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 support both of them.
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"> someproperty=somevalue hive.exec.scratchdir=/tmp/mydir </hdp:hive-server>
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.
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. Furthermore, the client
definition also allows Hive scripts (either declared inlined or
externally) to be executed during initialization, once the client
connects; this is quite useful for doing Hive specific initialization:
<hive-client-factory host="some-host" port="some-port" xmlns="http://www.springframework.org/schema/hadoop"> <hdp:script> DROP TABLE IF EXITS testHiveBatchTable; CREATE TABLE testHiveBatchTable (key int, value string); </hdp:script> <hdp:script location="classpath:org/company/hive/script.q"> <arguments>ignore-case=true</arguments> </hdp:script> </hive-client-factory>
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 consider using a tasklet) by the factory. The first script is defined inline while the second is read from the classpath and passed one parameter. For more information on using parameters (or variables) in Hive scripts, see Hive manual.
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.
Warning | |
---|---|
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" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:c="http://www.springframework.org/schema/c" xmlns:context="http://www.springframework.org/schema/context" 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 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"/> </beans>
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.
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"> <hdp:script> DROP TABLE IF EXITS testHiveBatchTable; CREATE TABLE testHiveBatchTable (key int, value string); </hdp:script> <hdp:script location="hive-scripts/script.q"/> </hdp:hive-runner>
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.
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 straightforward:
<hdp:hive-tasklet id="hive-script"> <hdp:script> DROP TABLE IF EXITS testHiveBatchTable; CREATE TABLE testHiveBatchTable (key int, value string); </hdp:script> <hdp:script location="classpath:org/company/hive/script.q" /> </hdp:hive-tasklet>
The tasklet above executes two scripts - one declared as part of the bean definition followed by another located on the classpath.
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>>() { @Override 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 have 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 `DataAccessException`s. Thus the
application only has to track only one exception hierarchy across all
data technologies instead of one per technology.