activejob参数写入opentelemetry的attribute

取值策略

• 基本类型都转成String吧
• activerecord对象，键取model名，值取主键值（[[activerecord的id]]）
• Hash要展平
• Array内如果都是同一类型，不需展开，否则展开

使用case..when..

• 优点：可以自定义优先级
• 缺点：条件判断不太优雅

调用方式

before_perform do |job|
  IndexedArgs.create({ 'job.args' => job.arguments })
  ::Tracer.add_attrs(attrs) if attrs.present?
end

实现

module IndexedArgs
  class << self
    def create(arg)
      case arg
      when nil
        {}
      when String, Integer, Float, BigDecimal, TrueClass, FalseClass
        { nil => arg.to_s }
      when ActiveRecord::Base
        { arg.class.name.underscore.gsub('/', '.') => arg.id }
      # when GlobalID::Identification
      #   { nil => arg.to_global_id.to_s }
      when Array
        create_from_hash(arg.each_with_index.to_h.invert)
      when Hash
        create_from_hash(arg)
      else
        {}
      end
    end

    AVAILABLE_KEY_TYPES = [String, Symbol, Integer]

    def create_from_hash(h)
      h.each_with_object({}) do |(k, v), hash|
        next unless AVAILABLE_KEY_TYPES.any?{ |t| k.is_a?(t) }

        create(v).each_pair do |sub_k, sub_v|
          key = sub_k.present? ? "#{k}.#{sub_k}" : k.to_s
          hash[key] = sub_v
        end
      end
    end
  end
end

使用duck-typing

• 优点：符合ruby玩法，比较优雅
• 缺点：优先级不明确

调用方式

before_perform do |job|
  attrs = { 'job.args' => job.arguments }.indexed_args
  ::Tracer.add_attrs(attrs) if attrs.present?
end

实现

module IndexedArgs
  PRIMITIVE_TYPES = [String, Integer, Float, BigDecimal, TrueClass, FalseClass]

  PRIMITIVE_TYPES.each do |k|
    k.define_method(:indexed_args){ { nil => to_s } }
  end

  module ::ActiveRecord
    class Base
      def indexed_args
        { self.class.name.underscore.gsub('/', '.') => id }
      end
    end
  end

  class ::Array
    def indexed_args
      if all?{ |e| PRIMITIVE_TYPES.any?{ |t| e.is_a?(t) } }
        { nil => map(&:to_s) }
      else
        each_with_index.to_h.invert.indexed_args
      end
    end
  end

  class ::Hash
    INDEXABLE_KEY_TYPES = [String, Symbol, Integer]

    def indexed_args
      each_with_object({}) do |(k, v), hash|
        next unless INDEXABLE_KEY_TYPES.any?{ |t| k.is_a?(t) }

        v.indexed_args.each_pair do |sub_k, sub_v|
          key = sub_k.present? ? "#{k}.#{sub_k}" : k.to_s
          hash[key] = sub_v
        end
      end
    end
  end

  class ::Object
    def indexed_args
      {}
    end
  end
end

写入时机

在after_enqueue和before_perform都写入，这样就能根据job_id和参数查到入队和出队的足迹

class ApplicationJob < ActiveJob::Base
  [:after_enqueue, :before_perform].each do |callback|
    send(callback) do |job|
      if job.arguments.present?
        attrs = { 'messaging.active_job.args' => job.arguments }.indexed_args
        ::Tracer.add_attrs(attrs) if attrs.present?
      end
    end
  end
end