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Project: Vcr 1.7.1

Rack

VCR provides a rack middleware that uses a cassette for the duration of
a request. Simply provide VCR::Middleware::Rack with a block that sets
the cassette name and options. You can set these based on the rack env
if your block accepts two arguments.

This is useful in a couple different ways:

  • In a rails app, you could use this to log all HTTP API calls made by the rails app (using the :all record mode). Of course, this will only record HTTP API calls made in the request-response cycle--API calls that are offloaded to a background job will not be logged.
  • This can be used as middleware in a simple rack HTTP proxy, to record and replay the proxied requests.
Background
Given
a file named "remote_server.rb" with:
require 'vcr_cucumber_helpers'

request_count = 0
start_sinatra_app(:port => 7777) do
  get('/:path') { "Hello #{params[:path]} #{request_count += 1}" }
end
And
a file named "client.rb" with:
require 'remote_server'
require 'proxy_server'
require 'cgi'

url = URI.parse("http://localhost:8888?url=#{CGI.escape('http://localhost:7777/foo')}")

puts "Response 1: #{Net::HTTP.get_response(url).body}"
puts "Response 2: #{Net::HTTP.get_response(url).body}"
And
the directory "cassettes" does not exist
Scenarios
Use VCR rack middleware to record HTTP responses for a simple rack proxy app
Given
a file named "proxy_server.rb" with:
require 'vcr'

start_sinatra_app(:port => 8888) do
  use VCR::Middleware::Rack do |cassette|
    cassette.name    'proxied'
    cassette.options :record => :new_episodes
  end

  get('/') { Net::HTTP.get_response(URI.parse(params[:url])).body }
end

VCR.config do |c|
  c.cassette_library_dir = 'cassettes'
  c.stub_with :fakeweb
  c.allow_http_connections_when_no_cassette = true
end
When
I run "ruby client.rb"
Then
the output should contain:
Response 1: Hello foo 1
Response 2: Hello foo 1
And
the file "cassettes/proxied.yml" should contain "body: Hello foo 1"
Set cassette name based on rack request env
Given
a file named "proxy_server.rb" with:
require 'vcr'

start_sinatra_app(:port => 8888) do
  use VCR::Middleware::Rack do |cassette, env|
    cassette.name    env['SERVER_NAME']
    cassette.options :record => :new_episodes
  end

  get('/') { Net::HTTP.get_response(URI.parse(params[:url])).body }
end

VCR.config do |c|
  c.cassette_library_dir = 'cassettes'
  c.stub_with :fakeweb
  c.allow_http_connections_when_no_cassette = true
end
When
I run "ruby client.rb"
Then
the output should contain:
Response 1: Hello foo 1
Response 2: Hello foo 1
And
the file "cassettes/localhost.yml" should contain "body: Hello foo 1"

Last published about 2 years ago by myronmarston.