public MongoClient getOrCreateMongoClient(MongoDBSourceConfig sourceConfig) {
        return pools.computeIfAbsent(
                sourceConfig.getConnectionString(),
                rawConnectionString -> {
                    ConnectionString connectionString = new ConnectionString(rawConnectionString);
                    LOG.info(
                            "Create and register mongo client {}@{}",
                            connectionString.getUsername(),
                            connectionString.getHosts());
                    return MongoClients.create(connectionString);
                });
    }
A MongoDB Client pools.
Copy from com.ververica:flink-connector-mongodb-cdc:2.3.0.
inlong-sort/sort-flink/sort-flink-v1.13/sort-connectors/mongodb-cdc/src/main/java/org/apache/inlong/sort/cdc/mongodb/source/connection/MongoClientPool.java