@@ -18,14 +18,8 @@ To achieve absolutely no data loss, set wal_level to 2 and wal_fsync_period to 0
## Disaster Recovery
TDengine uses replication to provide high availability.
TDengine provides disaster recovery by using taosX to replicate data between two TDengine clusters which are deployed in two distant data centers. Assume there are two TDengine clusters, A and B, A is the source and B is the target, and A takes the workload of writing and querying. You can deploy `taosX` in the data center where cluster A resides in, `taosX` consumes the data written into cluster A and writes into cluster B. If the data center of cluster A is disrupted because of disaster, you can switch to cluster B to take the workload of data writing and querying, and deploy a `taosX` in the data center of cluster B to replicate data from cluster B to cluster A if cluster A has been recovered, or another cluster C if cluster A has not been recovered.
A TDengine cluster is managed by mnodes. You can configure up to three mnodes to ensure high availability. The data replication between mnode replicas is performed in a synchronous way to guarantee metadata consistency.
You can use the data replication feature of `taosX` to build more complicated disaster recovery solution.
The number of replicas for time series data in TDengine is associated with each database. There can be many databases in a cluster and each database can be configured with a different number of replicas. When creating a database, the parameter `replica` is used to specify the number of replicas. To achieve high availability, set `replica` to 3.
The number of dnodes in a TDengine cluster must NOT be lower than the number of replicas for any database, otherwise it would fail when trying to create a table.
As long as the dnodes of a TDengine cluster are deployed on different physical machines and the replica number is higher than 1, high availability can be achieved without any other assistance. For disaster recovery, dnodes of a TDengine cluster should be deployed in geographically different data centers.
Alternatively, you can use taosX to synchronize the data from one TDengine cluster to another cluster in a remote location. However, taosX is only available in TDengine enterprise version, for more information please contact tdengine.com.
taosX is only provided in TDengine enterprise edition, for more details please contact business@tdengine.com.
The `TaosConnection` class contains both an implementation of the PEP249 Connection interface (e.g., the `cursor()` method and the `close()` method) and many extensions (e.g., the `execute()`, `query()`, `schemaless_insert()`, and `subscribe()` methods).
The queried results can only be fetched once. For example, only one of `fetch_all()` and `fetch_all_into_dict()` can be used in the example above. Repeated fetches will result in an empty list.
:::
##### Use of TaosResult class
In the above example of using the `TaosConnection` class, we have shown two ways to get the result of a query: `fetch_all()` and `fetch_all_into_dict()`. In addition, `TaosResult` also provides methods to iterate through the result set by rows (`rows_iter`) or by data blocks (`blocks_iter`). Using these two methods will be more efficient in scenarios where the query has a large amount of data.
The `TaosConnection` class and the `TaosResult` class already implement all the functionality of the native interface. If you are familiar with the interfaces in the PEP249 specification, you can also use the methods provided by the `TaosCursor` class.
The TaosCursor class uses native connections for write and query operations. In a client-side multi-threaded scenario, this cursor instance must remain thread exclusive and cannot be shared across threads for use, otherwise, it will result in errors in the returned results.
:::
</TabItem>
<TabItem value="rest" label="REST connection">
##### Use of TaosRestCursor class
The `TaosRestCursor` class is an implementation of the PEP249 Cursor interface.
- `cursor.execute`: Used to execute arbitrary SQL statements.
- `cursor.rowcount` : For write operations, returns the number of successful rows written. For query operations, returns the number of rows in the result set.
- `cursor.description` : Returns the description of the field. Please refer to [TaosRestCursor](https://docs.taosdata.com/api/taospy/taosrest/cursor.html) for the specific format of the description information.
##### Use of the RestClient class
The `RestClient` class is a direct wrapper for the [REST API](/reference/rest-api). It contains only a `sql()` method for executing arbitrary SQL statements and returning the result.
@@ -99,6 +99,9 @@ The parameters described in this document by the effect that they have on the sy
## Monitoring Parameters
:::note
Please note the `taoskeeper` needs to be installed and running to create the `log` database and receiving metrics sent by `taosd` as the full monitoring solution.
@@ -13,14 +13,12 @@ taosKeeper is a tool for TDengine that exports monitoring metrics. With taosKeep
## Installation
<!-- There are two ways to install taosKeeper: -->
There are two ways to install taosKeeper:
Methods of installing taosKeeper:
<!--- Installing the official TDengine installer will automatically install taosKeeper. Please refer to [TDengine installation](/operation/pkg-install) for details. -->
- You can compile taosKeeper separately and install it. Please refer to the [taosKeeper](https://github.com/taosdata/taoskeeper) repository for details. -->
You can compile taosKeeper separately and install it. Please refer to the [taosKeeper](https://github.com/taosdata/taoskeeper) repository for details.
- Installing the official TDengine installer will automatically install taosKeeper. Please refer to [TDengine installation](/operation/pkg-install) for details.
- You can compile taosKeeper separately and install it. Please refer to the [taosKeeper](https://github.com/taosdata/taoskeeper) repository for details.
## Configuration and Launch
### Configuration
...
...
@@ -110,7 +108,7 @@ The following `launchctl` commands can help you manage taoskeeper service:
#### Launch With Configuration File
You can quickly launch taosKeeper with the following commands. If you do not specify a configuration file, `/etc/taos/keeper.toml` is used by default. If this file does not specify configurations, the default values are used.
You can quickly launch taosKeeper with the following commands. If you do not specify a configuration file, `/etc/taos/keeper.toml` is used by default. If this file does not specify configurations, the default values are used.
TDengine 灾备是通过在异地的两个数据中心中设置两个 TDengine 集群并利用 taosX 的数据复制能力来实现的。假定两个集群为集群 A 和集群 B，其中集群 A 为源集群，承担写入请求并提供查询服务。则在集群 A 所在数据中心中可以配置 taosX 利用 TDengine 提供的数据订阅能力，实时消费集群 A 中新写入的数据，并同步到集群 B。如果发生了灾难导致集群 A 所在数据中心不可用，则可以启用集群 B 作为数据写入和查询的主节点，并在集群 B 所处数据中心中配置 taosX 将数据复制到已经恢复的集群 A 或者新建的集群 C。
