org.apache.lens.server.api.driver

Interface LensDriver

All Superinterfaces:

Externalizable, Serializable

All Known Implementing Classes:

AbstractLensDriver, ESDriver, HiveDriver, JDBCDriver

public interface LensDriver
extends Externalizable

The Interface LensDriver.

Method Summary

Modifier and Type	Method and Description
boolean	cancelQuery(QueryHandle handle) Cancel the execution of the query, specified by the handle.
void	close() Close the driver, releasing all resouces used up by the driver.
void	closePreparedQuery(QueryPrepareHandle handle) Close the prepare query specified by the prepared handle, releases all the resources held by the prepared query.
void	closeQuery(QueryHandle handle) Close the query specified by the handle, releases all the resources held by the query.
void	closeResultSet(QueryHandle handle) Close the resultset for the query.
void	configure(org.apache.hadoop.conf.Configuration conf, String driverType, String driverName) Configure driver with Configuration passed.
Priority	decidePriority(AbstractQueryContext queryContext) decide priority based on query's cost.
QueryCost	estimate(AbstractQueryContext qctx) Estimate the cost of execution for given query.
LensResultSet	execute(QueryContext context) Blocking execute of the query
void	executeAsync(QueryContext context) Asynchronously execute the query.
DriverQueryPlan	explain(AbstractQueryContext explainCtx) Explain the given query.
DriverQueryPlan	explainAndPrepare(PreparedQueryContext pContext) Explain and prepare the given query.
LensResultSet	fetchResultSet(QueryContext context) Fetch the results of the query, specified by the handle.
org.apache.hadoop.conf.Configuration	getConf() Get driver configuration
String	getFullyQualifiedName()
com.google.common.collect.ImmutableSet<QueryLaunchingConstraint>	getQueryConstraints()
DriverQueryHook	getQueryHook()
RetryPolicyDecider<QueryContext>	getRetryPolicyDecider()
StatusUpdateMethod	getStatusUpdateMethod()
com.google.common.collect.ImmutableSet<WaitingQueriesSelectionPolicy>	getWaitingQuerySelectionPolicies()
void	prepare(PreparedQueryContext pContext) Prepare the given query.
void	registerDriverEventListener(LensEventListener<DriverEvent> driverEventListener) Add a listener for driver events.
void	registerForCompletionNotification(QueryContext context, long timeoutMillis, QueryCompletionListener listener) Register for query completion notification.
void	updateStatus(QueryContext context) Update driver query status in the context object.

Methods inherited from interface java.io.Externalizable

readExternal, writeExternal

Method Detail

getConf

org.apache.hadoop.conf.Configuration getConf()

Get driver configuration

configure

void configure(org.apache.hadoop.conf.Configuration conf,
               String driverType,
               String driverName)
        throws LensException

Configure driver with Configuration passed.

Parameters:

conf - The configuration object

driverType - Type of the driver (Example: hive, jdbc, el)

driverName - Name of this driver

Throws:

LensException - the lens exception

estimate

QueryCost estimate(AbstractQueryContext qctx)
            throws LensException

Estimate the cost of execution for given query. This should be returned with very less latency - should return within 10s of milli seconds.

Parameters:

qctx - The query context

Returns:

The QueryCostTO object

Throws:

LensException - the lens exception if driver cannot estimate

explain

DriverQueryPlan explain(AbstractQueryContext explainCtx)
                 throws LensException

Explain the given query.

Parameters:

explainCtx - The explain context

Returns:

The query plan object

Throws:

LensException - the lens exception

prepare

void prepare(PreparedQueryContext pContext)
      throws LensException

Prepare the given query.

Parameters:

pContext - the context

Throws:

LensException - the lens exception

explainAndPrepare

DriverQueryPlan explainAndPrepare(PreparedQueryContext pContext)
                           throws LensException

Explain and prepare the given query.

Parameters:

pContext - the context

Returns:

The query plan object;

Throws:

LensException - the lens exception

closePreparedQuery

void closePreparedQuery(QueryPrepareHandle handle)
                 throws LensException

Close the prepare query specified by the prepared handle, releases all the resources held by the prepared query.

Parameters:

handle - The query handle

Throws:

LensException - the lens exception

execute

LensResultSet execute(QueryContext context)
               throws LensException

Blocking execute of the query

The driver would be closing the driver handle, once the results are fetched.

Parameters:

context - the context

Returns:

returns the result set, null if there is no result available

Throws:

LensException - the lens exception

executeAsync

void executeAsync(QueryContext context)
           throws LensException

Asynchronously execute the query.

Parameters:

context - The query context

Throws:

LensException - the lens exception

registerForCompletionNotification

void registerForCompletionNotification(QueryContext context,
                                       long timeoutMillis,
                                       QueryCompletionListener listener)
                                throws LensException

Register for query completion notification.

Parameters:

context - the context

timeoutMillis - the timeout millis

listener - the listener. Only query completions are guaranteed to be notified. Notably: SUCCESS and FAILURE

Throws:

LensException - the lens exception

updateStatus

void updateStatus(QueryContext context)
           throws LensException

Update driver query status in the context object.

Parameters:

context - The query context

Throws:

LensException - the lens exception

fetchResultSet

LensResultSet fetchResultSet(QueryContext context)
                      throws LensException

Fetch the results of the query, specified by the handle.

Parameters:

context - The query context

Returns:

returns the result set

Throws:

LensException - the lens exception

closeResultSet

void closeResultSet(QueryHandle handle)
             throws LensException

Close the resultset for the query. Closing an already closed resultset should not result in failures.

Parameters:

handle - The query handle

Throws:

LensException - the lens exception

cancelQuery

boolean cancelQuery(QueryHandle handle)
             throws LensException

Cancel the execution of the query, specified by the handle.

Parameters:

handle - The query handle.

Returns:

true if cancel was successful, false otherwise

Throws:

LensException - the lens exception

closeQuery

void closeQuery(QueryHandle handle)
         throws LensException

Close the query specified by the handle, releases all the resources held by the query.

Parameters:

handle - The query handle

Throws:

LensException - the lens exception

close

void close()
    throws LensException

Close the driver, releasing all resouces used up by the driver.

Throws:

LensException - the lens exception

registerDriverEventListener

void registerDriverEventListener(LensEventListener<DriverEvent> driverEventListener)

Add a listener for driver events.

Parameters:

driverEventListener - the driver event listener

getQueryConstraints

com.google.common.collect.ImmutableSet<QueryLaunchingConstraint> getQueryConstraints()

Returns:

The QueryLaunchingConstraints to be checked before launching a query on driver. If there are no driver level constraints, then an empty set is returned. null is never returned.

getWaitingQuerySelectionPolicies

com.google.common.collect.ImmutableSet<WaitingQueriesSelectionPolicy> getWaitingQuerySelectionPolicies()

Returns:

The WaitingQueriesSelectionPolicys to be used to select waiting queries eligible to be moved out of waiting state. If there are no driver level waiting query selection policies, then an empty set is returned. null is never returned.

getFullyQualifiedName

String getFullyQualifiedName()

Returns:

fully qualified name of this driver. This should be unique for each driver instance. This name can be used for referring to the driver while logging, persisting and restoring driver details,etc. (Examples: hive/hive1, jdbc/mysql1 )

decidePriority

Priority decidePriority(AbstractQueryContext queryContext)

decide priority based on query's cost. The cost should be already computed by estimate call, but it's not guaranteed to be pre-computed. It's up to the driver to do an on-demand computation of cost.

Parameters:

queryContext - Query context whose priority is to be decided

getQueryHook

DriverQueryHook getQueryHook()

Returns:

the DriverQueryHook implementation for the driver.

See Also:

for more details.

getStatusUpdateMethod

StatusUpdateMethod getStatusUpdateMethod()

Returns:

The method of status update supported by this driver.

getRetryPolicyDecider

RetryPolicyDecider<QueryContext> getRetryPolicyDecider()