Class: Kube::Templates::Builder

Inherits:
Object
  • Object
show all
Defined in:
lib/kube/templates/builder.rb

Overview

Applies a template of a kubernetes configuration with options for resque workers and builds out deployments for all workers

Example

Given a kubernetes deployment configuration template:

# resque-template.yaml
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: resque-${NAME}
spec:
  replicas: ${REPLICAS}
  template:
    metadata:
      labels:
        service: rails
        app: my-app
        purpose: worker
        queues: ${QUEUES}
    spec:
      containers:
      - name: my-app
        image: us.gcr.io/project-id-1138/my-app-resque:latest
        env:
        - name: QUEUE
          value: ${QUEUES}

And the following worker configuration

# resque-workers.yml
defaults:
  replicas: 2
workers:
  - queues: reports
    replicas: 4
    name: builder
  - queues: process_priority,process

Use the ‘resque-k8s` command to create a series of YAML deployments for kubernetes to consume. Then use `kubectl apply` command to configure the cluster.

$ resque-k8s | kubectl apply -f -

Instance Method Summary collapse

Constructor Details

#initialize(template_file, config_file) ⇒ Builder

Create a template handler for the template and configuration.

template_file The name or IO of the file that has the kubernetes deployment template. config_file The name or IO of the file that has the resque configuration.

For either argument you can provide the path to the template file or you can provide an ‘IO` object for the `Builder` to read. With an `IO` object you are responsible for closing the stream.

Examples:

Kube::Templates::Builder.new("resque-template.yml", "resque-workers.yml")

File.open("resque-template.yml") do |template|
  File.open("resque-workers.yml") do |config|
    Kube::Templates::Builder.new(template, config))
  end
end

Note that if you want to provide a string value to the ‘Builder` you can just use a `StringIO` instance.

Kube::Templates::Builder.new(StringIO.new(template), StringIO.new(config))



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# File 'lib/kube/templates/builder.rb', line 74

def initialize(template_file, config_file)
  @template = readfile(template_file)
  @config   = YAML.load(readfile(config_file))
end

Instance Method Details

#build ⇒ Object

Returns a string of YAML configurations, concatenated with “—” line, for each configuration defined.

The ‘config_file` must have a “workers” property which is a collection of properties that are applied to the template. Template variables are case insensitive, but configuration keys must all be lower case.

You can also provide a “defaults” section that applies default values for any worker that does not have a specific value defined.

There is a special $NAME property that you can use in your template. If not provided as a value, it will default to, roughly, the values for the worker concatenated with “-”.

Example:

# resque-workers.yml
defaults:
  replicas: 2
workers:
  - queues: reports
    replicas: 4
    name: builder
  - queues: process_priority,process

For this configuration, ‘#build` would create two YAML configurations. The first assigns these values in the template:

${QUEUES}   = "reports"
${REPLICAS} = 4
${NAME}     = "builder"

The second assigns these values in the template:

${QUEUES}   = "process_priority,process"
${REPLICAS} = 2
${NAME}     = "process-priority-process"

Configurations are returned in the order defined in the ‘config_file`.



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# File 'lib/kube/templates/builder.rb', line 114

def build
  defaults = @config["defaults"] || {}
  configs = @config["workers"].map do |worker|
    # TODO: We should #downcase the keys for the variables as well
    variables = defaults.merge(worker)
    @template.gsub(/\$\{([^}]+)\}/) do |match|
      key = Regexp.last_match[1].downcase
      if variables.key? key
        variables[key]
      elsif key == "name"
        # NB This doesn't handle utf-8 characters at all
        name_from_values(worker.values)
      else
        match
      end
    end
  end

  configs.join("---\n")
end