我最近从 ruby-aaws gem 转移到 asin gem，它更易于使用和理解。但是，我遇到了一个非常奇怪的问题，它导致特定查询的搜索失败并且仅在 heroku 上。
我的代码如下：
require 'asin'
client = ASIN::Client.instance
client.search(:Keywords => "Shark Tale", :SearchIndex => :UnboxVideo, :ResponseGroup => :ItemAttributes)
当它在我的本地机器上运行时，它完美无缺。但是，当我在 heroku 上运行它时，我看到以下错误日志：
REXML::ParseException: #<NoMethodError: undefined method `[]' for nil:NilClass>
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/rexml/parsers/baseparser.rb:340:in `pull_event'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/rexml/parsers/baseparser.rb:183:in `pull'
/app/vendor/bundle/ruby/2.0.0/gems/crack-0.4.0/lib/crack/xml.rb:203:in `parse'
/app/vendor/bundle/ruby/2.0.0/gems/crack-0.4.0/lib/crack/xml.rb:235:in `parse'
/app/vendor/bundle/ruby/2.0.0/gems/asin-1.1.2/lib/asin/client.rb:375:in `call'
/app/vendor/bundle/ruby/2.0.0/gems/asin-1.1.2/lib/asin/client.rb:197:in `search'
(irb):223:in `irb_binding'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/irb/workspace.rb:86:in `eval'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/irb/workspace.rb:86:in `evaluate'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/irb/context.rb:380:in `evaluate'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/irb.rb:492:in `block (2 levels) in eval_input'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/irb.rb:624:in `signal_status'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/irb.rb:489:in `block in eval_input'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/irb/ruby-lex.rb:247:in `block (2 levels) in each_top_level_statement'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/irb/ruby-lex.rb:233:in `loop'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/irb/ruby-lex.rb:233:in `block in each_top_level_statement'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/irb/ruby-lex.rb:232:in `catch'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/irb/ruby-lex.rb:232:in `each_top_level_statement'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/irb.rb:488:in `eval_input'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/irb.rb:397:in `block in start'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/irb.rb:396:in `catch'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/irb.rb:396:in `start'
/app/vendor/bundle/ruby/2.0.0/gems/railties-3.2.8/lib/rails/commands/console.rb:47:in `start'
/app/vendor/bundle/ruby/2.0.0/gems/railties-3.2.8/lib/rails/commands/console.rb:8:in `start'
/app/vendor/bundle/ruby/2.0.0/gems/railties-3.2.8/lib/rails/commands.rb:41:in `<top (required)>'
script/rails:6:in `require'
script/rails:6:in `<main>'
...
Exception parsing
Line: 1
Position: 30315
Last 80 unconsumed characters:
Actor><Actor>Matthew Broderick</Actor><Actor>Patrick Warburton</Actor><Actor>J
from /app/vendor/ruby-2.0.0/lib/ruby/2.0.0/rexml/parsers/baseparser.rb:439:in `rescue in pull_event'
from /app/vendor/ruby-2.0.0/lib/ruby/2.0.0/rexml/parsers/baseparser.rb:331:in `pull_event'
from /app/vendor/ruby-2.0.0/lib/ruby/2.0.0/rexml/parsers/baseparser.rb:183:in `pull'
from /app/vendor/bundle/ruby/2.0.0/gems/crack-0.4.0/lib/crack/xml.rb:203:in `parse'
from /app/vendor/bundle/ruby/2.0.0/gems/crack-0.4.0/lib/crack/xml.rb:235:in `parse'
from /app/vendor/bundle/ruby/2.0.0/gems/asin-1.1.2/lib/asin/client.rb:375:in `call'
from /app/vendor/bundle/ruby/2.0.0/gems/asin-1.1.2/lib/asin/client.rb:197:in `search'
from (irb):223
from /app/vendor/bundle/ruby/2.0.0/gems/railties-3.2.8/lib/rails/commands/console.rb:47:in `start'
from /app/vendor/bundle/ruby/2.0.0/gems/railties-3.2.8/lib/rails/commands/console.rb:8:in `start'
from /app/vendor/bundle/ruby/2.0.0/gems/railties-3.2.8/lib/rails/commands.rb:41:in `<top (required)>'
from script/rails:6:in `require'
from script/rails:6:in `<main>'
这在 Heroku 上 10 次中大约有 9 次失败。我尝试了一些变体，并且以下一些变体一直成功：
稍微改变查询
client.search(:Keywords => "Shark Tales", :SearchIndex => :UnboxVideo, :ResponseGroup => :ItemAttributes)
更改响应组
client.search(:Keywords => "Shark Tale", :SearchIndex => :UnboxVideo, :ResponseGroup => :Offers)
有谁知道这是什么原因造成的？