org.apache.samza.operators

Interface StreamGraph

@InterfaceStability.Unstable
public interface StreamGraph

Provides access to MessageStreams and OutputStreams used to describe application logic.

Method Summary

Modifier and Type	Method and Description
<M> MessageStream<M>	getInputStream(java.lang.String streamId) Same as getInputStream(String, Serde), but uses the default Serde provided via setDefaultSerde(Serde) for deserializing input messages.
<M> MessageStream<M>	getInputStream(java.lang.String streamId, Serde<M> serde) Gets the input MessageStream corresponding to the streamId.
<M> OutputStream<M>	getOutputStream(java.lang.String streamId) Same as getOutputStream(String, Serde), but uses the default Serde provided via setDefaultSerde(Serde) for serializing output messages.
<M> OutputStream<M>	getOutputStream(java.lang.String streamId, Serde<M> serde) Gets the OutputStream corresponding to the streamId.
void	setDefaultSerde(Serde<?> serde) Sets the default Serde to use for (de)serializing messages.
StreamGraph	withContextManager(ContextManager contextManager) Sets the ContextManager for this StreamGraph.

Method Detail

setDefaultSerde

void setDefaultSerde(Serde<?> serde)

Sets the default Serde to use for (de)serializing messages.

. If the default serde is set, it must be set before creating any input or output streams.

If no explicit or default serdes are provided, a KVSerde<NoOpSerde, NoOpSerde> is used. This means that any streams created without explicit or default serdes should be cast to MessageStream<KV<Object, Object>>.

Providing an incompatible message type for the input/output streams that use the default serde will result in ClassCastExceptions at runtime.

Parameters:

serde - the default message Serde to use

getInputStream

<M> MessageStream<M> getInputStream(java.lang.String streamId,
                                    Serde<M> serde)

Gets the input MessageStream corresponding to the streamId.

An input MessageStream<KV<K, V>, which can be obtained by calling this method with a KVSerde<K, V>, can receive messages of type KV<K, V>. An input MessageStream<M> with any other Serde<M> can receive messages of type M - the key in the incoming message is ignored.

A KVSerde<NoOpSerde, NoOpSerde> or NoOpSerde may be used if the SystemConsumer deserializes the incoming messages itself, and no further deserialization is required from the framework.

Multiple invocations of this method with the same streamId will throw an IllegalStateException.

Type Parameters:

M - the type of messages in the input MessageStream

Parameters:

streamId - the unique ID for the stream

serde - the Serde to use for deserializing incoming messages

Returns:

the input MessageStream

Throws:

java.lang.IllegalStateException - when invoked multiple times with the same streamId

getInputStream

<M> MessageStream<M> getInputStream(java.lang.String streamId)

Same as getInputStream(String, Serde), but uses the default Serde provided via setDefaultSerde(Serde) for deserializing input messages.

If no default serde has been provided before calling this method, a KVSerde<NoOpSerde, NoOpSerde> is used. Providing a message type M that is incompatible with the default Serde will result in ClassCastExceptions at runtime.

Multiple invocations of this method with the same streamId will throw an IllegalStateException.

Type Parameters:

M - the type of message in the input MessageStream

Parameters:

streamId - the unique ID for the stream

Returns:

the input MessageStream

Throws:

java.lang.IllegalStateException - when invoked multiple times with the same streamId

getOutputStream

<M> OutputStream<M> getOutputStream(java.lang.String streamId,
                                    Serde<M> serde)

Gets the OutputStream corresponding to the streamId.

An OutputStream<KV<K, V>>, which can be obtained by calling this method with a KVSerde<K, V>, can send messages of type KV<K, V>. An OutputStream<M> with any other Serde<M> can send messages of type M without a key.

A KVSerde<NoOpSerde, NoOpSerde> or NoOpSerde may be used if the SystemProducer serializes the outgoing messages itself, and no prior serialization is required from the framework.

When sending messages to an OutputStream<KV<K, V>>, messages are partitioned using their serialized key. When sending messages to any other OutputStream<M>, messages are partitioned using a null partition key.

Multiple invocations of this method with the same streamId will throw an IllegalStateException.

Type Parameters:

M - the type of messages in the OutputStream

Parameters:

streamId - the unique ID for the stream

serde - the Serde to use for serializing outgoing messages

Returns:

the output MessageStream

Throws:

java.lang.IllegalStateException - when invoked multiple times with the same streamId

getOutputStream

<M> OutputStream<M> getOutputStream(java.lang.String streamId)

Same as getOutputStream(String, Serde), but uses the default Serde provided via setDefaultSerde(Serde) for serializing output messages.

If no default serde has been provided before calling this method, a KVSerde<NoOpSerde, NoOpSerde> is used. Providing a message type M that is incompatible with the default Serde will result in ClassCastExceptions at runtime.

Multiple invocations of this method with the same streamId will throw an IllegalStateException.

Type Parameters:

M - the type of messages in the OutputStream

Parameters:

streamId - the unique ID for the stream

Returns:

the output MessageStream

Throws:

java.lang.IllegalStateException - when invoked multiple times with the same streamId

withContextManager

StreamGraph withContextManager(ContextManager contextManager)

Sets the ContextManager for this StreamGraph.

The provided ContextManager can be used to setup shared context between the operator functions within a task instance

Parameters:

contextManager - the ContextManager to use for the StreamGraph

Returns:

the StreamGraph with contextManager set as its ContextManager