public static float updateEstimation(String topic, CompressionType type, float observedRatio) {
        float[] compressionRatioForTopic = getAndCreateEstimationIfAbsent(topic);
        float currentEstimation = compressionRatioForTopic[type.id];
        synchronized (compressionRatioForTopic) {
            if (observedRatio > currentEstimation)
                compressionRatioForTopic[type.id] = Math.max(currentEstimation + COMPRESSION_RATIO_DETERIORATE_STEP, observedRatio);
            else if (observedRatio < currentEstimation) {
                compressionRatioForTopic[type.id] = Math.max(currentEstimation - COMPRESSION_RATIO_IMPROVING_STEP, observedRatio);
            }
        }
        return compressionRatioForTopic[type.id];
    }
@Test
    public void testUpdateEstimation() {
        class EstimationsObservedRatios {
            final float currentEstimation;
            final float observedRatio;
            EstimationsObservedRatios(float currentEstimation, float observedRatio) {
                this.currentEstimation = currentEstimation;
                this.observedRatio = observedRatio;
            }
        }

        // If currentEstimation is smaller than observedRatio, the updatedCompressionRatio is currentEstimation plus
        // COMPRESSION_RATIO_DETERIORATE_STEP 0.05, otherwise currentEstimation minus COMPRESSION_RATIO_IMPROVING_STEP
        // 0.005. There are four cases,and updatedCompressionRatio shouldn't smaller than observedRatio in all of cases.
        // Refer to non test code for more details.
        List<EstimationsObservedRatios> estimationsObservedRatios = Arrays.asList(
            new EstimationsObservedRatios(0.8f, 0.84f),
            new EstimationsObservedRatios(0.6f, 0.7f),
            new EstimationsObservedRatios(0.6f, 0.4f),
            new EstimationsObservedRatios(0.004f, 0.001f));
        for (EstimationsObservedRatios estimationsObservedRatio : estimationsObservedRatios) {
            String topic = "tp";
            CompressionRatioEstimator.setEstimation(topic, CompressionType.ZSTD, estimationsObservedRatio.currentEstimation);
            float updatedCompressionRatio = CompressionRatioEstimator.updateEstimation(topic, CompressionType.ZSTD, estimationsObservedRatio.observedRatio);
            assertTrue(updatedCompressionRatio >= estimationsObservedRatio.observedRatio);
        }
    }