11. Cassandra 的部分实现分析

数据库的选择性加载

1.1 条件控制注解定义

通过对 @ConditionalOnProperty 的二次封装，进行控制底层数据库实现上的选择控制

/**
* Copyright © 2016-2022 The Thingsboard Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*     http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.thingsboard.server.dao.util;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
@Retention(RetentionPolicy.RUNTIME)
@ConditionalOnProperty(prefix = "database.ts_latest", value = "type", havingValue = "cassandra")
public @interface NoSqlTsLatestDao {
}

1.2 相关配置定义如下

database:
  ts_max_intervals: "${DATABASE_TS_MAX_INTERVALS:700}" # Max number of DB queries generated by single API call to fetch telemetry records
  ts:
#    type: "${DATABASE_TS_TYPE:sql}" # cassandra, sql, or timescale (for hybrid mode, DATABASE_TS_TYPE value should be cassandra, or timescale)
    type: "${DATABASE_TS_TYPE:cassandra}" # cassandra, sql, or timescale (for hybrid mode, DATABASE_TS_TYPE value should be cassandra, or timescale)
  ts_latest:
#    type: "${DATABASE_TS_LATEST_TYPE:sql}" # cassandra, sql, or timescale (for hybrid mode, DATABASE_TS_TYPE value should be cassandra, or timescale)
    type: "${DATABASE_TS_LATEST_TYPE:cassandra}" # cassandra, sql, or timescale (for hybrid mode, DATABASE_TS_TYPE value should be cassandra, or timescale)

其它代码实现

Cassandra 相关资料

Cassandra 简介

Cassandra 安装

Cassandra数据类型