# Lono
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Lono is a CloudFormation Template generator. Lono generates CloudFormation templates based on ERB ruby templates in either `yaml` or `json` format.
**UPDATE**: lono now supports yaml format for CloudFormation! The old json format is still supported. For current projects, you do not have to change anything as the format is autodetected as part of `lono generate`.
Newly generated projects with `lono new infra` will use the yaml format by default. If you prefer the json format use `lono new --format json infra`. You cannot mix and match json and yaml format in one project, it's either all json or yaml. If any one has questions feel free to ping me: tongueroo@gmail.com.
## Usage
$ lono new infra
This sets up a starter lono project called infra with example templates. Next you cd into the folder and generate the templates.
$ cd infra
$ lono generate
This generates the templates in the `config` and `templates` folders to the `output` folder.
The starter lono template project config files looks like [this](lib/starter_project_yaml/config/lono.rb) and [this](lib/starter_project_yaml/config/lono/api.rb). Here's a snippet from one of the config files: [config/lono.rb](lib/starter_project_yaml/config/lono.rb).
```ruby
template "api-web-prod.yml" do
app,role,env = name.sub('.yml','').split('-')
source "web.yml.erb"
variables(
env: env,
app: app,
role: role,
ami: "ami-123",
instance_type: "m1.small",
port: "80",
high_threshold: "15",
high_periods: "4",
low_threshold: "5",
low_periods: "10",
max_size: "24",
min_size: "6",
down_adjustment: "-3",
up_adjustment: "3",
ssl_cert: "arn:aws:iam::12345:server-certificate/wildcard"
)
end
```
Here is the corresponding ERB template [templates/web.yml.erb](lib/starter_project_yaml/templates/web.yml.erb). Note that some of the source code has been shorten for brevity.
```yaml
<% @app,@role,@env = name.sub('.yml','').split('-') -%>
---
AWSTemplateFormatVersion: '2010-09-09'
Description: <%= @app.capitalize %> Stack
Mappings:
...
Outputs:
...
Parameters:
Application:
Default: <%= @app %>
Description: Application name
Type: String
...
Resources:
CPUAlarmHigh:
Properties:
AlarmActions:
- Ref: WebServerScaleUpPolicy
AlarmDescription: Scale-up if CPU > <%= @high_threshold %>% for <%= @high_mins %>
...
<%= partial("host_record.yml.erb", domain: "mydomain.com") %>
LaunchConfig:
Properties:
BlockDeviceMappings:
- DeviceName: "/dev/sdb"
VirtualName: ephemeral0
ImageId:
...
UserData:
Fn::Base64: !Sub | # No more Fn::Join needed
#!/bin/bash -lexv
<% stack_name = "#{@env}-#{@app}-#{@role}" %>
exec > >(tee /var/log/user-data.log|logger -t user-data -s 2>/dev/console) 2>&1
echo <%= stack_name %> > /tmp/stack_name
cat /proc/uptime | cut -f1 -d'.' > /tmp/time-to-boot
Type: AWS::AutoScaling::LaunchConfiguration
```
The generated `output/blog-web-prod.yml` CloudFormation template looks like this:
```yaml
---
AWSTemplateFormatVersion: '2010-09-09'
Description: Api Stack
Mappings:
...
Outputs:
...
Parameters:
Application:
Default: api
Description: Application name
Type: String
...
Resources:
CPUAlarmHigh:
Properties:
AlarmActions:
- Ref: WebServerScaleUpPolicy
AlarmDescription: Scale-up if CPU > 15% for
...
HostRecord:
Properties:
Comment: DNS name for mydomain.com
HostedZoneName: ".mydomain.net."
Name:
Fn::Join:
- ''
- - Ref: AWS::StackName
- mydomain.com
ResourceRecords:
- Fn::GetAtt:
- elb
- DNSName
TTL: '60'
Type: CNAME
Type: AWS::Route53::RecordSet
LaunchConfig:
Properties:
BlockDeviceMappings:
- DeviceName: "/dev/sdb"
VirtualName: ephemeral0
ImageId:
...
UserData:
Fn::Base64: |
#!/bin/bash -lexv
exec > >(tee /var/log/user-data.log|logger -t user-data -s 2>/dev/console) 2>&1
echo api-web-prod > /tmp/stack_name
cat /proc/uptime | cut -f1 -d'.' > /tmp/time-to-boot
Type: AWS::AutoScaling::LaunchConfiguration
```
## Template helper methods
There are helper methods that are available in templates.
* partial(relative_path, variables, options) - Can be use to embed other files in a template. The partial view should be placed in the `templates/partial` folder of the project. So:
* partial('launch\_config.json.erb') -> `templates/partial/launch_config.json.erb`
* partial('launch\_config.json.erb', foo: "bar", hello: "world") - variables can be passed to the partial helper method are available to the partial as instance variables. So, in this case `@foo` and `@hello` will be available in the `launch_config.json.erb` partial.
* partial('user_data/bootstrap.sh.erb', {}, indent: 10) - Indent the result partial by 10 spaces. Useful for yaml format.
* user\_data - Helpful if you are using CloudFormation json format. More info on the [wiki page](https://github.com/tongueroo/lono/wiki/user_data-helper-for-json-format).
## Breaking up config/lono.rb
If you have a lot of templates, the config/lono.rb file can get unwieldy long. You can break up the lono.rb file and put template defintions in the config/lono directory. Any file in this directory will be automatically loaded. An [example](lib/starter_project_yaml/config/lono/api.rb) is in the starter project.
## Generate
You can generate the CF templates by running:
$ lono generate
$ lono g -c # shortcut
The lono init command also sets up guard-lono. Guard-lono continuously generates the cloudformation templates. Just run guard.
$ guard
## lono-cfn and lono-params
Running `lono generate` and building up the `aws cloudformation create-stack` command repeatedly gets old. The `lono-cfn` tool will automatically run `lono generate` and then launch the CloudFormation stack all in one command. Example usage:
```
$ lono-cfn create mystack-$(date +%Y%m%d%H%M%S) --template mystack --params mystack
$ lono-cfn create mystack-$(date +%Y%m%d%H%M%S) # shorthand if template and params file matches.
$ lono-cfn update mystack-1493859659
$ lono-cfn delete mystack-1493859659
```
More info about lono-cfn here: [lono-cfn](https://github.com/tongueroo/lono-cfn) - Wrapper cfn tool to quickly create CloudFormation stacks from lono templates and params files.
The params file is formatted with a simple `key=value`, env-like file. It is cleaner to have a `params/mystack.txt` file like so:
```bash
Param1=1
Param2=2
```
Verus the rather verbose standard CloudFormation parameters json file:
```json
[
{
"ParameterKey": "Param1",
"ParameterValue": "1"
},
{
"ParameterKey": "Param2",
"ParameterValue": "2"
}
]
```
More info about lono-parmas here: [lono-params](https://github.com/tongueroo/lono-params) - Tool to generate a CloudFormation parameters json formatted file from a simplier env like file.