org.apache.samza.context

Interface TaskContext

public interface TaskContext

The framework-provided context for the current task.

Use ApplicationTaskContext for the application-defined context for the current task.

Method Summary

Modifier and Type	Method and Description
CallbackScheduler	getCallbackScheduler() Gets the CallbackScheduler for this task, which can be used to schedule a callback to be executed at a future time.
KeyValueStore<?,?>	getStore(java.lang.String storeName) Gets the KeyValueStore associated with storeName for this task.
<K,V> ReadWriteTable<K,V>	getTable(java.lang.String tableId) Gets the ReadWriteTable corresponding to the tableId for this task.
MetricsRegistry	getTaskMetricsRegistry() Gets the MetricsRegistry for this task, which can be used to register metrics that are reported per task.
TaskModel	getTaskModel() Gets the TaskModel for this task, which contains this task's name and its SystemStreamPartitions.
<K,V,U> ReadWriteUpdateTable<K,V,U>	getUpdatableTable(java.lang.String tableId) Gets the ReadWriteUpdateTable corresponding to the tableId for this task.
void	setStartingOffset(SystemStreamPartition systemStreamPartition, java.lang.String offset) Sets the starting offset for the given SystemStreamPartition.

Method Detail

getTaskModel

TaskModel getTaskModel()

Gets the TaskModel for this task, which contains this task's name and its SystemStreamPartitions.

Returns:

the TaskModel for this task

getTaskMetricsRegistry

MetricsRegistry getTaskMetricsRegistry()

Gets the MetricsRegistry for this task, which can be used to register metrics that are reported per task.

Returns:

the MetricsRegistry for this task

getStore

KeyValueStore<?,?> getStore(java.lang.String storeName)

Gets the KeyValueStore associated with storeName for this task.

The returned store should be cast with the concrete type parameters based on the configured store serdes. E.g., if using string key and integer value serde, it should be cast to a KeyValueStore<String, Integer>.

Parameters:

storeName - name of the KeyValueStore to get for this task

Returns:

the KeyValueStore associated with storeName for this task

Throws:

java.lang.IllegalArgumentException - if there is no store associated with storeName

getUpdatableTable

<K,V,U> ReadWriteUpdateTable<K,V,U> getUpdatableTable(java.lang.String tableId)

Gets the ReadWriteUpdateTable corresponding to the tableId for this task.

Type Parameters:

K - the type of the key in this table

V - the type of the value in this table

U - the type of the update applied to records in this table

Parameters:

tableId - id of the ReadWriteUpdateTable to get

Returns:

the ReadWriteUpdateTable associated with tableId for this task

Throws:

java.lang.IllegalArgumentException - if there is no table associated with tableId

getTable

<K,V> ReadWriteTable<K,V> getTable(java.lang.String tableId)

Gets the ReadWriteTable corresponding to the tableId for this task. This is retained for backward compatibility of the API. Please prefer the use of getUpdatableTable(String) instead as it provides the ability to do updates as well.

Type Parameters:

K - the type of the key in this table

V - the type of the value in this table

Parameters:

tableId - id of the ReadWriteTable to get

Returns:

the ReadWriteTable associated with tableId for this task

Throws:

java.lang.IllegalArgumentException - if there is no table associated with tableId

getCallbackScheduler

CallbackScheduler getCallbackScheduler()

Gets the CallbackScheduler for this task, which can be used to schedule a callback to be executed at a future time.

Returns:

the CallbackScheduler for this task

setStartingOffset

@InterfaceStability.Evolving
void setStartingOffset(SystemStreamPartition systemStreamPartition,
                                                    java.lang.String offset)

Sets the starting offset for the given SystemStreamPartition.

Offsets can only be set for a SystemStreamPartition assigned to this task. The SystemStreamPartitions assigned to this task can be accessed through TaskModel.getSystemStreamPartitions() for the TaskModel obtained by calling getTaskModel(). Trying to set the offset for any other partition will have no effect. NOTE: this feature is experimental, and the API may change in a future release.

Parameters:

systemStreamPartition - SystemStreamPartition whose offset should be set

offset - to set for the given SystemStreamPartition