public FixedBackoffBuilder delayMillis(long delayMillis) {
        checkArgument(delayMillis >= 0, "delayMillis: %s (expected: >= 0)", delayMillis);
        this.delayMillis = delayMillis;
        return this;
    }
Sets the delay duration in milliseconds for the Fixed {@link Backoff}.

<p>This value determines the fixed amount of time the backoff will delay
before retrying an operation.</p>

@param delayMillis the delay in milliseconds
core/src/main/java/com/linecorp/armeria/client/retry/FixedBackoffBuilder.java