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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 -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'] = "" + +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'] = "" + 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. 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