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Connecting to TDengine /developer-guide/connecting-to-tdengine

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TDengine provides a rich set of application development interfaces. To facilitate users in quickly developing their applications, TDengine supports connectors for multiple programming languages. The official connectors include support for C/C++, Java, Python, Go, Node.js, C#, Rust, Lua (community contribution), and PHP (community contribution). These connectors support connecting to the TDengine cluster using the native interface (taosc) and REST interface (not supported in some languages yet). Community developers have also contributed several unofficial connectors, such as ADO.NET connector, Lua connector, and PHP connector. Additionally, TDengine can directly call the REST API provided by taosadapter for data writing and querying operations.

Connection Methods

TDengine provides three methods for establishing connections:

  1. Direct connection between the client driver taosc and the server program taosd, referred to as "native connection" in the text below.
  2. Connection to taosd through the REST API provided by the taosAdapter component, referred to as "REST connection" in the text below.
  3. Connection to taosd through the WebSocket API provided by the taosAdapter component, referred to as "WebSocket connection" in the text below.
Connecting to TDengine
Figure 1. Connecting to TDengine

Regardless of the method used to establish the connection, the connectors provide the same or similar API to operate the database and can execute SQL statements. The initialization of the connection slightly differs, but users will not feel any difference in usage. For various connection methods and language connector support, please refer to: Connector Features

Key differences include:

  1. Using native connection requires ensuring that the client driver taosc and the server's TDengine version are compatible.
  2. Using REST connection does not require installing the client driver taosc, offering the advantage of cross-platform ease of use, but it lacks features like data subscription and binary data types. Additionally, compared to native and WebSocket connections, the performance of REST connections is the lowest. REST interfaces are stateless. When using REST connections, it is necessary to specify the database names of tables and supertables in SQL.
  3. Using WebSocket connection also does not require installing the client driver taosc.
  4. Connecting to cloud service instances must use REST connection or WebSocket connection.

WebSocket connection is recommended

Installing the Client Driver taosc

If you choose a native connection and your application is not running on the same server as TDengine, you need to install the client driver first; otherwise, you can skip this step. To avoid incompatibility between the client driver and the server, please use consistent versions.

Installation Steps

Installation Verification

After completing the above installation and configuration, and confirming that the TDengine service has started running normally, you can log in using the TDengine command-line program taos included in the installation package.

Installing Connectors

If you are using Maven to manage your project, simply add the following dependency to your pom.xml.

<dependency>
  <groupId>com.taosdata.jdbc</groupId>
  <artifactId>taos-jdbcdriver</artifactId>
  <version>3.5.2</version>
</dependency>

  • Pre-installation Preparation

    • Install Python. Recent versions of the taospy package require Python 3.6.2+. Earlier versions of the taospy package require Python 3.7+. The taos-ws-py package requires Python 3.7+. If Python is not already installed on your system, refer to Python BeginnersGuide for installation.
    • Install pip. In most cases, the Python installation package comes with the pip tool; if not, refer to the pip documentation for installation.
    • If using a native connection, you also need to install the client driver. The client software package includes the TDengine client dynamic link library (libtaos.so or taos.dll) and TDengine CLI.

  • Using pip to Install

    • Uninstall old versions If you have previously installed old versions of the Python connector, please uninstall them first.
    pip3 uninstall taos taospy
pip3 uninstall taos  taos-ws-py

    • Install taospy

      • Latest version
      pip3 install taospy
      • Install a specific version
      pip3 install taospy==2.3.0
      • Install from GitHub
      pip3 install git+https://github.com/taosdata/taos-connector-python.git

      Note: This package is for native connection

    • Install taos-ws-py

    pip3 install taos-ws-py

    Note: This package is for WebSocket connection

    • Install both taospy and taos-ws-py
    pip3 install taospy[ws]

  • Installation Verification

For native connections, it is necessary to verify that both the client driver and the Python connector itself are correctly installed. If the taos module can be successfully imported, then the client driver and Python connector are correctly installed. You can enter in the Python interactive Shell:

import taos
For REST connections, you only need to verify if the `taosrest` module can be successfully imported. You can enter in the Python interactive Shell: 
import taosrest

For WebSocket connections, you only need to verify if the taosws module can be successfully imported. You can enter in the Python interactive Shell:

import taosws

Edit go.mod to add the driver-go dependency.

module goexample

go 1.17

require github.com/taosdata/driver-go/v3 latest

:::note

driver-go uses cgo to wrap the taosc API. cgo requires GCC to compile C source code. Therefore, make sure GCC is installed on your system.

:::

Edit Cargo.toml to add the taos dependency.

[dependencies]
taos = { version = "*"}

:::info

The Rust connector distinguishes different connection methods through different features. It supports both native and WebSocket connections by default. If only a WebSocket connection is needed, set the ws feature:

taos = { version = "*", default-features = false, features = ["ws"] }

:::

  • Pre-installation Preparation

    • Install the Node.js development environment, using version 14 or above. Download link: https://nodejs.org/en/download/

  • Installation

    • Use npm to install the Node.js connector
    npm install @tdengine/websocket

    Note: Node.js currently only supports WebSocket connections

  • Installation Verification

    • Create a verification directory, for example: ~/tdengine-test, download the nodejsChecker.js source code from GitHub to local.
    • Execute the following commands in the command line.
    npm init -y
npm install @tdengine/websocket
node nodejsChecker.js
    • After performing the above steps, the command line will output the results of nodeChecker.js connecting to the TDengine instance and performing simple insertion and query operations.

Edit the project configuration file to add a reference to TDengine.Connector:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net6.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
    <StartupObject>TDengineExample.AsyncQueryExample</StartupObject>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="TDengine.Connector" Version="3.1.0" />
  </ItemGroup>

</Project>

You can also add it via the dotnet command:

dotnet add package TDengine.Connector

:::note

The following example code is based on dotnet6.0. If you are using another version, you may need to make appropriate adjustments.

:::

If you have already installed the TDengine server software or the TDengine client driver taosc, then the C connector is already installed and no additional action is required.

To access TDengine using the REST API method, no drivers or connectors need to be installed.

Establishing Connection

Before proceeding with this step, please ensure that there is a running TDengine that can be accessed, and that the server's FQDN is configured correctly. The following example code assumes that TDengine is installed on the local machine, and that the FQDN (default localhost) and serverPort (default 6030) are using the default configuration.

Connection Parameters

There are many configuration options for connecting, so before establishing a connection, let's first introduce the parameters used by the connectors of each language to establish a connection.

The parameters for establishing a connection with the Java connector are URL and Properties.
The JDBC URL format for TDengine is: jdbc:[TAOS|TAOS-WS|TAOS-RS]://[host_name]:[port]/[database_name]?[user={user}|&password={password}|&charset={charset}|&cfgdir={config_dir}|&locale={locale}|&timezone={timezone}|&batchfetch={batchfetch}]

For detailed explanations of URL and Properties parameters and how to use them, see URL specifications

The Python connector uses the connect() method to establish a connection, here are the specific parameters for the connection:

  • url: URL of the taosAdapter REST service. The default is port 6041 on localhost.
  • user: TDengine username. The default is root.
  • password: TDengine user password. The default is taosdata.
  • timeout: HTTP request timeout in seconds. The default is socket._GLOBAL_DEFAULT_TIMEOUT. Generally, no configuration is needed.

The data source name has a generic format, similar to PEAR DB, but without the type prefix (brackets indicate optional):

[username[:password]@][protocol[(address)]]/[dbname][?param1=value1&...&paramN=valueN]

Complete DSN format:

username:password@protocol(address)/dbname?param=value

Supported DSN parameters are as follows:

Native connection:

  • cfg specifies the taos.cfg directory
  • cgoThread specifies the number of cgo operations that can be executed concurrently, default is the number of system cores
  • cgoAsyncHandlerPoolSize specifies the size of the async function handler, default is 10000

REST connection:

  • disableCompression whether to accept compressed data, default is true which means not accepting compressed data, set to false if data transmission uses gzip compression.
  • readBufferSize the size of the buffer for reading data, default is 4K (4096), this value can be increased appropriately when the query result data volume is large.
  • token the token used when connecting to cloud services.
  • skipVerify whether to skip certificate verification, default is false which means not skipping certificate verification, set to true if connecting to an insecure service.

WebSocket connection:

  • enableCompression whether to send compressed data, default is false which means not sending compressed data, set to true if data transmission uses compression.
  • readTimeout the timeout for reading data, default is 5m.
  • writeTimeout the timeout for writing data, default is 10s.

Rust connector uses DSN to create connections, the basic structure of the DSN description string is as follows:

<driver>[+<protocol>]://[[<username>:<password>@]<host>:<port>][/<database>][?<p1>=<v1>[&<p2>=<v2>]]
|------|------------|---|-----------|-----------|------|------|------------|-----------------------|
|driver|   protocol |   | username  | password  | host | port |  database  |  params               |

For detailed explanation of DSN and how to use it, see Connection Features

Node.js connector uses DSN to create connections, the basic structure of the DSN description string is as follows: 
[+<protocol>]://[[<username>:<password>@]<host>:<port>][/<database>][?<p1>=<v1>[&<p2>=<v2>]]
|------------|---|-----------|-----------|------|------|------------|-----------------------|
|   protocol |   | username  | password  | host | port |  database  |  params               |

  • protocol: Establish a connection using the websocket protocol. For example, ws://localhost:6041

  • username/password: Username and password for the database.

  • host/port: Host address and port number. For example, localhost:6041

  • database: Database name.

  • params: Other parameters. For example, token.

  • Complete DSN example:

    ws://root:taosdata@localhost:6041

ConnectionStringBuilder uses a key-value pair method to set connection parameters, where key is the parameter name and value is the parameter value, separated by a semicolon ;.

For example:

"protocol=WebSocket;host=127.0.0.1;port=6041;useSSL=false"

Supported parameters are as follows:

  • host: The address of the TDengine instance.
  • port: The port of the TDengine instance.
  • username: Username for the connection.
  • password: Password for the connection.
  • protocol: Connection protocol, options are Native or WebSocket, default is Native.
  • db: Database to connect to.
  • timezone: Time zone, default is the local time zone.
  • connTimeout: Connection timeout, default is 1 minute.

Additional parameters supported for WebSocket connections:

  • readTimeout: Read timeout, default is 5 minutes.
  • writeTimeout: Send timeout, default is 10 seconds.
  • token: Token for connecting to TDengine cloud.
  • useSSL: Whether to use SSL connection, default is false.
  • enableCompression: Whether to enable WebSocket compression, default is false.
  • autoReconnect: Whether to automatically reconnect, default is false.
  • reconnectRetryCount: Number of retries for reconnection, default is 3.
  • reconnectIntervalMs: Reconnection interval in milliseconds, default is 2000.

WebSocket Connection

For C/C++ language connectors, the WebSocket connection uses the ws_connect() function to establish a connection with the TDengine database. Its parameter is a DSN description string, structured as follows:

<driver>[+<protocol>]://[[<username>:<password>@]<host>:<port>][/<database>][?<p1>=<v1>[&<p2>=<v2>]]
|------|------------|---|-----------|-----------|------|------|------------|-----------------------|
|driver|   protocol |   | username  | password  | host | port |  database  |  params               |

For detailed explanation of DSN and how to use it, see Connection Features

Native Connection

For C/C++ language connectors, the native connection method uses the taos_connect() function to establish a connection with the TDengine database. Detailed parameters are as follows:

  • host: Hostname or IP address of the database server to connect to. If it is a local database, "localhost" can be used.
  • user: Username for logging into the database.
  • passwd: Password corresponding to the username.
  • db: Default database name when connecting. If no database is specified, pass NULL or an empty string.
  • port: Port number the database server listens on. The default port number is 6030.

The taos_connect_auth() function is also provided for establishing a connection with the TDengine database using an MD5 encrypted password. This function is similar to taos_connect, but differs in the handling of the password, as taos_connect_auth requires the MD5 encrypted string of the password.

When accessing TDengine via REST API, the application directly establishes an HTTP connection with taosAdapter, and it is recommended to use a connection pool to manage connections.

For specific parameters using the REST API, refer to: HTTP request format

WebSocket Connection

Below are code examples for establishing WebSocket connections in various language connectors. It demonstrates how to connect to the TDengine database using WebSocket and set some parameters for the connection. The whole process mainly involves establishing the database connection and handling exceptions.

{{#include docs/examples/java/src/main/java/com/taos/example/WSConnectExample.java:main}}

{{#include docs/examples/python/connect_websocket_examples.py:connect}}

{{#include docs/examples/go/connect/wsexample/main.go}}

{{#include docs/examples/rust/restexample/examples/connect.rs}}

{{#include docs/examples/node/websocketexample/sql_example.js:createConnect}}

{{#include docs/examples/csharp/wsConnect/Program.cs:main}}

{{#include docs/examples/c-ws/connect_example.c}}

Not supported

Native Connection

Below are examples of code for establishing native connections in various languages. It demonstrates how to connect to the TDengine database using a native connection method and set some parameters for the connection. The entire process mainly involves establishing a database connection and handling exceptions.

{{#include docs/examples/java/src/main/java/com/taos/example/JNIConnectExample.java:main}}

{{#include docs/examples/go/connect/cgoexample/main.go}}

{{#include docs/examples/rust/nativeexample/examples/connect.rs}}

Not supported

{{#include docs/examples/csharp/connect/Program.cs:main}}

Not supported

REST Connection

Below are examples of code for establishing REST connections in various languages. It demonstrates how to connect to the TDengine database using a REST connection method. The entire process mainly involves establishing a database connection and handling exceptions.

{{#include docs/examples/java/src/main/java/com/taos/example/RESTConnectExample.java:main}}

{{#include docs/examples/python/connect_rest_example.py:connect}}

{{#include docs/examples/go/connect/restexample/main.go}}

Not supported

Not supported

Not supported

Not supported

Access TDengine using the REST API method, where the application independently establishes an HTTP connection.

:::tip If the connection fails, in most cases it is due to incorrect FQDN or firewall settings. For detailed troubleshooting methods, please see "Encountering the error 'Unable to establish connection, what should I do?'" in the "Common Questions and Feedback".

:::

Connection Pool

Some connectors offer a connection pool, or can be used in conjunction with existing connection pool components. By using a connection pool, applications can quickly obtain available connections from the pool, avoiding the overhead of creating and destroying connections with each operation. This not only reduces resource consumption but also improves response speed. Additionally, connection pools support the management of connections, such as limiting the maximum number of connections and checking the validity of connections, ensuring efficient and reliable use of connections. We recommend managing connections using a connection pool.
Below are code examples of connection pool support for various language connectors.

HikariCP

Example usage is as follows:

{{#include docs/examples/java/src/main/java/com/taos/example/HikariDemo.java:connection_pool}}

After obtaining a connection through HikariDataSource.getConnection(), you need to call the close() method after use, which actually does not close the connection but returns it to the pool. For more issues about using HikariCP, please see the official documentation.

Druid

Example usage is as follows:

{{#include docs/examples/java/src/main/java/com/taos/example/DruidDemo.java:connection_pool}}

For more issues about using Druid, please see the official documentation.

Using sql.Open creates a connection that has already implemented a connection pool, and you can set connection pool parameters through the API, as shown in the example below

{{#include docs/examples/go/connect/connpool/main.go:pool}}

In complex applications, it is recommended to enable connection pooling. The connection pool for [taos] by default (in asynchronous mode) is implemented using [deadpool].

Below, you can create a connection pool with default parameters.

let pool: Pool<TaosBuilder> = TaosBuilder::from_dsn("taos:///")
    .unwrap()
    .pool()
    .unwrap();

You can also use the connection pool builder to set the connection pool parameters:

let pool: Pool<TaosBuilder> = Pool::builder(Manager::from_dsn(self.dsn.clone()).unwrap().0)
    .max_size(88)  // Maximum number of connections
    .build()
    .unwrap();

In your application code, use pool.get()? to obtain a connection object [Taos].

let taos = pool.get()?;