com.pushtechnology.diffusion.client.features

Interface UpdateStream<T>

Type Parameters:

T - type of the value

public interface UpdateStream<T>

An update stream provides a method for updating a specific topic.

An update stream is associated with a specific topic. Update streams are created using TopicUpdate.newUpdateStreamBuilder(). It can be created with an optional constraint. An optional TopicSpecification can be provided on creation. The type of the topic must match the type of values passed to the update stream. The existence of the topic, its type and the constraint are validated lazily by the first set(T) or validate() operation. Subsequent operations issued before the first operation completes will be deferred until the completion of the first operation.

An update stream can be used to send any number of updates. It sends a sequence of updates for a specific topic to the server. If supported by the data type, updates will be sent to the server as a stream of binary deltas. An update stream does not prevent other sessions from updating the topic. If exclusive access is required update streams should be used with session locks as constraints.

Once validated an update stream can be invalidated. An invalidated update stream rejects the operations applied to it. The update stream will be invalidated if:

• the topic is removed
• another update stream is created for the same topic
• the topic is updated to a new value by anything other than the stream
• the session does not have the UPDATE_TOPIC permission
• an operation fails because of cluster repartitioning

Update streams are thread-safe.

Since:

6.2

Author:

DiffusionData Limited

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static interface	UpdateStream.Builder Builder for update stream to use for updating a specific topic.

Method Summary

Modifier and Type	Method and Description
T	get() Return the latest value of the topic set using this update stream.
CompletableFuture<TopicCreationResult>	set(T value) Sets the topic to a specified value.
CompletableFuture<TopicCreationResult>	validate() Validates the update stream.

Method Detail

set

CompletableFuture<TopicCreationResult> set(T value)

Sets the topic to a specified value.

The null value can only be passed to the value parameter when updating string, int64, or double topics.

When a string, int64, or double topic is set to null, the topic will be updated to have no value. If a previous value was present subscribers will receive a notification that the new value is null. New subscribers will not receive a value notification.

The first call to this method may fail with NoSuchTopicException or IncompatibleTopicException. Subsequent calls may fail with InvalidUpdateStreamException. Any call can fail with ClusterRoutingException, PermissionsException or SessionClosedException.

If a constraint was provided when creating the update stream, the first call to this method may also fail with UnsatisfiedConstraintException.

If the update stream was created with a TopicSpecification, the first call to this method may also fail with TopicControl.IncompatibleExistingTopicException and it will not fail with NoSuchTopicException.

If this method fails all subsequent calls to set(T) or validate() will fail with InvalidUpdateStreamException.

Parameters:

value - the value. Update streams for string, int64, and double topics accept null, as described above. Using null with other topic types is an error and will result in a NullPointerException.

Returns:

a CompletableFuture that completes when a response is received from the server.

If the task fails, the CompletableFuture will complete exceptionally with a CompletionException. Common reasons for failure, listed by the exception reported as the cause, include:

• NoSuchTopicException – if there is no topic bound to path;
• IncompatibleTopicException – if updates cannot be applied to the topic, for example if a topic view has bound a reference topic to the path;
• IncompatibleTopicStateException – if the topic is managed by a component (such as fan-out) that prohibits updates from the caller;
• UnsatisfiedConstraintException – if the constraint is not satisfied by the topic path;
• InvalidUpdateStreamException – the update stream has been invalidated;
• TopicControl.IncompatibleParentTopicException – a topic could not be added because a topic at a parent path is incompatible;
• TopicControl.InvalidTopicPathException – topicPath is not a valid topic path;
• TopicControl.InvalidTopicSpecificationException – the specification is invalid, possibly because mandatory properties not supplied;
• TopicControl.TopicLicenseLimitException – the topic could not be added as it would breach a licensing limit;
• ClusterRoutingException – if the operation failed due to a transient cluster error;
• PermissionsException – if the calling session does not have the MODIFY_TOPIC or UPDATE_TOPIC permission for path;
• SessionClosedException – if the session is closed.

get

T get()

Return the latest value of the topic set using this update stream.

The returned value reflects the last value that has been set, before it is sent to the server.

If the server rejects a set operation, the topic value will not change and this update stream will be invalidated.

Returns:

the cached value of the topic

Throws:

IllegalStateException - if called before the first call to set(T)

validate

CompletableFuture<TopicCreationResult> validate()

Validates the update stream.

Update streams are validated lazily when setting the value. This method allows the stream to be validated before a value needs to be set.

If the update stream has not been validated yet, calling this method checks the topic exists, the topic type is correct, the constraint is satisfied and the session has permission to update the topic. Once it has been validated calling this method checks the topic has not been removed, no other stream has been created for the topic, the value of the topic has not been changed by anything else and the session still has permission to update the topic.

This method may fail with TopicControl.IncompatibleExistingTopicException if it is the first call to validate(), set(T) has not been called and a topic specification was provided when creating the update stream, otherwise it will never fail with this cause.

The first call to this method may fail with NoSuchTopicException or IncompatibleTopicException. Subsequent calls may fail with InvalidUpdateStreamException. Any call can fail with ClusterRoutingException, PermissionsException or SessionClosedException.

If a constraint was provided when creating the update stream, the first call to this method may also fail with UnsatisfiedConstraintException.

If the update stream was created with a TopicSpecification, the first call to this method may also fail with TopicControl.IncompatibleExistingTopicException and it will not fail with NoSuchTopicException.

If this method fails all subsequent calls to set(T) or validate() will fail with InvalidUpdateStreamException.

Returns:

a CompletableFuture that completes when a response is received from the server.

If the task fails, the CompletableFuture will complete exceptionally with a CompletionException. Common reasons for failure, listed by the exception reported as the cause, include:

• NoSuchTopicException – if there is no topic bound to path;
• IncompatibleTopicException – if updates cannot be applied to the topic, for example if a topic view has bound a reference topic to the path;
• IncompatibleTopicStateException – if the topic is managed by a component (such as fan-out) that prohibits updates from the caller;
• UnsatisfiedConstraintException – if the constraint is not satisfied by the topic path;
• InvalidUpdateStreamException – the update stream has been invalidated;
• ClusterRoutingException – if the operation failed due to a transient cluster error;
• PermissionsException – if the calling session does not have the MODIFY_TOPIC or UPDATE_TOPIC permission for path;
• SessionClosedException – if the session is closed.