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// Copyright (c) 2023 VMware, Inc. or its affiliates. All rights reserved.
//
// This software, the RabbitMQ Stream Java client library, is dual-licensed under the
// Mozilla Public License 2.0 ("MPL"), and the Apache License version 2 ("ASL").
// For the MPL, please see LICENSE-MPL-RabbitMQ. For the ASL,
// please see LICENSE-APACHE2.
//
// This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND,
// either express or implied. See the LICENSE file for specific language governing
// rights and limitations of this software.
//
// If you have any questions regarding licensing, please contact us at
// [email protected].
package com.rabbitmq.stream;
/**
* API to instrument operations in the stream client. The supported operations are publishing, and
* asynchronous delivery.
*
* Implementations can gather information and send it to tracing backends. This allows e.g.
* following the processing steps of a given message through different systems.
*
*
This is considered an SPI and is susceptible to change at any time.
*
* @since 0.12.0
* @see EnvironmentBuilder#observationCollector(ObservationCollector)
* @see com.rabbitmq.stream.observation.micrometer.MicrometerObservationCollectorBuilder
*/
public interface ObservationCollector {
ObservationCollector NO_OP =
new ObservationCollector() {
@Override
public Void prePublish(String stream, Message message) {
return null;
}
@Override
public void published(Void context, Message message) {}
@Override
public MessageHandler subscribe(MessageHandler handler) {
return handler;
}
};
/**
* Start observation.
*
* Implementations are expecting to return an observation context that will be passed in to the
* {@link #published(Object, Message)} callback.
*
* @param stream the stream to publish to
* @param message the message to publish
* @return observation context
*/
T prePublish(String stream, Message message);
/**
* Callback when the message is about to be published.
*
* @param context the observation context
* @param message the message to publish
*/
void published(T context, Message message);
/**
* Decorate consumer registration.
*
* @param handler the original handler
* @return a decorated handler
*/
MessageHandler subscribe(MessageHandler handler);
/**
* Says whether the implementation does nothing or not.
*
* @return true if the implementation is a no-op
*/
default boolean isNoop() {
return this == NO_OP;
}
}