private String offsetArrayToString(OffsetSync[] syncs) {
        StringBuilder stateString = new StringBuilder();
        stateString.append("[");
        for (int i = 0; i < SYNCS_PER_PARTITION; i++) {
            if (i == 0 || syncs[i] != syncs[i - 1]) {
                if (i != 0) {
                    stateString.append(",");
                }
                // Print only if the sync is interesting, a series of repeated syncs will be elided
                stateString.append(syncs[i].upstreamOffset());
                stateString.append(":");
                stateString.append(syncs[i].downstreamOffset());
            }
        }
        stateString.append("]");
        return stateString.toString();
    }
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