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KraftCloud

Deploy DuckDB with a Go Web Server

This guide shows you how to use DuckDB, an in-process SQL OLAP database management system, in your Go project.

To run it example, follow these steps:

  1. Install the kraft CLI tool and a container runtime engine, e.g. Docker.

  2. Clone the examples repository and cd into the examples/duckdb-go/ directory:

Terminal window
git clone https://github.com/kraftcloud/examples
cd examples/duckdb-go/

Make sure to log into KraftCloud by setting your token and a metro close to you. We use fra0 (Frankfurt, 🇩🇪) in this guide:

Terminal window
# Set KraftCloud access token
export KRAFTCLOUD_TOKEN=token
# Set metro to Frankfurt, DE
export KRAFTCLOUD_METRO=fra0

When done, invoke the following command to deploy this application on KraftCloud:

Terminal window
kraft cloud deploy -p 443:8080 .

The output shows the instance URL and other details:

Terminal window
[●] Deployed successfully!
 │
 ├────────── name: duckdb-go-qfd8x
 ├────────── uuid: 90960d27-458b-4dd7-a037-2a9a3a47f095
 ├───────── state: running
 ├─────────── url: https://autumn-gorilla-hg4h6sup.fra0.kraft.host
 ├───────── image: duckdb-go@sha256:6999293f8694ac00beb6a1d639fab8f96f78c2e6ecb8ccb2311539908895a699
 ├───── boot time: 32.12 ms
 ├──────── memory: 128 MiB
 ├─ service group: autumn-gorilla-hg4h6sup
 ├── private fqdn: duckdb-go-qfd8x.internal
 ├──── private ip: 172.16.6.2
 └────────── args: /server

In this case, the instance name is duckdb-go-qfd8x and the URL is https://autumn-gorilla-hg4h6sup.fra0.kraft.host. They are different for each run.

Use curl to query the KraftCloud instance of DuckDB.

Terminal window
curl https://autumn-gorilla-hg4h6sup.fra0.kraft.host
Terminal window
id: %d, name: %s 42 John

At any point in time, you can list information about the instance:

Terminal window
kraft cloud instance list
NAME               FQDN                              STATE    CREATED AT    IMAGE                            MEMORY   ARGS      BOOT TIME
duckdb-go-qfd8x    autumn-gorilla-hg4h6sup.fra0.k... running  1 minute ago  felipe.unikraft.io/duckdb-go...  128 MiB  /server   32118us

When done, you can remove the instance:

Terminal window
kraft cloud instance remove duckdb-go-qfd8x

Customize your Application

To customize the application, update the files in the repository, listed below:

  • src/main.go: the Go web server frontend
  • Kraftfile: the KraftCloud specification, including command-line arguments
  • Dockerfile: the Docker-specified application filesystem
package main


import (
   "database/sql"
   "fmt"
   "net/http"


   _ "github.com/marcboeker/go-duckdb"
)


func main() {
   db, _ := sql.Open("duckdb", "")


   db.Exec(`CREATE TABLE person (id INTEGER, name VARCHAR)`)
   db.Exec(`INSERT INTO person VALUES (42, 'John')`)


   var (
     id   int
     name string
   )
   row := db.QueryRow(`SELECT id, name FROM person`)
   _ = row.Scan(&id, &name)
   fmt.Println("id:", id, "name:", name)


   // Serve the print on port 8080 as a http server
   http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
     fmt.Fprintln(w, "id: %d, name: %s", id, name)
   })
   http.ListenAndServe(":8080", nil)
}

The following options are available for customizing the application:

  • If only updating the implementation in the main.go source file, no other change is required.

  • If new files are added, these have to be copied in the application filesystem, using the COPY command in the Dockerfile.

  • If new source code files are added, they have to be built using the corresponding go build command.

  • If a new executable is built, update the cmd line in the Kraftfile and replace /server with the path to the new executable.

  • More extensive changes may require expanding the Dockerfile with additional Dockerfile commands.

Learn More

Use the --help option for detailed information on using KraftCloud:

Terminal window
kraft cloud --help

Or visit the CLI Reference.