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 APPNAME.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

Additionally, you must use Godep for storing code dependencies.

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. golang::install should run during the setup phase of your node in OpsWorks
2. goapp::configure should run during the configuration phase of your node in OpsWorks
3. goapp::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:

{
  "deploy": {
    "YOUR_APPLICATION_NAME": {
      "application_type": "goapp",
      "gofile": "my_app.go",
      "test_url": "/",
      "env": {
        "PORT": 80,
        "or_whatever": "you want in YOUR_APPLICATION_NAME.properties"
      },
      "config": ["other"]
    }
  },
  "other": {
    "option1": "value1"
  }
}

Important note: this cookbook double-checks that your application_type is set to goapp. If application_type is not set to goapp, none of the cookbook will run for that app. If gofile is omitted, uses APPLICATION_NAME.go. test_url will be tested by monit to ensure server is still up (default "/").

If you include a layers key, only matching layer will deploy this application. E.g.

{
  "deploy": {
    "blog": {
      "application_type": "goapp",
      "layers": ["blog-server"]
    }
  }
}

The blog app will only deploy onto the blog-server layer.

If you include a config key, the matching root-level values will be copied to the properties file as sections, allowing other cookbook configuration to be made available to your application. e.g.

{
  "deploy": {
    "blog": {
      "config": ["wordpress"],
    }
  },
  "wordpress": {
    "database": "db.host"
  }
}

The resulting blog.properties file will contain the following sections:

[wordpress]
database=db.host

How it Works

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

• The APPNAME.go source file is built using go get . followed by go build -o ./goapp_APPNAME_server server.go. That results in an executable of your application at /srv/www/APPNAME/current/goapp_APPNAME_server
• A APPNAME.properties file is created using your databag and output at /srv/www/APPNAME/shared/config/APPNAME.properties
• A goapp-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/goapp_APPNAME_server -c /srv/www/APPNAME/shared/config/APPNAME.properties and outputting logs to /srv/www/APPNAME/shared/log/goapp.log
• A goapp_APPNAME_server.monitrc monit script is created, which utilizes the goapp-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 goapp

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 APPNAME.go in the base of your project.
2. Your APPNAME.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/server.properties. Whether or not it uses that file, however, is up to it.

License and Author

Author:: Matthew Moore, Geoff Hayes

Copyright:: 2013

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.