BackoffStrategy.java

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 * to you under the Apache License, Version 2.0 (the
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 *
 *   http://www.apache.org/licenses/LICENSE-2.0
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 * KIND, either express or implied.  See the License for the
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 *
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package org.apache.hc.client5.http.sse;

/**
 * Computes the next reconnect delay for SSE (in milliseconds).
 * <p>
 * Implementations may also override {@link #shouldReconnect(int, long, Long)}
 * to decline reconnects entirely (e.g., a "no strategy" that never reconnects).
 */
public interface BackoffStrategy {

    /**
     * @param attempt           consecutive reconnect attempt number (1-based)
     * @param previousDelayMs   last delay used (0 for first attempt)
     * @param serverRetryHintMs value from server 'retry:' (ms) or HTTP Retry-After, or null if none
     * @return delay in milliseconds, greater than or equal to {@code 0}
     */
    long nextDelayMs(int attempt, long previousDelayMs, Long serverRetryHintMs);

    /**
     * Whether a reconnect should be attempted at all.
     * Default is {@code true} for backward compatibility.
     *
     * @param attempt           consecutive reconnect attempt number (1-based)
     * @param previousDelayMs   last delay used (0 for first attempt)
     * @param serverRetryHintMs value from server 'retry:' (ms) or HTTP Retry-After, or null if none
     * @return {@code true} to reconnect, {@code false} to stop
     */
    default boolean shouldReconnect(final int attempt, final long previousDelayMs, final Long serverRetryHintMs) {
        return true;
    }
}