Class: ZendeskAPI::Middleware::Request::EtagCache

Inherits:
Faraday::Middleware
  • Object
show all
Defined in:
lib/zendesk_api/middleware/request/etag_cache.rb

Overview

Request middleware that caches responses based on etags can be removed once this is merged: https://github.com/pengwynn/faraday_middleware/pull/42

Instance Method Summary collapse

Constructor Details

#initialize(app, options = {}) ⇒ EtagCache

Returns a new instance of EtagCache.



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# File 'lib/zendesk_api/middleware/request/etag_cache.rb', line 10

def initialize(app, options = {})
  @app = app
  @instrumentation = options[:instrumentation] if options[:instrumentation].respond_to?(:instrument)
  @cache = options[:cache] ||
    raise("need :cache option e.g. ActiveSupport::Cache::MemoryStore.new")
  @cache_key_prefix = options.fetch(:cache_key_prefix, :faraday_etags)
end

Instance Method Details

#cache_key(env) ⇒ Object 



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# File 'lib/zendesk_api/middleware/request/etag_cache.rb', line 18

def cache_key(env)
  [@cache_key_prefix, env[:url].to_s]
end

#call(environment) ⇒ Object 



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# File 'lib/zendesk_api/middleware/request/etag_cache.rb', line 22

def call(environment)
  return @app.call(environment) unless [:get, :head].include?(environment[:method])

  # send known etag
  cached = @cache.read(cache_key(environment))

  if cached
    environment[:request_headers]["If-None-Match"] ||= cached[:response_headers]["Etag"]
  end

  @app.call(environment).on_complete do |env|
    if cached && env[:status] == 304 # not modified
      # Handle differences in serialized env keys in Faraday < 1.0 and 1.0
      # See https://github.com/lostisland/faraday/pull/847
      env[:body] = cached[:body]
      env[:response_body] = cached[:response_body]

      env[:response_headers].merge!(
        etag: cached[:response_headers][:etag],
        content_type: cached[:response_headers][:content_type],
        content_length: cached[:response_headers][:content_length],
        content_encoding: cached[:response_headers][:content_encoding]
      )
      if @instrumentation
        begin
          @instrumentation.instrument("zendesk.cache_hit",
            {
              endpoint: env[:url]&.path,
              status: env[:status]
            })
        rescue
          # Swallow instrumentation errors to maintain cache behavior
        end
      end
    elsif env[:status] == 200 && env[:response_headers]["Etag"] # modified and cacheable
      @cache.write(cache_key(env), env.to_hash)
      if @instrumentation
        begin
          @instrumentation.instrument("zendesk.cache_miss",
            {
              endpoint: env[:url]&.path,
              status: env[:status]
            })
        rescue
          # Swallow instrumentation errors to maintain cache behavior
        end
      end
    end
  end
end