5. Hive integration

When working with http://hive.apache.org from a Java environment, one can choose between the Thrift client or using the Hive JDBC-like driver. Both have their pros and cons but no matter the choice, Spring and SHDP supports both of them.

5.1 Starting a Hive Server

SHDP provides a dedicated namespace element for starting a Hive server as a Thrift service (only when using Hive 0.8 or higher). Simply specify the host, the port (the defaults are localhost and 10000 respectively) and you're good to go:

<!-- by default, the definition name is 'hive-server' -->
<hdp:hive-server host="some-other-host" port="10001" />

If needed the Hadoop configuration can be passed in or additional properties specified. In fact hiver-server provides the same properties configuration knobs as hadoop configuration:

<hdp:hive-server host="some-other-host" port="10001" properties-location="classpath:hive-dev.properties" configuration-ref="hadoopConfiguration">

The Hive server is bound to the enclosing application context life-cycle, that is it will automatically startup and shutdown along-side the application context.

5.2 Using the Hive Thrift Client

Similar to the server, SHDP provides a dedicated namespace element for configuring a Hive client (that is Hive accessing a server node through the Thrift). Likewise, simply specify the host, the port (the defaults are localhost and 10000 respectively) and you're done:

<!-- by default, the definition name is 'hiveClientFactory' -->
<hdp:hive-client-factory host="some-other-host" port="10001" />

Note that since Thrift clients are not thread-safe, hive-client-factory returns a factory (named org.springframework.data.hadoop.hive.HiveClientFactory) for creating HiveClient new instances for each invocation. Further more, the client definition also allows Hive scripts (either declared inlined or externally) to be executed during initialization, once the client connects; this quite useful for doing Hive specific initialization:

<hive-client-factory host="some-host" port="some-port" xmlns="http://www.springframework.org/schema/hadoop">
     DROP TABLE IF EXITS testHiveBatchTable; 
     CREATE TABLE testHiveBatchTable (key int, value string);
   <hdp:script location="classpath:org/company/hive/script.q">

In the example above, two scripts are executed each time a new Hive client is created (if the scripts need to be executed only once considering using a tasklet) by the factory. The first executed a script defined inlined while the second read the script from the classpath and passed one parameter to it. For more information on using parameter (or variables) in Hive scripts, see this section in the Hive manual.

5.3 Using the Hive JDBC Client

Another attractive option for accessing Hive is through its JDBC driver. This exposes Hive through the JDBC API meaning one can use the standard API or its derived utilities to interact with Hive, such as the rich JDBC support in Spring Framework.


Note that the JDBC driver is a work-in-progress and not all the JDBC features are available (and probably never will since Hive cannot support all of them as it is not the typical relational database). Do read the official documentation and examples.

SHDP does not offer any dedicated support for the JDBC integration - Spring Framework itself provides the needed tools; simply configure Hive as you would with any other JDBC Driver:

<beans xmlns="http://www.springframework.org/schema/beans"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
      	http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">
    <!-- basic Hive driver bean -->
    <bean id="hive-driver" class="org.apache.hadoop.hive.jdbc.HiveDriver"/>

    <!-- wrapping a basic datasource around the driver -->
    <!-- notice the 'c:' namespace (available in Spring 3.1+) for inlining constructor arguments, 
         in this case the url (default is 'jdbc:hive://localhost:10000/default') -->
    <bean id="hive-ds" class="org.springframework.jdbc.datasource.SimpleDriverDataSource"
       c:driver-ref="hive-driver" c:url="${hive.url}"/>

    <!-- standard JdbcTemplate declaration -->
    <bean id="template" class="org.springframework.jdbc.core.JdbcTemplate" c:data-source-ref="hive-ds"/>
    <context:property-placeholder location="hive.properties"/>

And that is it! Following the example above, one can use the hive-ds DataSource bean to manually get a hold of Connections or better yet, use Spring's JdbcTemplate as in the example above.

5.4 Running a Hive script or query

Like the rest of the Spring Hadoop components, a runner is provided out of the box for executing Hive scripts, either inlined or from various locations through hive-runner element:

<hdp:hive-runner id="hiveRunner" run-at-startup="true">
     DROP TABLE IF EXITS testHiveBatchTable; 
     CREATE TABLE testHiveBatchTable (key int, value string);
   <hdp:script location="hive-scripts/script.q"/>

The runner will trigger the execution during the application start-up (notice the run-at-startup flag which is by default false). Do note that the runner will not run unless triggered manually or if run-at-startup is set to true. Additionally the runner (as in fact do all runners in SHDP) allows one or multiple pre and post actions to be specified to be executed before and after each run. Typically other runners (such as other jobs or scripts) can be specified but any JDK Callable can be passed in. For more information on runners, see the dedicated chapter.

5.4.1 Using the Hive tasklet

For Spring Batch environments, SHDP provides a dedicated tasklet to execute Hive queries, on demand, as part of a batch or workflow. The declaration is pretty straight forward:

<hdp:hive-tasklet id="hive-script">
     DROP TABLE IF EXITS testHiveBatchTable; 
     CREATE TABLE testHiveBatchTable (key int, value string);
   <hdp:script location="classpath:org/company/hive/script.q" />

The tasklet above executes two scripts - one declared as part of the bean definition followed by another located on the classpath.

5.5 Interacting with the Hive API

For those that need to programmatically interact with the Hive API, Spring for Apache Hadoop provides a dedicated template, similar to the aforementioned JdbcTemplate. The template handles the redundant, boiler-plate code, required for interacting with Hive such as, creating a new HiveClient, executing the queries, catching any exceptions and performing clean-up. One can programmatically execute queries (and get the raw results or convert them to longs or ints) or scripts but also interact with the Hive API through the HiveClientCallback. For example:

<hdp:hive-client-factory ... />
<!-- Hive template wires automatically to 'hiveClientFactory'-->
<hdp:hive-template />
<!-- wire hive template into a bean -->
<bean id="someBean" class="org.SomeClass" p:hive-template-ref="hiveTemplate"/>
public class SomeClass {

private HiveTemplate template;

public void setHiveTemplate(HiveTemplate template) { this.template = template; }

public List<String> getDbs() {
    return hiveTemplate.execute(new HiveClientCallback<List<String>>() {
       public List<String> doInHive(HiveClient hiveClient) throws Exception {
          return hiveClient.get_all_databases();

The example above shows a basic container configuration wiring a HiveTemplate into a user class which uses it to interact with the HiveClient Thrift API. Notice that the user does not has to handle the lifecycle of the HiveClient instance or catch any exception (out of the many thrown by Hive itself and the Thrift fabric) - these are handled automatically by the template which converts them, like the rest of the Spring templates, into DataAccessExceptions. Thus the application only has to track only one exception hierarchy across all data technologies instead of one per technology.