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There is a newer version: 1.4.0

/**
 * Copyright 2022 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package io.micrometer.tracing.http;

import io.micrometer.tracing.http.HttpClientRequest;
import io.micrometer.tracing.http.HttpClientResponse;
import io.micrometer.tracing.Span;
import io.micrometer.tracing.TraceContext;
import io.micrometer.common.lang.Nullable;

/**
 * This API is taken from OpenZipkin Brave.
 * 
 * This standardizes a way to instrument http clients, particularly in a way that
 * encourages use of portable customizations via {@link HttpRequestParser} and
 * {@link HttpResponseParser}.
 *
 * @author OpenZipkin Brave Authors
 * @author Marcin Grzejszczak
 * @since 1.0.0
 */
public interface HttpClientHandler {

    /**
     * Starts the client span after assigning it a name and tags. This injects the trace
     * context onto the request before returning.
     * 
     * Call this before sending the request on the wire.
     * @param request to inject the tracing context with
     * @return client side span
     */
    Span handleSend(HttpClientRequest request);

    /**
     * Same as {@link #handleSend(HttpClientRequest)} but with an explicit parent
     * {@link TraceContext}.
     * @param request to inject the tracing context with
     * @param parent {@link TraceContext} that is to be the client side span's parent
     * @return client side span
     */
    Span handleSend(HttpClientRequest request, @Nullable TraceContext parent);

    /**
     * Finishes the client span after assigning it tags according to the response or
     * error.
     * @param response the HTTP response
     * @param span span to be ended
     */
    void handleReceive(HttpClientResponse response, Span span);

}