Quick Tip on Using Sqoop Action in Oozie

Another Oozie tip blog post.

If you try to use Sqoop action in Oozie, you know you can use the “command” format, with the entire Sqoop configuration in a single line:

<pre><workflow-app name="sample-wf" xmlns="uri:oozie:workflow:0.1">
    ...
    <action name="myfirsthivejob">
        <sqoop xmlns="uri:oozie:sqoop-action:0.2">
            <job-traker>foo:8021</job-tracker>
            <name-node>bar:8020</name-node>
            <command>import  --connect jdbc:hsqldb:file:db.hsqldb --table TT --target-dir hdfs://localhost:8020/user/tucu/foo -m 1</command>
        </sqoop>
        <ok to="myotherjob"/>
        <error to="errorcleanup"/>
    </action>
    ...
</workflow-app>

This is convenient, but can be difficult to read and maintain. I prefer using the “arg” syntax, with each argument in its own line:

<workflow-app name="sample-wf" xmlns="uri:oozie:workflow:0.1">
    ...
    <action name="myfirsthivejob">
        <sqoop xmlns="uri:oozie:sqoop-action:0.2">
            <job-traker>foo:8021</job-tracker>
            <name-node>bar:8020</name-node>
            <arg>import</arg>
            <arg>--connect</arg>
            <arg>jdbc:hsqldb:file:db.hsqldb</arg>
            <arg>--table</arg>
            <arg>TT</arg>
            <arg>--target-dir</arg>
            <arg>hdfs://localhost:8020/user/tucu/foo</arg>
            <arg>-m</arg>
            <arg>1</arg>
        </sqoop>
        <ok to="myotherjob"/>
        <error to="errorcleanup"/>
    </action>
    ...
</workflow-app>

As you can see, each argument here is in its own “arg” tag. Even two arguments that belong together like “–table” and “TT” go in two separate tags.
If you’ll try to put them together for readability, as I did, Sqoop will throw its entire user manual at you. It took me a while to figure out why this is an issue.

When you call Oozie from the command line, all the arguments you pass are sent as a String[] array, and the spaces separate the arguments into array elements. So if you call Sqoop with “–table TT” it will be two elements, “–table” and “TT”.
When using “arg” tags in Oozie, you are basically generating the same array in XML. Oozie will turn the XML argument list into an array and pass it to Sqoop just the way it would in the command line. Then Sqoop parses it in exactly the same way.
So every item separated with space in the command line must be in separate tags in Oozie.

Its simple and logical once you figure out why :)
If you want to dig a bit more into how Sqoop parses its arguments, it is using Apache Commons CLI with GnuParser. You can read all about it.

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