Go Webserver Cookbook for Amazon OpsWorks

We have several Go web applications that we run at http://www.crowdmob.com and wanted to be able to deploy them using Amazon's OpsWorks http://aws.amazon.com/opsworks/ to get auto-scaling and auto-provisioning.

This is the recipe we use which we are using in production. It git clones into a releases/{NOW} directory, builds the app (assuming your main package is defined in a go source file named server.go), symlinks the current directory to it, and tells monit to restart the service representing your server.

Dependencies

This cookbook depends on the following:

• deploy: the base amazon deploy recipe at https://github.com/aws/opsworks-cookbooks/tree/master/deploy
• golang: the installation of go recipe at https://github.com/crowdmob/chef-golang
• monit: the monit package to ensure your server is running, and tries to restart it if not at https://github.com/crowdmob/chef-monit

Only Use 64 Bit EC2 Instances

At this time, the golang cookbook mentioned doesn't dynamically choose the right binary at runtime, based on CPU. That means that it assumes a 64 bit ec2 instance, which is a large instance or better.

Select the Custom Layer Type

When you make your Layer in OpsWorks, be sure to select Other > Custom, rather than "Rails App Server" or some other pre-defined stack.

Custom Chef Recipes Setup

To deploy your app, you'll have to make sure 2 of the recipes in this cookbook are run.

1. nutty::configure should run during the configuration phase of your node in OpsWorks
2. nutty::deploy should run during (every) deployment phase of your node.

Databag Setup

This cookbook relies on a databag, which you should set in Amazon OpsWorks as your Stack's "Custom Chef JSON", with the following parameters:

{
  "service_realm": "production",
  "deploy": {
    "YOUR_APPLICATION_NAME": {
      "application_type": "nutty",
      "env": {
        "AWS_ACCESS_KEY_ID": "YOUR_AWS_ACCESS_KEY_CREDENTIALS",
        "AWS_SECRET_ACCESS_KEY": "YOUR_AWS_SECRET_KEY_CREDENTIALS",
        "AWS_REGION": "us-east-1",
        "PORT": 80
      },
      "kafka": {
        "topics": [ "YOUR_TOPIC_1" ],
        "max_message_size": 4096
      }
    }
  }
}

Here's a little more about the ones you have to fill in:

• YOUR_APPLICATION_NAME is what you named your app, in the "Apps" section of OpsWorks
• YOUR_AWS_ACCESS_KEY_CREDENTIALS should be gotten from Amazon AWS
• YOUR_AWS_SECRET_KEY_CREDENTIALS should also be gotten from Amazon AWS
• YOUR_TOPIC_1 is an array of kafka topics, or empty

Important note: this cookbook double-checks that your application_type is set to nutty (our lite golang web framework). If application_type is not set to nutty, none of the cookbook will run for that app.

How it Works

This cookbook builds and runs a go webapp in the following way:

• The server.go source file is built using go get . followed by go build -o ./nutty_APPNAME_server server.go. That results in an executable of your application at /srv/www/APPNAME/current/nutty_APPNAME_server
• A nutty.properties file is created using your databag and output at /srv/www/APPNAME/shared/config/nutty.properties
• A nutty-APPNAME-server-daemon shell script is created and placed in /srv/www/APPNAME/current/, which handles start and restart commands, by calling /srv/www/APPNAME/current/nutty_APPNAME_server -c /srv/www/APPNAME/shared/config/nutty.properties and outputting logs to /srv/www/APPNAME/shared/log/nutty.log
• A nutty_APPNAME_server.monitrc monit script is created, which utilizes the nutty-APPNAME-server-daemon script for startup and shutdown, and is placed in /etc/monit.d or /etc/monit/conf.d, depending on your OS (defined in the monit cookbook)
• monit is restarted, which incorporates the the new files.

A little about nutty

At CrowdMob, we're working on a lite web framework we're calling nutty.

For the purposes of this cookbook, though, the only thing that it assumes about your webapp is:

1. Your main function is in a file called server.go in the base of your project.
2. Your server.go program won't die if it's sent a -c flag at the command line with a filepath after it, like go run server.go -c /path/to/config.properties. Whether or not it uses that file, however, is up to it.

License and Author

Author:: Matthew Moore

Copyright:: 2013, CrowdMob Inc.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.