Skip to main content
Version: nightly

Go

GreptimeDB offers ingester libraries for high-throughput data writing. It utilizes the gRPC protocol, which supports schemaless writing and eliminates the need to create tables before writing data. For more information, refer to Automatic Schema Generation.

The Go ingester SDK provided by GreptimeDB is a lightweight, concurrent-safe library that is easy to use with the metric struct.

Installation​

Use the following command to install the GreptimeDB client library for Go:

go get -u github.com/GreptimeTeam/greptimedb-ingester-go@undefined

Import the library in your code:

import (
    greptime "github.com/GreptimeTeam/greptimedb-ingester-go"
    "github.com/GreptimeTeam/greptimedb-ingester-go/table"
    "github.com/GreptimeTeam/greptimedb-ingester-go/table/types"
)

Connect to database​

Username and password are always required to connect to GreptimeDB. For how to set authentication to GreptimeDB, see Authentication. Here we set the username and password when using the library to connect to GreptimeDB.

cfg := greptime.NewConfig("127.0.0.1").
    // change the database name to your database name
    WithDatabase("public").
    // Default port 4001
    // WithPort(4001).
    // Enable secure connection if your server is secured by TLS
    // WithInsecure(false).
    // set authentication information
    WithAuth("username", "password")

cli, _ := greptime.NewClient(cfg)

Data model​

Each row item in a table consists of three types of columns: Tag, Timestamp, and Field. For more information, see Data Model. The types of column values could be String, Float, Int, Timestamp, etc. For more information, see Data Types.

Low-level API​

The GreptimeDB low-level API provides a straightforward method to write data to GreptimeDB by adding rows to the table object with a predefined schema.

Create row objects​

This following code snippet begins by constructing a table named cpu_metric, which includes columns host, cpu_user, cpu_sys, and ts. Subsequently, it inserts a single row into the table.

The table consists of three types of columns:

  • Tag: The host column, with values of type String.
  • Field: The cpu_user and cpu_sys columns, with values of type Float.
  • Timestamp: The ts column, with values of type Timestamp.
// Construct the table schema for CPU metrics
cpuMetric, err := table.New("cpu_metric")
if err != nil {
    // Handle error appropriately
}

// Add a 'Tag' column for host identifiers
cpuMetric.AddTagColumn("host", types.STRING)
// Add a 'Timestamp' column for recording the time of data collection
cpuMetric.AddTimestampColumn("ts", types.TIMESTAMP_MILLISECOND)
// Add 'Field' columns for user and system CPU usage measurements
cpuMetric.AddFieldColumn("cpu_user", types.FLOAT)
cpuMetric.AddFieldColumn("cpu_sys", types.FLOAT)

// Insert example data
// NOTE: The arguments must be in the same order as the columns in the defined schema: host, ts, cpu_user, cpu_sys
err = cpuMetric.AddRow("127.0.0.1", time.Now(), 0.1, 0.12)
err = cpuMetric.AddRow("127.0.0.1", time.Now(), 0.11, 0.13)
if err != nil {
    // Handle error appropriately
}

To improve the efficiency of writing data, you can create multiple rows at once to write to GreptimeDB.

cpuMetric, err := table.New("cpu_metric")
if err != nil {
    // Handle error appropriately
}
cpuMetric.AddTagColumn("host", types.STRING)
cpuMetric.AddTimestampColumn("ts", types.TIMESTAMP_MILLISECOND)
cpuMetric.AddFieldColumn("cpu_user", types.FLOAT)
cpuMetric.AddFieldColumn("cpu_sys", types.FLOAT)
err = cpuMetric.AddRow("127.0.0.1", time.Now(), 0.1, 0.12)
if err != nil {
    // Handle error appropriately
}

memMetric, err := table.New("mem_metric")
if err != nil {
    // Handle error appropriately
}
memMetric.AddTagColumn("host", types.STRING)
memMetric.AddTimestampColumn("ts", types.TIMESTAMP_MILLISECOND)
memMetric.AddFieldColumn("mem_usage", types.FLOAT)
err = memMetric.AddRow("127.0.0.1", time.Now(), 112)
if err != nil {
    // Handle error appropriately
}

Insert data​

The following example shows how to insert rows to tables in GreptimeDB.

resp, err := cli.Write(context.Background(), cpuMetric, memMetric)
if err != nil {
    // Handle error appropriately
}
log.Printf("affected rows: %d\n", resp.GetAffectedRows().GetValue())

Streaming insert​

Streaming insert is useful when you want to insert a large amount of data such as importing historical data.

err := cli.StreamWrite(context.Background(), cpuMetric, memMetric)
if err != nil {
    // Handle error appropriately
}

Close the stream writing after all data has been written. In general, you do not need to close the stream writing when continuously writing data.

affected, err := cli.CloseStream(ctx)

High-level API​

The high-level API uses an ORM style object to write data to GreptimeDB. It allows you to create, insert, and update data in a more object-oriented way, providing developers with a friendlier experience. However, it is not as efficient as the low-level API. This is because the ORM style object may consume more resources and time when converting the objects.

Create row objects​

type CpuMetric struct {
    Host            string    `greptime:"tag;column:host;type:string"`
    CpuUser         float64   `greptime:"field;column:cpu_user;type:float64"`
    CpuSys          float64   `greptime:"field;column:cpu_sys;type:float64"`
    Ts              time.Time `greptime:"timestamp;column:ts;type:timestamp;precision:millisecond"`
}

func (CpuMetric) TableName() string {
	return "cpu_metric"
}

cpuMetrics := []CpuMetric{
    {
        Host:        "127.0.0.1",
        CpuUser:     0.10,
        CpuSys:      0.12,
        Ts:          time.Now(),
    }
}

Insert data​

resp, err := cli.WriteObject(context.Background(), cpuMetrics)
log.Printf("affected rows: %d\n", resp.GetAffectedRows().GetValue())

Streaming insert​

Streaming insert is useful when you want to insert a large amount of data such as importing historical data.

err := cli.StreamWriteObject(context.Background(), cpuMetrics)

Close the stream writing after all data has been written. In general, you do not need to close the stream writing when continuously writing data.

affected, err := cli.CloseStream(ctx)

More examples​

For fully runnable code snippets and explanations for common methods, see the Examples.

Ingester library reference​