private OffsetSync[] updateExistingSyncs(OffsetSync[] syncs, OffsetSync offsetSync) {
        // Make a copy of the array before mutating it, so that readers do not see inconsistent data
        // TODO: consider batching updates so that this copy can be performed less often for high-volume sync topics.
        OffsetSync[] mutableSyncs = Arrays.copyOf(syncs, SYNCS_PER_PARTITION);
        updateSyncArray(mutableSyncs, syncs, offsetSync);
        if (log.isTraceEnabled()) {
            log.trace("New sync {} applied, new state is {}", offsetSync, offsetArrayToString(mutableSyncs));
        }
        return mutableSyncs;
    }
Start the OffsetSyncStore, blocking until all previous Offset Syncs have been read from backing storage.
connect/mirror/src/main/java/org/apache/kafka/connect/mirror/OffsetSyncStore.java