[ http://issues.apache.org/jira/browse/HADOOP-345?page=all ]
Doug Cutting resolved HADOOP-345.
---------------------------------
Fix Version/s: 0.5.0
Resolution: Fixed
I just committed this. Thanks, Michel.
> JobConf access to name-values
> -----------------------------
>
> Key: HADOOP-345
> URL: http://issues.apache.org/jira/browse/HADOOP-345
> Project: Hadoop
> Issue Type: Improvement
> Reporter: Michel Tourn
> Assigned To: Michel Tourn
> Fix For: 0.5.0
>
> Attachments: config.entries.patch
>
>
> class JobConf (or its base class Configuration)
> should be extended to enable enumeration of all its key-value pairs.
> ( more precisely: the Properties returned by Configuration.getProps() )
> This will be useful to "export" all JobConf properties to environment
> variables.
> We use env.vars to expose some Hadoop context to non-Java MapReduce
> applications.
> Note that the typed properties are also represented as Strings
> (getInt, getStrings, getClass, etc.)
> So a single enumeration exposes everything as (untyped) environment variables.
> The proposed escaping rules from JobConf properties to env.var are:
> 1. values are left as-is.
> 2. keys are escaped as follows:
> [A-Za-z0-9] --> unchanged.
> all other chars --> underscore.
> For example
> set("mapred.input.key.class", "com.example.MyKey")
> becomes env.var:
> export mapred_input_key_class=com.example.MyKey
> Justification:
> 1. Environment variables are case-sensitive. (Although uppercase is the
> preferred convention)
> So no need to uppercase everything.
> 2. Some characters are forbidden in env.vars, or at least not shell-friendly:
> For example period, colon are problematic.
> 3. The Hadoop conventions are already hierarchical and provide some namespace
> protection.
> This means we don't need an additional prefix as protection.
> For example all exported environment variables will start with "mapred." ,
> "dfs." , "ipc." etc.
> This means they will not conflict with standard environemnt variables like
> PATH, USER, etc.
> And they will not conflict with standard hadoop env.vars because those are
> upper-case. (like HADOOP_CONF_DIR)
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