TDengine Connectors for Node.js

This repository includes two Node connector for TDengine. One is @tdengine/client, a Node.js connector using TDengine's native connection. Another is @tdengine/rest, a TypeScript connector using TDengine's rest connection.

This readme file introduce basic installation and work with our connectors.

@tdengine/client

This is the Node.js library that lets you connect to TDengine 3.0 version. It is built so that you can use as much of it as you want or as little of it as you want through providing an extensive API. If you want the raw data in the form of an array of arrays for the row data retrieved from a table, you can do that. If you want to wrap that data with objects that allow you easily manipulate and display data such as using a prettifier function, you can do that!

Installation

To get started, just type in the following to install the connector through npm

npm install @tdengine/client

To interact with TDengine, we make use of the node-gyp library. To install, you will need to install the following depending on platform (the following instructions are quoted from node-gyp)

On Linux

• python
• make
• A proper C/C++ compiler toolchain, like GCC
• node (either v10.x or v12.x, other version has some dependency compatibility problems)

On Windows

Option 1

Install all the required tools and configurations using Microsoft's windows-build-tools using npm install --global --production windows-build-tools from an elevated PowerShell or CMD.exe (run as Administrator).

Option 2

Install tools and configuration manually:

• Install Visual C++ Build Environment: Visual Studio Build Tools (using "Visual C++ build tools" workload) or Visual Studio 2017 Community (using the "Desktop development with C++" workload)
• Install Python 2.7 (v3.x.x is not supported), and run npm config set python python2.7 (or see below for further instructions on specifying the proper Python version and path.)
• Launch cmd, npm config set msvs_version 2017

If the above steps didn't work for you, please visit Microsoft's Node.js Guidelines for Windows for additional tips.

To target native ARM64 Node.js on Windows 10 on ARM, add the components "Visual C++ compilers and libraries for ARM64" and "Visual C++ ATL for ARM64".

Usage

The following is a short summary of the basic usage of the connector, the full api and documentation can be found here

Connection

To use the connector, first require the library @tdengine/client. Running the function taos.connect with the connection options passed in as an object will return a TDengine connection object. The required connection option is host, other options if not set, will be the default values as shown below.

A cursor also needs to be initialized in order to interact with TDengine from Node.js.

const taos = require('@tdengine/client');
var conn = taos.connect({host:"127.0.0.1", user:"root", password:"taosdata", config:"/etc/taos",port:0})
var cursor = conn.cursor(); // Initializing a new cursor

Close a connection

conn.close();

Queries

We can now start executing simple queries through the cursor.query function, which returns a TaosQuery object.

var query = cursor.query('show databases;')

We can get the results of the queries through the query.execute() function, which returns a promise that resolves with a TaosResult object, which contains the raw data and additional functionalities such as pretty printing the results.

var promise = query.execute();
promise.then(function(result) {
  result.pretty(); //logs the results to the console as if you were in the taos shell
});

You can also query by binding parameters to a query by filling in the question marks in a string as so. The query will automatically parse what was binded and convert it to the proper format for use with TDengine

var query = cursor.query('select * from meterinfo.meters where ts <= ? and areaid = ?;').bind(new Date(), 5);
query.execute().then(function(result) {
  result.pretty();
})

The TaosQuery object can also be immediately executed upon creation by passing true as the second argument, returning a promise instead of a TaosQuery.

var promise = cursor.query('select * from meterinfo.meters where v1 = 30;', true)
promise.then(function(result) {
  result.pretty();
})

If you want to execute queries without objects being wrapped around the data, use cursor.execute() directly and cursor.fetchall() to retrieve data if there is any.

cursor.execute('select count(*), avg(v1), min(v2) from meterinfo.meters where ts >= \"2019-07-20 00:00:00.000\";');
var data = cursor.fetchall();
console.log(cursor.fields); // Latest query's Field metadata is stored in cursor.fields
console.log(cursor.data); // Latest query's result data is stored in cursor.data, also returned by fetchall.

Async functionality

Async queries can be performed using the same functions such as cursor.execute, TaosQuery.query, but now with _a appended to them.

Say you want to execute an two async query on two separate tables, using cursor.query, you can do that and get a TaosQuery object, which upon executing with the execute_a function, returns a promise that resolves with a TaosResult object.

var promise1 = cursor.query('select count(*), avg(v1), avg(v2) from meter1;').execute_a()
var promise2 = cursor.query('select count(*), avg(v1), avg(v2) from meter2;').execute_a();
promise1.then(function(result) {
  result.pretty();
})
promise2.then(function(result) {
  result.pretty();
})

@tdengine/rest

This is a TDengine's RESTful connector in TypeScript. It's depend on node-fetch v2. Using fetch(url,options) to send sql statement and receive response.

Installation

npm i @tdengine/rest

Usage

import { options, connect } from '@tdengine/rest'
options.path='/rest/sql';
// set host
options.host='localhost';
// set other options like user/passwd

let conn = connect(options);
let cursor = conn.cursor();
(async()=>{
    let result = await cursor.query('show databases');

    // Get Result object, return Result object.
    console.log(result.getResult());
    // Get status, return 'succ'|'error'.
    console.log(result.getStatus());
    // Get head,return response head (Array<any>|undefined,when execute failed this is undefined).
    console.log(result.getHead());
    // Get Meta data, return Meta[]|undefined(when execute failed this is undefined).
    console.log(result.getMeta());
    // Get data,return Array<Array<any>>|undefined(when execute failed this is undefined).
    console.log(result.getData());
    // Get affect rows,return number|undefined(when execute failed this is undefined).
    console.log(result.getAffectRows());
    // Get command,return SQL send to server(need to `query(sql,false)`,set 'pure=false',default true).
    console.log(result.getCommand());
    // Get error code ,return number|undefined(when execute failed this is undefined).
    console.log(result.getErrCode());
    // Get error string,return string|undefined(when execute failed this is undefined).
    console.log(result.getErrStr());
})()