage for Amazon RDS](http://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/CHAP_Storage.html)
+
+![RDS Instance Specs](img/instance_specs.png)
+
+The rest of the setting on this page request a DB identifier, username
+and a master password. We've chosen to use `gitlab-ha`, `gitlab` and a
+very secure password respectively. Keep these in hand for later.
+
+![Network and Security](img/rds-net-opt.png)
+
+Make sure to choose our gitlab VPC, our subnet group, not have it public,
+and to leave it to create a new security group. The only additional
+change which will be helpful is the database name for which we can use
+`gitlabhq_production`.
+
+***
+
+## ElastiCache
+
+EC is an in-memory hosted caching solution. Redis maintains its own
+persistance and is used for certain types of application.
+
+Let's choose the ElastiCache service in the Database section from our
+AWS console. Now lets create a cache subnet group which will be very
+similar to the RDS subnet group. Make sure to select our VPC and its
+private subnets.
+
+![ElastiCache](img/ec-subnet.png)
+
+Now press the Launch a Cache Cluster and choose Redis for our
+DB engine. You'll be able to configure details such as replication,
+Multi AZ and node types. The second section will allow us to choose our
+subnet and security group and     
+
+![Redis Cluster details](img/redis-cluster-det.png)
+
+![Redis Network](img/redis-net.png)
+
+***
+
+## Elastic File System
+
+This new AWS offering allows us to create a file system accessible by

+EC2 instances within a VPC. Choose our VPC and the subnets will be
+
automatically configured assuming we don't need to set explicit IPs.
+The
next section allows us to add tags and choose between General
+Purpose or
Max I/O which is a good option when being accessed by a
+large number of
EC2 instances.
+
+

![Elastic File System](img/elastic-file-system.png)
+
+To actually mount and install the NFS client we'll use the User Data
+section when adding our Launch Configuration.
+
+***
+
+## Initiate AMI
+
+We are going to launch an EC2 instance and bake an image so that we can
+later use it for auto scaling. We'll also take this opportunity to add an
+extension to our RDS through this temporary EC2 instance.
+
+### EC2 Instance
+
+Look for the EC2 option and choose to create an instance. We'll need at
+least a t2.medium type and for this article we'll choose an Ubuntu 14.04
+HVM 64-bit. In the Configure Instance section choose our GitLab VPC and
+a public subnet. I'd choose at least 10GB of storage.
+
+In the security group we'll create a new one considering that we need to
+SSH into the instance and also try it out through http. So let's add the
+http traffic from anywhere and name it something such as
+`gitlab-ec2-security-group`.
+
+While we wait for it to launch we can allocate an Elastic IP and
+associate it with our new EC2 instance.  
+
+### RDS and Redis Security Group
+
+After the instance is being created we will navigate to our EC2 security
+groups and add a small change for our EC2 instances to be able to
+connect to RDS. First copy the security group name we just defined,
+namely `gitlab-ec2-security-group`, and edit select the RDS security
+group and edit the inbound rules. Choose the rule type to be PostgreSQL
+and paste the name under source.
+
+![RDS security group](img/rds-sec-group.png)
+
+Similar to the above we'll jump to the `gitlab-ec2-security-group` group
+and add a custom TCP rule for port 6379 accessible within itself.
+
+### Install GitLab
+
+To connect through SSH you will need to have the `pem` file which you
+chose available and with the correct permissions such as `400`.
+
+After accessing your server don't forget to update and upgrade your
+packages.
+
+    sudo apt-get update && sudo apt-get upgrade -y
+
+Then follow installation instructions from
+[GitLab](https://about.gitlab.com/downloads-ee/#ubuntu1404), but before
+running reconfigure we need to make sure all our services are tied down
+so just leave the reconfigure command until after we edit our gitlab.rb
+file.
+
+
+### Extension for PostgreSQL
+
+Connect to your new RDS instance to verify access and to install
+a required extension. We can find the host or endpoint by selecting the
+instance and  we just created and after the details drop down we'll find
+it labeled as 'Endpoint'; do remember not to include the colon and port
+number.
+
+    sudo /opt/gitlab/embedded/bin/psql -U gitlab -h <rds-endpoint> -d gitlabhq_production
+    psql (9.4.7)
+    Type "help" for help.
+
+    gitlab=# CREATE EXTENSION pg_trgm;
+    gitlab=# \q
+
+### Configure GitLab
+
+While connected to your server edit the `gitlab.rb` file at `/etc/gitlab/gitlab.rb`
+find the `external_url 'http://gitlab.example.com'` option and change it
+to the domain you will be using or the public IP address of the current
+instance to test the configuration.
+
+For a more detailed description about configuring GitLab read [Configuring GitLab for HA](http://docs.gitlab.com/ee/administration/high_availability/gitlab.html)
+
+Now look for the GitLab database settings and uncomment as necessary. In
+our current case we'll specify the adapter, encoding, host, db name,
+username, and password.
+
+    gitlab_rails['db_adapter'] = "postgresql"
+    gitlab_rails['db_encoding'] = "unicode"    
+    gitlab_rails['db_database'] = "gitlabhq_production"   
+    gitlab_rails['db_username'] = "gitlab"
+    gitlab_rails['db_password'] = "mypassword"
+    gitlab_rails['db_host'] = "<rds-endpoint>"
+
+Next we only need to configure the Redis section by adding the host and
+uncommenting the port.
+
+
+
+The last configuration step is to [change the default file locations ](http://docs.gitlab.com/ee/administration/high_availability/nfs.html)
+to make the EFS integration easier to manage.
+
+    gitlab_rails['redis_host'] = "<redis-endpoint>"
+    gitlab_rails['redis_port'] = 6379
+
+Finally run reconfigure, you might find it useful to run a check and
+a service status to make sure everything has been setup correctly.
+
+    sudo gitlab-ctl reconfigure  
+    sudo gitlab-rake gitlab:check  
+    sudo gitlab-ctl status  
+
+If everything looks good copy the Elastic IP over to your browser and
+test the instance manually.
+
+### AMI
+
+After you finish testing your EC2 instance go back to its dashboard and
+while the instance is selected press on the Actions dropdown to choose
+Image -> Create an Image. Give it a name and description and confirm.
+
+***
+
+## Load Balancer
+
+On the same dashboard look for Load Balancer on the left column and press
+the Create button. Choose a classic Load Balancer, our gitlab VPC, not
+internal and make sure its listening for HTTP and HTTPS on port 80.
+
+Here is a tricky part though, when adding subnets we need to associate
+public subnets instead of the private ones where our instances will
+actually live.
+
+On the secruity group section let's create a new one named
+`gitlab-loadbalancer-sec-group` and allow both HTTP ad HTTPS traffic
+from anywhere.
+
+The Load Balancer Health will allow us to indicate where to ping and what
+makes up a healthy or unhealthy instance.
+
+We won't add the instance on the next session because we'll destroy it
+momentarily as we'll be using the image we where creating. We will keep
+the Enable Cross-Zone and Enable Connection Draining active.
+
+After we finish creating the Load Balancer we can re visit our Security
+Groups to improve access only through the ELB and any other requirement
+you might have.
+
+***
+
+## Auto Scaling Group
+
+Our AMI should be done by now so we can start working on our Auto
+Scaling Group.
+
+This option is also available through the EC2 dashboard on the left
+sidebar. Press on the create button. Select the new image on My AMIs and
+give it a `t2.medium` size. To be able to use Elastic File System we need
+to add a script to mount EFS automatically at launch. We'll do this at
+the Advanced Details section where we have a [User Data](http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/user-data.html)
+text area that allows us to add a lot of custom configurations which
+allows you to add a custom script for when launching an instance. Let's
+add the following script to the User Data section:
+
+
+    #cloud-config
+    package_upgrade: true
+    packages:
+    - nfs-common
+    runcmd:
+    - mkdir -p /gitlab-data
+    - chown ec2-user:ec2-user /gitlab-data
+    - echo "$(curl -s http://169.254.169.254/latest/meta-data/placement/availability-zone).file-system-id.aws-region.amazonaws.com:/ /gitlab-data nfs defaults,vers=4.1 0 0" >> /etc/fstab
+    - mount -a -t nfs
+    - sudo gitlab-ctl reconfigure
+
+On the security group section we can chosse our existing
+`gitlab-ec2-security-group` group which has already been tested.
+
+After this is launched we are able to start creating our Auto Scaling
+Group. Start by giving it a name and assinging it our VPC and private
+subnets. We also want to always start with two instances and if you
+scroll down to Advanced Details we can choose to receive traffic from ELBs.
+Lets enable that option and select our ELB. We also want to use the ELB's
+health check.
+
+![Auto scaling](img/auto-scaling-det.png)
+
+### Policies
+
+This is the really great part of Auto Scaling, we get to choose when AWS
+launches new instances and when it removes them. For this group we'll
+scale between 2 and 4 instances where one instance will be added if CPU
+utilization is greater than 60% and one instance is removed if it falls
+to less than 45%. Here are the complete policies:
+
+![Policies](img/policies.png)
+
+You'll notice that after we save this AWS starts launching our two
+instances in different AZs and without a public IP which is exactly what
+we where aiming for.
+
+***
+
+## Final Thoughts
+
+After you're done with the policies section have some fun trying to break
+instances. You should be able to see how the Auto Scaling Group and the
+EC2 screen start bringing them up again.
+
+High Availability is a very big area, we went mostly through scaling and
+some redundancy options but it might also imply Geographic replication.
+There is a lot of ground yet to cover so have a read through these other
+resources and feel free to open an issue to request additional material.
+
+ * [GitLab High Availability](http://docs.gitlab.com/ce/administration/high_availability/README.html#sts=High Availability)
+ * [GitLab Geo](http://docs.gitlab.com/ee/gitlab-geo/README.html)