Go Flight client

Apache Arrow for Go integrates with Go scripts and applications to query data stored in InfluxDB.

Flight SQL client

Example query using Flight SQL

The following example shows how to use the Arrow Flight SQL client for Go to query an InfluxDB Clustered database:

1. In your editor, open a new file named query.go and enter the following sample code:

   package main
   
   import (
     "context"
     "crypto/x509"
     "encoding/json"
     "fmt"
     "os"
   
     "github.com/apache/arrow/go/v14/arrow/flight/flightsql"
     "google.golang.org/grpc"
     "google.golang.org/grpc/credentials"
     "google.golang.org/grpc/metadata"
   )
   
   func dbQuery(ctx context.Context) error {
     url := "cluster-host.com:443"
   
     // INFLUX_TOKEN is an environment variable you created for your database READ token
     token := os.Getenv("INFLUX_TOKEN")
     database := "get-started"
   
     // Create a gRPC transport
     pool, err := x509.SystemCertPool()
     if err != nil {
       return fmt.Errorf("x509: %s", err)
     }
     transport := grpc.WithTransportCredentials(credentials.NewClientTLSFromCert(pool, ""))
     opts := []grpc.DialOption{
       transport,
     }
   
     // Create query client
     client, err := flightsql.NewClient(url, nil, nil, opts...)
     if err != nil {
       return fmt.Errorf("flightsql: %s", err)
     }
   
     ctx = metadata.AppendToOutgoingContext(ctx, "authorization", "Bearer "+token)
     ctx = metadata.AppendToOutgoingContext(ctx, "database", database)
   
     // Execute query
     query := `SELECT
       *
     FROM
       home
     WHERE
       time >= '2022-01-01T08:00:00Z'
       AND time <= '2022-01-01T20:00:00Z'`
   
     info, err := client.Execute(ctx, query)
     if err != nil {
       return fmt.Errorf("flightsql flight info: %s", err)
     }
     reader, err := client.DoGet(ctx, info.Endpoint[0].Ticket)
     if err != nil {
       return fmt.Errorf("flightsql do get: %s", err)
     }
   
     // Print results as JSON
     for reader.Next() {
       record := reader.Record()
       b, err := json.MarshalIndent(record, "", "  ")
       if err != nil {
         return err
       }
       fmt.Println("RECORD BATCH")
       fmt.Println(string(b))
   
       if err := reader.Err(); err != nil {
         return fmt.Errorf("flightsql reader: %s", err)
       }
     }
   
     return nil
   }
   
   func main() {
     if err := dbQuery(context.Background()); err != nil {
       fmt.Fprintf(os.Stderr, "error: %v\n", err)
       os.Exit(1)
     }
   }
   

   The sample does the following:

   1. Imports the following packages:

      • context
      • crypto/x509
      • encoding/json
      • fmt
      • os
      • github.com/apache/arrow/go/v14/arrow/flight/flightsql
      • google.golang.org/grpc
      • google.golang.org/grpc/credentials
      • google.golang.org/grpc/metadata

   2. Creates a dbQuery function that does the following:

      1. Defines variables for InfluxDB credentials.

         • url: InfluxDB cluster hostname and port (:443) (no protocol)
         • database: the name of the InfluxDB Clustered database to query
         • token: a database token with read permission on the specified database. For security reasons, we recommend setting this as an environment variable rather than including the raw token string.

      2. Defines an opts options list that includes a gRPC transport for communicating with InfluxDB over the gRPC+TLS protocol.

      3. Calls the flightsql.NewClient() method with url and opts to create a new Flight SQL client.

      4. Appends the following InfluxDB credentials as key-value pairs to the outgoing context:

         • authorization: Bearer <INFLUX_TOKEN>
         • database: Database name

      5. Defines the SQL query to execute.

      6. Calls the client.execute() method to send the query request.

      7. Calls the client.doGet() method with the ticket from the query response to retrieve result data from the endpoint.

      8. Creates a reader to read the Arrow table returned by the endpoint and print the results as JSON.

   3. Creates a main module function that executes the dbQuery function.

2. Enter the following commands to install all the necessary packages and run the program to query InfluxDB Clustered:

   go get ./...
   go run ./query.go
   

RECORD BATCH
[
  {
    "co": 0,
    "hum": 35.9,
    "room": "Kitchen",
    "temp": 21,
    "time": "2022-01-01 08:00:00"
  },
  {
    "co": 0,
    "hum": 36.2,
    "room": "Kitchen",
    "temp": 23,
    "time": "2022-01-01 09:00:00"
  },
  {
    "co": 0,
    "hum": 36.1,
    "room": "Kitchen",
    "temp": 22.7,
    "time": "2022-01-01 10:00:00"
  },
  {
    "co": 0,
    "hum": 36,
    "room": "Kitchen",
    "temp": 22.4,
    "time": "2022-01-01 11:00:00"
  },
  {
    "co": 0,
    "hum": 36,
    "room": "Kitchen",
    "temp": 22.5,
    "time": "2022-01-01 12:00:00"
  },
  ...
]

For more information, see the Go Arrow Flight Client documentation.