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https://issues.apache.org/jira/browse/HADOOP-7001?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Patrick Kling updated HADOOP-7001:
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Attachment: HADOOP-7001.2.patch
As suggested by Doug, I have renamed the methods in Reconfigurable. I have also
renamed ConfigurationChangeException to ReconfigurationException and
ConfigurationChangeServlet to ReconfigurationServlet to keep everything
consistent.
Please see HDFS-1477 for a patch that makes NameNode Reconfigurable and allows
us to change 2 properties.
The servlet now returns error code 500 if a change fails.
A command line tool for changing configuration properties sounds like a good
idea but I am not quite sure how to provide a generic version of such a tool.
If the command line tool runs locally, very little functionality beyond calling
the interface methods would be needed. Maybe it would be best to leave command
line utilities to a later JIRA once it becomes more clear if there is a need
for additional support.
> Allow configuration changes without restarting configured nodes
> ---------------------------------------------------------------
>
> Key: HADOOP-7001
> URL: https://issues.apache.org/jira/browse/HADOOP-7001
> Project: Hadoop Common
> Issue Type: Task
> Reporter: Patrick Kling
> Assignee: Patrick Kling
> Attachments: HADOOP-7001.2.patch, HADOOP-7001.patch,
> reconfigurable.patch
>
>
> Currently, changing the configuration on a node (e.g., the name node)
> requires that we restart the node. We propose a change that would allow us to
> make configuration changes without restarting. Nodes that support
> configuration changes at run time should implement the following interface:
> interface ChangeableConfigured extends Configured {
> void changeConfiguration(Configuration newConf) throws
> ConfigurationChangeException;
> }
> The contract of changeConfiguration is as follows:
> The node will compare newConf to the existing configuration. For each
> configuration property that is set to a different value than in the current
> configuration, the node will either adjust its behaviour to conform to the
> new configuration or throw a ConfigurationChangeException if this change is
> not possible at run time. If a configuration property is set in the current
> configuration but is unset in newConf, the node should use its default value
> for this property. After a successful invocation of changeConfiguration, the
> behaviour of the configured node should be indistinguishable from the
> behaviour of a node that was configured with newConf at creation.
> It should be easy to change existing nodes to implement this interface. We
> can start by throwing the exception for all changes and then gradually start
> supporting more and more changes at run time. (We might even consider
> replacing Configured with ChangeableConfigured entirely, but I think the
> proposal above afford greater flexibility).
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