389 lines
14 KiB
Markdown
389 lines
14 KiB
Markdown
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# High Availability on AWS
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GitLab on AWS can leverage many of the services that are already
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configurable with High Availability. These services have a lot of
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flexibility and are able to adopt to most companies, best of all is the
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ability to automate both vertical and horizontal scaling.
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In this article we'll go through a basic HA setup where we'll start by
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configuring our Virtual Private Cloud and subnets to later integrate
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services such as RDS for our database server and ElastiCache as a Redis
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cluster to finally manage them within an auto scaling group with custom
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scaling policies.
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***
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## Where to Start
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Login to your AWS account through the `My Account` dropdown on
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`https://aws.amazon.com` or through the URI assigned to your team such as
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`https://myteam.signin.aws.amazon.com/console/`. You'll start on the
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Amazon Web Services console from where we can choose all of the services
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we'll be using to configure our cloud infrastructure.
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***
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## Network
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We'll start by creating a VPC for our GitLab cloud infrastructure, then
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we can create subnets to have public and private instances in at least
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two AZs. Public subnets will require a Route Table keep an associated
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Internet Gateway.
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### VPC
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Start by looking for the VPC option on the web console. Now create a new
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VPC. We can use `10.0.0.0/16` for the CIDR block and leave tenancy as
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default if we don't require dedicated hardware.
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If you're setting up the Elastic File System service then select the VPC
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and from the Actions dropdown choose Edit DNS Hostnames and select Yes.
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### Subnet
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Now let's create some subnets in different Availability Zones. Make sure
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that each subnet is associated the the VPC we just created, that it has
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a distinct VPC and lastly that CIDR blocks don't overlap. This will also
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allow us to enable multi AZ for redundancy.
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We will create private and public subnets to match load balancers and
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RDS instances as well.
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The subnets are listed with their name, AZ and CIDR block:
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* gitlab-public-10.0.0.0 - us-west-2a - 10.0.0.0
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* gitlab-private-10.0.1.0 - us-west-2a - 10.0.1.0
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* gitlab-public-10.0.2.0 - us-west-2b - 10.0.2.0
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* gitlab-private-10.0.3.0 - us-west-2b - 10.0.3.0
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### Route Table
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Up to now all our subnets are private. We need to create a Route Table
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to associate an Internet Gateway. On the same VPC dashboard choose
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Route Tables on the left column and give it a name and associate it to
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our newly created VPC.
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### Internet Gateway
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Now still on the same dashboard head over to Internet Gateways and
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create a new one. After its created pres on the `Attach to VPC` button and
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select our VPC.
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### Configure Subnets
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Go back to the Router Tables screen and select the newly created one,
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press the Routes tab on the bottom section and edit it. We need to add a
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new target which will be our Internet Gateway and have it receive
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traffic from any destination.
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Before leaving this screen select the next tab to the rgiht which is
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Subnet Associations and add our public subnets. If you followed our
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naming convention they should be easy to find.
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***
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## Database with RDS
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For our database server we will use Amazon RDS which offers Multi AZ
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for redundancy. Lets start by creating a subnet group and then we'll
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create the actual RDS instance.
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### Subnet Group
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From the RDS dashboard select Subnet Groups. Lets select our VPC from
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the VPC ID dropdown and at the bottom we can add our private subnets.
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### RDS
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Select the RDS service from the Database section and create a new
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PostgreSQL instance. After choosing between a Production or
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Development instance we'll start with the actual configuration. On the
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image bellow we have the settings for this article but note the
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following two options which are of particular interest for HA:
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1. Multi-AZ-Deployment is recommended as redundancy. Read more at
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[High Availability (Multi-AZ)](http://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/Concepts.MultiAZ.html)
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1. While we chose a General Purpose (SSD) for this article a Provisioned
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IOPS (SSD) is best suited for HA. Read more about it at
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[Storage for Amazon RDS](http://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/CHAP_Storage.html)
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The rest of the setting on this page request a DB identifier, username
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and a master password. We've chosen to use `gitlab-ha`, `gitlab` and a
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very secure password respectively. Keep these in hand for later.
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Make sure to choose our gitlab VPC, our subnet group, not have it public,
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and to leave it to create a new security group. The only additional
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change which will be helpful is the database name for which we can use
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`gitlabhq_production`.
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***
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## ElastiCache
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EC is an in-memory hosted caching solution. Redis maintains its own
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persistance and is used for certain types of application.
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Let's choose the ElastiCache service in the Database section from our
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AWS console. Now lets create a cache subnet group which will be very
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similar to the RDS subnet group. Make sure to select our VPC and its
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private subnets.
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Now press the Launch a Cache Cluster and choose Redis for our
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DB engine. You'll be able to configure details such as replication,
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Multi AZ and node types. The second section will allow us to choose our
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subnet and security group and
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***
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## Network File System
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GitLab requires a shared filesystem such as NFS. The file share(s) will be
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mounted on all application servers. There are a variety of ways to build an
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NFS server on AWS.
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One option is to use a third-party AMI that offers NFS as a service. A [search
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for 'NFS' in the AWS Marketplace](https://aws.amazon.com/marketplace/search/results?x=0&y=0&searchTerms=NFS&page=1&ref_=nav_search_box)
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shows options such as NetApp, SoftNAS and others.
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Another option is to build a simple NFS server using a vanilla Linux server backed
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by AWS Elastic Block Storage (EBS).
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> **Note:** GitLab does not recommend using AWS Elastic File System (EFS). See
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details in [High Availability NFS documentation](../../../administration/high_availability/nfs.md#aws-elastic-file-system)
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***
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## Initiate AMI
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We are going to launch an EC2 instance and bake an image so that we can
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later use it for auto scaling. We'll also take this opportunity to add an
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extension to our RDS through this temporary EC2 instance.
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### EC2 Instance
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Look for the EC2 option and choose to create an instance. We'll need at
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least a t2.medium type and for this article we'll choose an Ubuntu 14.04
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HVM 64-bit. In the Configure Instance section choose our GitLab VPC and
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a public subnet. I'd choose at least 10GB of storage.
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In the security group we'll create a new one considering that we need to
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SSH into the instance and also try it out through http. So let's add the
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http traffic from anywhere and name it something such as
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`gitlab-ec2-security-group`.
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While we wait for it to launch we can allocate an Elastic IP and
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associate it with our new EC2 instance.
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### RDS and Redis Security Group
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After the instance is being created we will navigate to our EC2 security
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groups and add a small change for our EC2 instances to be able to
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connect to RDS. First copy the security group name we just defined,
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namely `gitlab-ec2-security-group`, and edit select the RDS security
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group and edit the inbound rules. Choose the rule type to be PostgreSQL
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and paste the name under source.
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Similar to the above we'll jump to the `gitlab-ec2-security-group` group
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and add a custom TCP rule for port 6379 accessible within itself.
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### Install GitLab
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To connect through SSH you will need to have the `pem` file which you
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chose available and with the correct permissions such as `400`.
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After accessing your server don't forget to update and upgrade your
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packages.
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sudo apt-get update && sudo apt-get upgrade -y
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Then follow installation instructions from
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[GitLab](https://about.gitlab.com/downloads-ee/#ubuntu1404), but before
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running reconfigure we need to make sure all our services are tied down
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so just leave the reconfigure command until after we edit our gitlab.rb
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file.
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### Extension for PostgreSQL
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Connect to your new RDS instance to verify access and to install
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a required extension. We can find the host or endpoint by selecting the
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instance and we just created and after the details drop down we'll find
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it labeled as 'Endpoint'; do remember not to include the colon and port
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number.
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sudo /opt/gitlab/embedded/bin/psql -U gitlab -h <rds-endpoint> -d gitlabhq_production
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psql (9.4.7)
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Type "help" for help.
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gitlab=# CREATE EXTENSION pg_trgm;
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gitlab=# \q
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### Configure GitLab
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While connected to your server edit the `gitlab.rb` file at `/etc/gitlab/gitlab.rb`
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find the `external_url 'http://gitlab.example.com'` option and change it
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to the domain you will be using or the public IP address of the current
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instance to test the configuration.
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For a more detailed description about configuring GitLab read [Configuring GitLab for HA](http://docs.gitlab.com/ee/administration/high_availability/gitlab.html)
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Now look for the GitLab database settings and uncomment as necessary. In
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our current case we'll specify the adapter, encoding, host, db name,
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username, and password.
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gitlab_rails['db_adapter'] = "postgresql"
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gitlab_rails['db_encoding'] = "unicode"
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gitlab_rails['db_database'] = "gitlabhq_production"
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gitlab_rails['db_username'] = "gitlab"
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gitlab_rails['db_password'] = "mypassword"
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gitlab_rails['db_host'] = "<rds-endpoint>"
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Next we only need to configure the Redis section by adding the host and
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uncommenting the port.
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The last configuration step is to [change the default file locations ](http://docs.gitlab.com/ee/administration/high_availability/nfs.html)
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to make the EFS integration easier to manage.
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gitlab_rails['redis_host'] = "<redis-endpoint>"
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gitlab_rails['redis_port'] = 6379
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Finally run reconfigure, you might find it useful to run a check and
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a service status to make sure everything has been setup correctly.
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sudo gitlab-ctl reconfigure
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sudo gitlab-rake gitlab:check
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sudo gitlab-ctl status
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If everything looks good copy the Elastic IP over to your browser and
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test the instance manually.
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### AMI
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After you finish testing your EC2 instance go back to its dashboard and
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while the instance is selected press on the Actions dropdown to choose
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Image -> Create an Image. Give it a name and description and confirm.
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***
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## Load Balancer
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On the same dashboard look for Load Balancer on the left column and press
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the Create button. Choose a classic Load Balancer, our gitlab VPC, not
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internal and make sure its listening for HTTP and HTTPS on port 80.
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Here is a tricky part though, when adding subnets we need to associate
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public subnets instead of the private ones where our instances will
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actually live.
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On the secruity group section let's create a new one named
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`gitlab-loadbalancer-sec-group` and allow both HTTP ad HTTPS traffic
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from anywhere.
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The Load Balancer Health will allow us to indicate where to ping and what
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makes up a healthy or unhealthy instance.
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We won't add the instance on the next session because we'll destroy it
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momentarily as we'll be using the image we where creating. We will keep
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the Enable Cross-Zone and Enable Connection Draining active.
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After we finish creating the Load Balancer we can re visit our Security
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Groups to improve access only through the ELB and any other requirement
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you might have.
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***
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## Auto Scaling Group
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Our AMI should be done by now so we can start working on our Auto
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Scaling Group.
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This option is also available through the EC2 dashboard on the left
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sidebar. Press on the create button. Select the new image on My AMIs and
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give it a `t2.medium` size. To be able to use Elastic File System we need
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to add a script to mount EFS automatically at launch. We'll do this at
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the Advanced Details section where we have a [User Data](http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/user-data.html)
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text area that allows us to add a lot of custom configurations which
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allows you to add a custom script for when launching an instance. Let's
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add the following script to the User Data section:
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#cloud-config
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package_upgrade: true
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packages:
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- nfs-common
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runcmd:
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- mkdir -p /gitlab-data
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- chown ec2-user:ec2-user /gitlab-data
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- echo "$(curl --silent 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
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- mount -a -t nfs
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- sudo gitlab-ctl reconfigure
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On the security group section we can chosse our existing
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`gitlab-ec2-security-group` group which has already been tested.
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After this is launched we are able to start creating our Auto Scaling
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Group. Start by giving it a name and assinging it our VPC and private
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subnets. We also want to always start with two instances and if you
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scroll down to Advanced Details we can choose to receive traffic from ELBs.
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Lets enable that option and select our ELB. We also want to use the ELB's
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health check.
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### Policies
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This is the really great part of Auto Scaling, we get to choose when AWS
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launches new instances and when it removes them. For this group we'll
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scale between 2 and 4 instances where one instance will be added if CPU
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utilization is greater than 60% and one instance is removed if it falls
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to less than 45%. Here are the complete policies:
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You'll notice that after we save this AWS starts launching our two
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instances in different AZs and without a public IP which is exactly what
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we where aiming for.
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***
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## Final Thoughts
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After you're done with the policies section have some fun trying to break
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instances. You should be able to see how the Auto Scaling Group and the
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EC2 screen start bringing them up again.
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High Availability is a very big area, we went mostly through scaling and
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some redundancy options but it might also imply Geographic replication.
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There is a lot of ground yet to cover so have a read through these other
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resources and feel free to open an issue to request additional material.
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* [GitLab High Availability](http://docs.gitlab.com/ce/administration/high_availability/README.html#sts=High Availability)
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* [GitLab Geo](http://docs.gitlab.com/ee/gitlab-geo/README.html)
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