Build a Go App with CockroachDB and GORM

Warning:
Cockroach Labs will stop providing Assistance Support for this version on May 10, 2022. Prior to that date, upgrade to a more recent version to continue receiving support. For more details, see the Release Support Policy.

This tutorial shows you how build a simple CRUD Go application with CockroachDB and the GORM ORM.

Tip:

For another use of GORM with CockroachDB, see our examples-orms repository.

Step 1. Start CockroachDB

Create a free cluster

  1. If you haven't already, sign up for a CockroachDB Cloud account.
  2. Log in to your CockroachDB Cloud account.
  3. On the Clusters page, click Create Cluster.
  4. On the Create your cluster page, select CockroachDB Serverless.

    Note:

    This cluster will be free forever.

  5. Click Create your free cluster.

Your cluster will be created in approximately 20-30 seconds.

Set up your cluster connection

  1. Navigate to the cluster's SQL Users page, and create a new user, with a new password.

  2. Navigate to the Cluster Overview page, select Connect, and, under the Connection String tab, download the cluster certificate.

  3. Take note of the connection string provided. You'll use it to connect to the database later in this tutorial.

  1. If you haven't already, download the CockroachDB binary.
  2. Run the cockroach start-single-node command:

    icon/buttons/copy
    $ cockroach start-single-node --advertise-addr 'localhost' --insecure
    

    This starts an insecure, single-node cluster.

  3. Take note of the following connection information in the SQL shell welcome text:

    CockroachDB node starting at 2021-08-30 17:25:30.06524 +0000 UTC (took 4.3s)
    build:               CCL v21.1.6 @ 2021/07/20 15:33:43 (go1.15.11)
    webui:               http://localhost:8080
    sql:                 postgresql://root@localhost:26257?sslmode=disable
    

    You'll use the sql connection string to connect to the cluster later in this tutorial.

Warning:

The --insecure flag used in this tutorial is intended for non-production testing only. To run CockroachDB in production, use a secure cluster instead.

Step 2. Get the code

Clone the code's GitHub repo:

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$ git clone https://github.com/cockroachlabs/example-app-go-gorm

The project has the following directory structure:

├── README.md
└── main.go

The main.go file defines an Account struct that maps to a new accounts table in the bank database. The file also contains some read and write database operations that are executed in the main method of the program.

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package main

import (
    "bufio"
    "context"
    "fmt"
    "log"
    "math/rand"
    "os"
    "time"

    "github.com/cockroachdb/cockroach-go/v2/crdb/crdbgorm"
    "github.com/google/uuid"
    "gorm.io/driver/postgres"
    "gorm.io/gorm"
    "gorm.io/gorm/schema"
)

// Account is our model, which corresponds to the "accounts" table
type Account struct {
    ID      uuid.UUID `gorm:"type:uuid;default:uuid_generate_v4()"`
    Balance int
}

// The `acctIDs` global variable tracks the random IDs generated by `addAccounts`
var acctIDs []uuid.UUID

// Insert new rows into the "accounts" table
// This function generates new UUIDs and random balances for each row, and
// then it appends the ID to the `acctIDs`, which other functions use to track the IDs
func addAccounts(db *gorm.DB, numRows int, transferAmount int) error {
    log.Printf("Creating %d new accounts...", numRows)
    for i := 0; i < numRows; i++ {
        newID := uuid.New()
        newBalance := rand.Intn(10000) + transferAmount
        if err := db.Create(&Account{ID: newID, Balance: newBalance}).Error; err != nil {
            return err
        }
        acctIDs = append(acctIDs, newID)
    }
    log.Println("Accounts created.")
    return nil
}

// Transfer funds between accounts
// This function adds `amount` to the "balance" column of the row with the "id" column matching `toID`,
// and removes `amount` from the "balance" column of the row with the "id" column matching `fromID`
func transferFunds(db *gorm.DB, fromID uuid.UUID, toID uuid.UUID, amount int) error {
    log.Printf("Transferring %d from account %s to account %s...", amount, fromID, toID)
    var fromAccount Account
    var toAccount Account

    db.First(&fromAccount, fromID)
    db.First(&toAccount, toID)

    if fromAccount.Balance < amount {
        return fmt.Errorf("account %s balance %d is lower than transfer amount %d", fromAccount.ID, fromAccount.Balance, amount)
    }

    fromAccount.Balance -= amount
    toAccount.Balance += amount

    if err := db.Save(&fromAccount).Error; err != nil {
        return err
    }
    if err := db.Save(&toAccount).Error; err != nil {
        return err
    }
    log.Println("Funds transferred.")
    return nil
}

// Print IDs and balances for all rows in "accounts" table
func printBalances(db *gorm.DB) {
    var accounts []Account
    db.Find(&accounts)
    fmt.Printf("Balance at '%s':\n", time.Now())
    for _, account := range accounts {
        fmt.Printf("%s %d\n", account.ID, account.Balance)
    }
}

// Delete all rows in "accounts" table inserted by `main` (i.e., tracked by `acctIDs`)
func deleteAccounts(db *gorm.DB, accountIDs []uuid.UUID) error {
    log.Println("Deleting accounts created...")
    err := db.Where("id IN ?", accountIDs).Delete(Account{}).Error
    if err != nil {
        return err
    }
    log.Println("Accounts deleted.")
    return nil
}

func main() {
    // Read in connection string
    scanner := bufio.NewScanner(os.Stdin)
    log.Println("Enter a connection string: ")
    scanner.Scan()
    connstring := os.ExpandEnv(scanner.Text())

    // Connect to the "bank" database
    db, err := gorm.Open(postgres.Open(connstring), &gorm.Config{
        NamingStrategy: schema.NamingStrategy{
            TablePrefix: "bank.",
        },
    })
    if err != nil {
        log.Fatal("error configuring the database: ", err)
    }

    // Automatically create the "accounts" table based on the `Account`
    // model.
    db.AutoMigrate(&Account{})

    // The number of initial rows to insert
    const numAccts int = 5

    // The amount to be transferred between two accounts.
    const transferAmt int = 100

    // Insert `numAccts` rows into the "accounts" table.
    // To handle potential transaction retry errors, we wrap the call
    // to `addAccounts` in `crdbgorm.ExecuteTx`, a helper function for
    // GORM which implements a retry loop
    if err := crdbgorm.ExecuteTx(context.Background(), db, nil,
        func(tx *gorm.DB) error {
            return addAccounts(db, numAccts, transferAmt)
        },
    ); err != nil {
        // For information and reference documentation, see:
        //   https://www.cockroachlabs.com/docs/stable/error-handling-and-troubleshooting.html
        fmt.Println(err)
    }

    // Print balances before transfer.
    printBalances(db)

    // Select two account IDs
    fromID := acctIDs[0]
    toID := acctIDs[0:][rand.Intn(len(acctIDs))]

    // Transfer funds between accounts.  To handle potential
    // transaction retry errors, we wrap the call to `transferFunds`
    // in `crdbgorm.ExecuteTx`
    if err := crdbgorm.ExecuteTx(context.Background(), db, nil,
        func(tx *gorm.DB) error {
            return transferFunds(tx, fromID, toID, transferAmt)
        },
    ); err != nil {
        // For information and reference documentation, see:
        //   https://www.cockroachlabs.com/docs/stable/error-handling-and-troubleshooting.html
        fmt.Println(err)
    }

    // Print balances after transfer to ensure that it worked.
    printBalances(db)

    // Delete all accounts created by the earlier call to `addAccounts`
    // To handle potential transaction retry errors, we wrap the call
    // to `deleteAccounts` in `crdbgorm.ExecuteTx`
    if err := crdbgorm.ExecuteTx(context.Background(), db, nil,
        func(tx *gorm.DB) error {
            return deleteAccounts(db, acctIDs)
        },
    ); err != nil {
        // For information and reference documentation, see:
        //   https://www.cockroachlabs.com/docs/stable/error-handling-and-troubleshooting.html
        fmt.Println(err)
    }
}

Note:

CockroachDB may require the client to retry a transaction in the case of read/write contention. The CockroachDB Go client includes a generic retry function (ExecuteTx()) that runs inside a transaction and retries it as needed. The code sample shows how you can use this function to wrap SQL statements.

Step 3. Run the code

  1. Initialize the module:

    icon/buttons/copy
    $ go mod init basic-sample && go mod tidy
    
  2. Run the code:

    icon/buttons/copy
    $ go run main.go
    

    The program will prompt you for a connection string to the database:

    Enter a connection string:
    
  3. Enter the connection string to your running cluster.

    Tip:

    postgresql://root@localhost:26257?sslmode=disable should be the sql connection URL provided in the cockroach welcome text.

    Tip:

    Use the connection string provided in the Connection info window of the CockroachDB Cloud Console.

    Note:

    You need to provide a SQL user password in order to securely connect to a CockroachDB Cloud cluster. The connection string should have a placeholder for the password (<ENTER-PASSWORD>).

    The output should look similar to the following:

    2021/09/16 14:17:12 Creating 5 new accounts...
    2021/09/16 14:17:12 Accounts created.
    Balance at '2021-09-16 14:17:12.68843 -0400 EDT m=+2.760587790':
    1580d2f4-c9ec-4f26-bbe7-6a53e9aa5170 1947
    26ddc77b-8068-409b-b305-0c5d873f7c43 7987
    3d97ea5a-5108-4388-88e8-92524d5de5e8 4159
    af49831d-d637-4a20-a9a7-01e9fe4628fe 8181
    f0cc97ef-e3fe-4abb-a44a-0dd04207f7d4 2181
    2021/09/16 14:17:12 Transferring 100 from account af49831d-d637-4a20-a9a7-01e9fe4628fe to account 3d97ea5a-5108-4388-88e8-92524d5de5e8...
    2021/09/16 14:17:12 Funds transferred.
    Balance at '2021-09-16 14:17:12.759686 -0400 EDT m=+2.831841311':
    1580d2f4-c9ec-4f26-bbe7-6a53e9aa5170 1947
    26ddc77b-8068-409b-b305-0c5d873f7c43 7987
    3d97ea5a-5108-4388-88e8-92524d5de5e8 4259
    af49831d-d637-4a20-a9a7-01e9fe4628fe 8081
    f0cc97ef-e3fe-4abb-a44a-0dd04207f7d4 2181
    2021/09/16 14:17:12 Deleting accounts created...
    2021/09/16 14:17:12 Accounts deleted.
    

    The code runs a migration that creates the accounts table in the bank database, based on the Account struct defined at the top of the main.go file.

    As shown in the output, the code also does the following:

    • Inserts some rows into the accounts table.
    • Reads values from the table.
    • Updates values in the table.
    • Deletes values from the table.

What's next?

Read more about using the GORM ORM, or check out a more realistic implementation of GORM with CockroachDB in our examples-orms repository.

You might also be interested in the following pages:

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