@Override
    public List<METRICS> read() {
        try {
            return buffer.values().stream().collect(Collectors.toList());
        } finally {
            buffer.clear();
        }
    }
Accept the data into the cache and merge with the existing value.

This method is not thread safe, should avoid concurrency calling.

@param data to be added potentially.
oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/analysis/data/MergableBufferedData.java