postgresql Heroku 上偶尔出现 Postgres 错误：无法将主机名“<pg URL>”转换为地址：名称或服务未知（PG::Error）

Occasional Postgres error on Heroku: could not translate host name "<pg URL>" to address: Name or service not known (PG::Error)

提问by ckbhodge

I'm using the shared postgres (dev / free) plan right now on Heroku and I see this error in my logs a decent amount. Connecting to the PG database does usually work though, so I'm not sure if this is something that's within my control. The Heroku Status page does not list any downtime for the shared databases when these occur.

我现在在 Heroku 上使用共享 postgres（开发/免费）计划，我在日志中看到了相当多的错误。不过，连接到 PG 数据库通常是有效的，所以我不确定这是否在我的控制范围内。当这些发生时，Heroku 状态页面不会列出共享数据库的任何停机时间。

Using Rails 3.1.1 and the Unicorn web server.

使用 Rails 3.1.1 和Unicorn Web 服务器。

Error:could not translate host name "pg60.sharedpg.heroku.com (http://pg60.sharedpg.heroku.com)" to address: Name or service not known (PG::Error)

错误：无法将主机名“pg60.sharedpg.heroku.com（http://pg60.sharedpg.heroku.com）”转换为地址：名称或服务未知（PG::Error）

My Unicornconfig file (after looking around at the recommended settings for Unicorn in Heroku):

我的Unicorn配置文件（在查看 Heroku 中 Unicorn 的推荐设置之后）：

worker_processes 3 # amount of unicorn workers to spin up
timeout 30         # restarts workers that hang for 30 seconds
preload_app true

before_fork do |server, worker|
  # Replace with MongoDB or whatever
  if defined?(ActiveRecord::Base)
    ActiveRecord::Base.connection_handler.clear_all_connections!
    ActiveRecord::Base.connection.disconnect!
    Rails.logger.info('Disconnected from ActiveRecord')
  end

  # If you are using Redis but not Resque, change this
  if defined?(Resque)
    Resque.redis.quit
    Rails.logger.info('Disconnected from Redis')
  end
end

after_fork do |server, worker|
  # Replace with MongoDB or whatever
  if defined?(ActiveRecord::Base)
    ActiveRecord::Base.establish_connection
    ActiveRecord::Base.connection_handler.verify_active_connections!
    Rails.logger.info('Connected to ActiveRecord')
  end

  # If you are using Redis but not Resque, change this
  if defined?(Resque)
    Resque.redis = ENV['REDIS_URI']
    Rails.logger.info('Connected to Redis')
  end
end

Trace:

痕迹：

 328 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - /app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.1.1/lib/active_record/connection_adapters/postgresql_adapter.rb:1032:in `initialize': could not translate host name "pg60.sharedpg.heroku.com (http://pg60.sharedpg.heroku.com)" to address: Name or service not known (PG::Error)
219 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.1.1/lib/active_record/connection_adapters/postgresql_adapter.rb:1032:in `new'
223 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.1.1/lib/active_record/connection_adapters/postgresql_adapter.rb:1032:in `connect'
225 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.1.1/lib/active_record/connection_adapters/postgresql_adapter.rb:301:in `initialize'
217 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.1.1/lib/active_record/connection_adapters/postgresql_adapter.rb:28:in `new'
235 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.1.1/lib/active_record/connection_adapters/postgresql_adapter.rb:28:in `postgresql_connection'

328 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - /app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.1.1/lib/active_record/connection_adapters/postgresql_adapter.rb:1032:in `initialize': could not translate host name "pg60.sharedpg.heroku.com (http://pg60.sharedpg.heroku.com)" to address: Name or service not known (PG::Error)
219 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.1.1/lib/active_record/connection_adapters/postgresql_adapter.rb:1032:in `new'
223 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.1.1/lib/active_record/connection_adapters/postgresql_adapter.rb:1032:in `connect'
225 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.1.1/lib/active_record/connection_adapters/postgresql_adapter.rb:301:in `initialize'
217 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.1.1/lib/active_record/connection_adapters/postgresql_adapter.rb:28:in `new'
235 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.1.1/lib/active_record/connection_adapters/postgresql_adapter.rb:28:in `postgresql_connection'
235 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.1.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:304:in `new_connection'
244 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.1.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:323:in `checkout_new_connection'
249 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.1.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:265:in `block (2 levels) in checkout'
225 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.1.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:261:in `loop'
238 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.1.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:261:in `block in checkout'
153 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /usr/local/lib/ruby/1.9.1/monitor.rb:201:in `mon_synchronize'
229 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.1.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:260:in `checkout'
231 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.1.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:162:in `connection'
240 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.1.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:409:in `retrieve_connection'
249 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.1.1/lib/active_record/connection_adapters/abstract/connection_specification.rb:107:in `retrieve_connection'
239 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.1.1/lib/active_record/connection_adapters/abstract/connection_specification.rb:89:in `connection'
194 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.1.1/lib/active_record/base.rb:703:in `table_exists?'
128 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/app.rb:38:in `<top (required)>'
116 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from config.ru:9 (http://config.ru:9):in `require'
124 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from config.ru:9 (http://config.ru:9):in `block in <main>'
179 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/vendor/bundle/ruby/1.9.1/gems/rack-1.4.1/lib/rack/builder.rb:51:in `instance_eval'
176 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/vendor/bundle/ruby/1.9.1/gems/rack-1.4.1/lib/rack/builder.rb:51:in `initialize'
112 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from config.ru:1 (http://config.ru:1):in `new'
115 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from config.ru:1 (http://config.ru:1):in `<main>'
168 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/vendor/bundle/ruby/1.9.1/gems/unicorn-4.2.0/lib/unicorn.rb:44:in `eval'
180 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/vendor/bundle/ruby/1.9.1/gems/unicorn-4.2.0/lib/unicorn.rb:44:in `block in builder'
181 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/vendor/bundle/ruby/1.9.1/gems/unicorn-4.2.0/lib/unicorn/http_server.rb:691:in `call'
187 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/vendor/bundle/ruby/1.9.1/gems/unicorn-4.2.0/lib/unicorn/http_server.rb:691:in `build_app!'
182 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/vendor/bundle/ruby/1.9.1/gems/unicorn-4.2.0/lib/unicorn/http_server.rb:136:in `start'
178 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/vendor/bundle/ruby/1.9.1/gems/unicorn-4.2.0/bin/unicorn:121:in `<top (required)>'
146 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/vendor/bundle/ruby/1.9.1/bin/unicorn:19:in `load'
148 <13>1 2012-08-27T21:36:37+00:00 d.4122435c-cb44-421a-9a7d-a68bb10457d6 app web.1 (http://web.1) - - from /app/vendor/bundle/ruby/1.9.1/bin/unicorn:19:in `<main>' 

采纳答案by Craig Ringer

That's a DNSerror. It's exceedingly unlikely to be anything to do with your code. If both your Rails app and your DB are within Heroku, contact Heroku support.

那是DNS错误。它极不可能与您的代码有关。如果您的 Rails 应用程序和数据库都在 Heroku 中，请联系 Heroku 支持。

If your Rails app is running outsidethe Heroku cloud (as a bit of searching for the term "Unicorn" suggests it could be; please link to things like this; not everyone knows what "unicorn" is), you need to do some debugging to work out where the DNS issues are. Is it the recursive DNS server your app is using? Some closer caching server? Some intermediate server up the chain used to resolve Heroku's DNS (unlikely) ? Heroku's DNS its self? Is it a packet loss issue, an issue where the server responds with a false negative, one bad server in a round-robin cluster, ... ? Expect to spend lots of quality time with dig +traceand with tracerouteor mtr- assuming you can sshin. If you have root, tcpdumpand tsharkmay also be useful, as will examination of the logs of the DNS server you're using if you can get access to them.

如果您的 Rails 应用程序在 Heroku 云之外运行（搜索“独角兽”一词表明可能是这样；请链接到这样的内容；不是每个人都知道“独角兽”是什么），您需要进行一些调试找出 DNS 问题所在。它是您的应用程序使用的递归 DNS 服务器吗？一些更接近的缓存服务器？一些中间服务器用于解析 Heroku 的 DNS（不太可能）？Heroku 的 DNS 本身？这是一个丢包问题，一个服务器以假阴性响应的问题，一个循环集群中的一个坏服务器，......？期望dig +trace与tracerouteor一起度过很多美好的时光mtr- 假设您可以通过ssh进入。如果您有 root，tcpdump并且tshark如果您可以访问它们，那么检查您正在使用的 DNS 服务器的日志也可能很有用。

If you have no shell access you pretty much have to bug the support of the people you're hosting with.

如果您没有 shell 访问权限，那么您几乎不得不寻求与您一起托管的人的支持。

回答by grokpot

Just for reference, I had the same problem (Heroku was having an issue with AWS). Here was the helpful response from customer service (08/15):

仅供参考，我遇到了同样的问题（Heroku 遇到了 AWS 问题）。以下是客户服务 (08/15) 的有用回复：

We are occasionally seeing DNS resolution failure on our instances and we're working to solve this with AWS. The issue is really intermittent and unfortunately we're having hard time trying to identify the cause. While we're investigating, I have one workaround for this issue - currently, you're using Django's default way for the database connection - which is trying to make a new connection per request. This is pretty expensive, also this means you'll need to do DNS resolution for your every request which would increase the possibility to face this issue very unfortunately. Instead, I recommend that you use connection pooling. You can find some examples here:

https://devcenter.heroku.com/articles/python-concurrency-and-database-connections

One customer who was seeing this issue occasionally (but frequently, with Django app) saw a good improvement with the connection pooling, this should help a lot to prevent it from happening.

我们偶尔会在我们的实例上看到 DNS 解析失败，我们正在努力使用 AWS 解决这个问题。该问题确实是间歇性的，不幸的是，我们很难找出原因。在我们进行调查时，我有一个解决此问题的方法 - 目前，您使用 Django 的默认数据库连接方式 - 尝试为每个请求建立一个新连接。这非常昂贵，这也意味着您需要为每个请求进行 DNS 解析，这将增加非常不幸地面临此问题的可能性。相反，我建议您使用连接池。你可以在这里找到一些例子：

https://devcenter.heroku.com/articles/python-concurrency-and-database-connections

一位偶尔（但经常使用 Django 应用程序）看到此问题的客户发现连接池有了很好的改进，这应该有助于防止它发生。