如何使用Ruby v2.0的AWS SDK检查simpleDB域是否存在

Question

当使用Ruby v1.0的AWS SDK时，检查simpleDB域是否存在很简单:

def domain_exists?(domain_name)
  sdb =  AWS::SimpleDB.new
  domain = sdb.domains[domain_name]
  domain.exists?
end

然而，使用Ruby的AWS SDK v2.0就不再可能了。如何使用v2.0检查simpleDB域是否存在?

Answer 1

有两种方法。

1. 使用domain_metadata并捕获异常。

   def domain_exists?(domain_name)
     sdb = Aws::SimpleDB::Client.new
     sdb.domain_metadata(domain_name: domain_name)
     return true
   rescue Aws::SimpleDB::Errors::NoSuchDomain 
     return false
   end
   

2. 重新打开Aws::SimpleDB::Client类，增加一个使用list_domains的递归方法domain_exists?

   class Aws::SimpleDB::Client
     def domain_exists?(domain_name, limit = 100, next_token=nil)
       resp = list_domains(next_token: next_token, max_number_of_domains: limit)
       domain_exists = resp.domain_names.include?(domain_name)
       return domain_exists if domain_exists # found the domain
       return domain_exists if resp.next_token.nil? # no more domains to search
       domain_exists?(domain_name, limit, resp.next_token) # more domains to search
     end
   end
   

   然后就变得很简单了:

   def domain_exists?(domain_name, limit = 100)
      sdb = Aws::SimpleDB::Client.new
      sdb.domain_exists?(domain_name, limit)
   end