为什么我会收到“没有听众”的消息？在 Oracle 中使用 Rails 时出错？

Question

我使用 Rails 2.3.5 和 Oracle 10 作为数据库，使用 "oracle_adapter" 和 ruby​​-oci8 连接到 Oracle 主机。

我得到这个异常：

Completed in 463ms (View: 18, DB: 166) | 200 OK [http://192.168.30.128/auctions?page=1]
/!\ FAILSAFE /!\  Mon Feb 01 19:02:11 +0800 2010
  Status: 500 Internal Server Error
  ORA-12541: TNS:no listener
    env.c:257:in oci8lib.so
    /home/qichunren/.gem/ruby/1.8/gems/ruby-oci8-1.0.7/lib/oci8.rb:229:in `initialize'
    /home/qichunren/.gem/ruby/1.8/gems/activerecord-oracle-adapter-1.0.0.9250/lib/active_record/connection_adapters/oracle_adapter.rb:623:in `new'
    /home/qichunren/.gem/ruby/1.8/gems/activerecord-oracle-adapter-1.0.0.9250/lib/active_record/connection_adapters/oracle_adapter.rb:623:in `new_connection'
    /home/qichunren/.gem/ruby/1.8/gems/activerecord-oracle-adapter-1.0.0.9250/lib/active_record/connection_adapters/oracle_adapter.rb:659:in `initialize'
    /home/qichunren/.gem/ruby/1.8/gems/activerecord-oracle-adapter-1.0.0.9250/lib/active_record/connection_adapters/oracle_adapter.rb:35:in `new'
    /home/qichunren/.gem/ruby/1.8/gems/activerecord-oracle-adapter-1.0.0.9250/lib/active_record/connection_adapters/oracle_adapter.rb:35:in `oracle_connection'
    /home/qichunren/.gem/ruby/1.8/gems/activerecord-2.3.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:223:in `send'
    /home/qichunren/.gem/ruby/1.8/gems/activerecord-2.3.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:223:in `new_connection'
    /home/qichunren/.gem/ruby/1.8/gems/activerecord-2.3.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:245:in `checkout_new_connection'
    /home/qichunren/.gem/ruby/1.8/gems/activerecord-2.3.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:188:in `checkout'
    /home/qichunren/.gem/ruby/1.8/gems/activerecord-2.3.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:184:in `loop'
    /home/qichunren/.gem/ruby/1.8/gems/activerecord-2.3.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:184:in `checkout'
    /usr/local/ruby187/lib/ruby/1.8/monitor.rb:242:in `synchronize'
    /home/qichunren/.gem/ruby/1.8/gems/activerecord-2.3.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:183:in `checkout'
    /home/qichunren/.gem/ruby/1.8/gems/activerecord-2.3.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:98:in `connection'
    /home/qichunren/.gem/ruby/1.8/gems/activerecord-2.3.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:326:in `retrieve_connection'
    /home/qichunren/.gem/ruby/1.8/gems/activerecord-2.3.5/lib/active_record/connection_adapters/abstract/connection_specification.rb:123:in `retrieve_connection'
    /home/qichunren/.gem/ruby/1.8/gems/activerecord-2.3.5/lib/active_record/connection_adapters/abstract/connection_specification.rb:115:in `connection'
    /home/qichunren/.gem/ruby/1.8/gems/activerecord-2.3.5/lib/active_record/query_cache.rb:9:in `cache'
    /home/qichunren/.gem/ruby/1.8/gems/activerecord-2.3.5/lib/active_record/query_cache.rb:28:in `call'
    /home/qichunren/.gem/ruby/1.8/gems/activerecord-2.3.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:361:in `call'
    /home/qichunren/.gem/ruby/1.8/gems/actionpack-2.3.5/lib/action_controller/string_coercion.rb:25:in `call'
    /home/qichunren/.gem/ruby/1.8/gems/rack-1.0.1/lib/rack/head.rb:9:in `call'
    /home/qichunren/.gem/ruby/1.8/gems/rack-1.0.1/lib/rack/methodoverride.rb:24:in `call'
    /home/qichunren/.gem/ruby/1.8/gems/actionpack-2.3.5/lib/action_controller/params_parser.rb:15:in `call'
    /home/qichunren/.gem/ruby/1.8/gems/actionpack-2.3.5/lib/action_controller/session/cookie_store.rb:93:in `call'
    /home/qichunren/.gem/ruby/1.8/gems/actionpack-2.3.5/lib/action_controller/failsafe.rb:26:in `call'
    /home/qichunren/.gem/ruby/1.8/gems/rack-1.0.1/lib/rack/lock.rb:11:in `call'
    /home/qichunren/.gem/ruby/1.8/gems/rack-1.0.1/lib/rack/lock.rb:11:in `synchronize'
    /home/qichunren/.gem/ruby/1.8/gems/rack-1.0.1/lib/rack/lock.rb:11:in `call'
    /home/qichunren/.gem/ruby/1.8/gems/actionpack-2.3.5/lib/action_controller/dispatcher.rb:114:in `call'
    /home/qichunren/.gem/ruby/1.8/gems/actionpack-2.3.5/lib/action_controller/reloader.rb:34:in `run'
    /home/qichunren/.gem/ruby/1.8/gems/actionpack-2.3.5/lib/action_controller/dispatcher.rb:108:in `call'
    /home/qichunren/.gem/ruby/1.8/gems/actionpack-2.3.5/lib/action_controller/cgi_process.rb:44:in `dispatch_cgi'
    /home/qichunren/.gem/ruby/1.8/gems/actionpack-2.3.5/lib/action_controller/dispatcher.rb:101:in `dispatch_cgi'
    /home/qichunren/.gem/ruby/1.8/gems/actionpack-2.3.5/lib/action_controller/dispatcher.rb:27:in `dispatch'
    /home/qichunren/.gem/ruby/1.8/gems/mongrel-1.1.5/bin/../lib/mongrel/rails.rb:76:in `process'
    /home/qichunren/.gem/ruby/1.8/gems/mongrel-1.1.5/bin/../lib/mongrel/rails.rb:74:in `synchronize'
    /home/qichunren/.gem/ruby/1.8/gems/mongrel-1.1.5/bin/../lib/mongrel/rails.rb:74:in `process'
    /home/qichunren/.gem/ruby/1.8/gems/mongrel-1.1.5/bin/../lib/mongrel.rb:159:in `process_client'
    /home/qichunren/.gem/ruby/1.8/gems/mongrel-1.1.5/bin/../lib/mongrel.rb:158:in `each'
    /home/qichunren/.gem/ruby/1.8/gems/mongrel-1.1.5/bin/../lib/mongrel.rb:158:in `process_client'
    /home/qichunren/.gem/ruby/1.8/gems/mongrel-1.1.5/bin/../lib/mongrel.rb:285:in `run'
    /home/qichunren/.gem/ruby/1.8/gems/mongrel-1.1.5/bin/../lib/mongrel.rb:285:in `initialize'
    /home/qichunren/.gem/ruby/1.8/gems/mongrel-1.1.5/bin/../lib/mongrel.rb:285:in `new'
    /home/qichunren/.gem/ruby/1.8/gems/mongrel-1.1.5/bin/../lib/mongrel.rb:285:in `run'
    /home/qichunren/.gem/ruby/1.8/gems/mongrel-1.1.5/bin/../lib/mongrel.rb:268:in `initialize'
    /home/qichunren/.gem/ruby/1.8/gems/mongrel-1.1.5/bin/../lib/mongrel.rb:268:in `new'
    /home/qichunren/.gem/ruby/1.8/gems/mongrel-1.1.5/bin/../lib/mongrel.rb:268:in `run'
    /home/qichunren/.gem/ruby/1.8/gems/mongrel-1.1.5/bin/../lib/mongrel/configurator.rb:282:in `run'
    /home/qichunren/.gem/ruby/1.8/gems/mongrel-1.1.5/bin/../lib/mongrel/configurator.rb:281:in `each'
    /home/qichunren/.gem/ruby/1.8/gems/mongrel-1.1.5/bin/../lib/mongrel/configurator.rb:281:in `run'
    /home/qichunren/.gem/ruby/1.8/gems/mongrel-1.1.5/bin/mongrel_rails:128:in `run'
    /home/qichunren/.gem/ruby/1.8/gems/mongrel-1.1.5/bin/../lib/mongrel/command.rb:212:in `run'
    /home/qichunren/.gem/ruby/1.8/gems/mongrel-1.1.5/bin/mongrel_rails:281
    /home/qichunren/.gem/ruby/1.8/bin/mongrel_rails:19:in `load'
    /home/qichunren/.gem/ruby/1.8/bin/mongrel_rails:19

似乎与 Oracle 的连接经常断开。它显示oracle错误：**ORA-12541：TNS：无侦听器**。

我该如何解决这个问题？

oci8.c:270:in oci8lib.so: ORA-12541: TNS:no listener (OCIError)
        from /opt/ruby-enterprise-1.8.7/lib/ruby/gems/1.8/gems/activerecord-oracle_enhanced-adapter-1.2.4/lib/active_record/connec                                                                         tion_adapters/oracle_enhanced_oci_connection.rb:223:in `new'
        from /opt/ruby-enterprise-1.8.7/lib/ruby/gems/1.8/gems/activerecord-oracle_enhanced-adapter-1.2.4/lib/active_record/connec                                                                         tion_adapters/oracle_enhanced_oci_connection.rb:223:in `new_connection'
        from /opt/ruby-enterprise-1.8.7/lib/ruby/gems/1.8/gems/activerecord-oracle_enhanced-adapter-1.2.4/lib/active_record/connec                                                                         tion_adapters/oracle_enhanced_oci_connection.rb:328:in `initialize'
        from /opt/ruby-enterprise-1.8.7/lib/ruby/gems/1.8/gems/activerecord-oracle_enhanced-adapter-1.2.4/lib/active_record/connec                                                                         tion_adapters/oracle_enhanced_oci_connection.rb:24:in `new'
        from /opt/ruby-enterprise-1.8.7/lib/ruby/gems/1.8/gems/activerecord-oracle_enhanced-adapter-1.2.4/lib/active_record/connec                                                                         tion_adapters/oracle_enhanced_oci_connection.rb:24:in `initialize'
        from /opt/ruby-enterprise-1.8.7/lib/ruby/gems/1.8/gems/activerecord-oracle_enhanced-adapter-1.2.4/lib/active_record/connec                                                                         tion_adapters/oracle_enhanced_connection.rb:9:in `new'
        from /opt/ruby-enterprise-1.8.7/lib/ruby/gems/1.8/gems/activerecord-oracle_enhanced-adapter-1.2.4/lib/active_record/connec                                                                         tion_adapters/oracle_enhanced_connection.rb:9:in `create'
        from /opt/ruby-enterprise-1.8.7/lib/ruby/gems/1.8/gems/activerecord-oracle_enhanced-adapter-1.2.4/lib/active_record/connec                                                                         tion_adapters/oracle_enhanced_adapter.rb:50:in `oracle_enhanced_connection'
        from /opt/ruby-enterprise-1.8.7/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/connection_adapters/abstract/c                                                                         onnection_specification.rb:291:in `send'
        from /opt/ruby-enterprise-1.8.7/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/connection_adapters/abstract/c                                                                         onnection_specification.rb:291:in `connection='
        from /opt/ruby-enterprise-1.8.7/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/connection_adapters/abstract/c                                                                         onnection_specification.rb:259:in `retrieve_connection'
        from /opt/ruby-enterprise-1.8.7/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/connection_adapters/abstract/c                                                                         onnection_specification.rb:78:in `connection'
        from /opt/ruby-enterprise-1.8.7/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/base.rb:2438:in `quoted_table_                                                                         name'
        from /opt/ruby-enterprise-1.8.7/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/base.rb:1259:in `find_one'
        from /opt/ruby-enterprise-1.8.7/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/base.rb:1250:in `find_from_ids                                                                         '
        from /opt/ruby-enterprise-1.8.7/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/base.rb:504:in `find'
        from script/maintenance/adjust_settlement.rb:19

Answer 1

首先，您应该使用 oracle_enhanced 适配器，因为不再支持原始的 oracle 适配器。我还建议使用最新的 ruby-oci8 版本 2.0.3。还要检查您使用的是哪个 Oracle 客户端版本 - 我推荐 Oracle Instant Client 10.2.0.4 或更高版本

但是，如果您收到 ORA-12541: TNS:no Listener 错误，则问题可能出在与数据库的网络连接或 Oracle 服务器端的某些问题。但请尝试 oracle_enhanced 适配器和最新的 ruby​​-oci8 版本，并告诉它是否可以解决您的问题。

Answer 2

确保：

• 您在 ${ORACLE_HOME}/network/admin/tnsnames.ora 中正确设置了连接名称。
• 您可以在加载 oci8 驱动程序之前设置 ORACLE_HOME。

如果这不起作用，请显式指定主机[:端口]/sid 作为数据库名称。

例如，如果您的主机是mydbhost.myorg.org，端口号是1522，sid是employeedb，您可以使用以下命令：

database: mydbhost.myorg.org:1522/employeedb

如果您的端口是默认的1521，则可以省略冒号和端口号。

Answer 3

我认为您的监听器由于没有活动而超时。我怀疑您正在打开连接，发出查询，然后在代码空闲等待另一个客户端请求时保持连接打开。如果您的数据库设置为允许永久连接，但这可能会耗尽所有池，这是大多数站点不希望的。

您可以调整数据库以允许更长的会话，或者告诉它根本不要断开连接，或者修改代码以在尝试发送查询之前检查连接，必要时重新连接，然后继续。

并非所有数据库适配器都允许您执行保持活动/心跳，甚至询问服务器连接是否处于活动状态，因此我不得不恢复为从表中包装一个简单的 select 1异常处理程序，只是为了在继续之前戳出连接。

另一种选择是在一个单独的线程中放置一个简单的“保持活动”例程，该例程定期执行一个简单的请求，例如 select 1，以保持数据库正常运行。如果该例程检测到连接已断开，则它将负责将“db_connection_up”标志设置为false或重新连接。

您必须根据要处理的请求数量确定处理它的最佳方法。连接、发出一个微小的请求，然后反复断开连接，是一种不同的坏事，所以你必须找到一个折衷的办法。

与您的 DBA 联系，了解 Oracle DB 中的超时是多少，以及是否可以更改它或者是否可以获得永久连接。如果没有，请调整您的代码。

在 google 上搜索“oracle 侦听器超时”以获取更多信息。

Answer 4

开尔文的答案对我有用。此外，还有另一种方法。

我使用的是 Rails 4.1.x，Gemfile：

gem 'activerecord-oracle_enhanced-adapter', '~> 1.5.0'
gem 'ruby-oci8', '2.2.3'

database.yml：

# not work!
host:  218.5.173.xxx/my_db

# works, solution 1:  
database: 218.5.173.xxx/my_db


# works, solution 2: 
database: "(DESCRIPTION=
(ADDRESS_LIST=(ADDRESS=(PROTOCOL=tcp)(HOST=218.5.173.xxx)(PORT=1521)))
(CONNECT_DATA=(SERVICE_NAME=my_db))
)"