是否可以从 localhost 直接连接到 Heroku 数据库？

Question

如果我有一个 DATABASE_URL，是否可以从 localhost 连接到它？我正在使用以下代码：

db = URI.parse(database_url)
connection = ActiveRecord::Base.establish_connection(
                                                     :adapter  => db.scheme == 'postgres' ? 'postgresql' : db.scheme,
                                                     :host     => db.host,
                                                     :username => db.user,
                                                     :password => db.password,
                                                     :database => db.path[1..-1],
                                                     :encoding => 'utf8'
                                                     )

在我的电脑上运行代码时，我不断收到如下错误：

could not connect to server: Connection timed out
Is the server running on host some_host.amazonaws.com and accepting
    TCP/IP connections on port 5432?

我正在使用相同的代码在 Heroku 上运行的两个应用程序之间共享一个数据库，并且它可以正常工作。这让我相信连接到 Heroku 数据库是受限制的，除非你从 Heroku 主机执行它。这是真的吗？

Answer 1

外部连接确实需要 SSL。可以通过sslmode=require 参数强制底层 postgres 适配器使用 SSL。您可以从 ActiveRecord 连接选项向下传递任意参数，如下所示：

ActiveRecord::Base.establish_connection(
  adapter:  'postgresql', 
  host:     'host', 
  username: 'user', 
  password: 'pass', 
  database: 'database_name', 
  encoding: 'utf-8',
  port:     '5432', # could be a non-standard port
  sslmode:  'require' # force SSL
)

我已经在本地验证了这一点，这里有一个完整的会话显示它有效。请确保您没有输入错误：

heroku pg:credentials yellow -a my-app                                                               Connection info string:
   "dbname=ddbolrs4g89dsi host=ec2-23-21-91-108.compute-1.amazonaws.com port=5432 user=itkdrxzjmwcjtw password=wU-4tT3YbF8AZ3U5kwu-2KYPEX ssl
mode=require"
$ irb
> require 'active_record'
 => true
> ActiveRecord::Base.establish_connection(adapter: 'postgresql', database: 'ddbolrs4g89dsi', host: 'ec2-23-21-91-108.compute-1.amazonaws.com', username: 'itkdrxzjmwcjtw', password: 'wU-4tT3YbF8AZ3U5kwu-2KYPEX', sslmodel: 'require')
 => #<ActiveRecord::ConnectionAdapters::ConnectionPool:0x007f7f9ba6f0f0 @mon_owner=nil, @mon_count=0, @mon_mutex=#<Mutex:0x007f7f9ba6f078>, @spec=#<ActiveRecord::Base::ConnectionSpecification:0x007f7f9ba64150 @config={:adapter=>"postgresql", :database=>"ddbolrs4g89dsi", :host=>"ec2-23-21-91-108.compute-1.amazonaws.com", :username=>"itkdrxzjmwcjtw", :password=>"wU-4tT3YbF8AZ3U5kwu-2KYPEX", :sslmodel=>"require"}, @adapter_method="postgresql_connection">, @reserved_connections={}, @queue=#<MonitorMixin::ConditionVariable:0x007f7f9ba6f000 @monitor=#<ActiveRecord::ConnectionAdapters::ConnectionPool:0x007f7f9ba6f0f0 ...>, @cond=#<ConditionVariable:0x007f7f9ba6efd8 @waiters=[], @waiters_mutex=#<Mutex:0x007f7f9ba6ef88>>>, @timeout=5, @size=5, @connections=[], @automatic_reconnect=true>
> ActiveRecord::Base.connection.execute("SELECT version()").first
 => {"version"=>"PostgreSQL 9.1.4 on x86_64-unknown-linux-gnu, compiled by gcc (Ubuntu 4.4.3-4ubuntu5.1) 4.4.3, 64-bit"} 
> exit
$ # remove db, leaked creds ^
$ heroku addons:remove HEROKU_POSTGRESQL_YELLOW -a my-app --confirm my-app 
Removing HEROKU_POSTGRESQL_YELLOW on my-app... done, v490 (free)

Answer 2

到 postgresql 服务器的外部连接需要 Heroku 上的 SSL。也请查看docs。