Build a Simple CRUD Node.js App with CockroachDB and the node-postgres Driver

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This tutorial shows you how build a simple Node.js application with CockroachDB and the node-postgres driver.

Step 1. Start CockroachDB

Create a free cluster

Note:

Organizations without billing information on file can only create one CockroachDB Basic cluster.

If you haven't already, sign up for a CockroachDB Cloud account.
Log in to your CockroachDB Cloud account.
On the Clusters page, click Create cluster.
On the Select a plan page, select Basic.
On the Cloud & Regions page, select a cloud provider (GCP or AWS) in the Cloud provider section.
In the Regions section, select a region for the cluster. Refer to CockroachDB Cloud Regions for the regions where CockroachDB Basic clusters can be deployed. To create a multi-region cluster, click Add region and select additional regions.
Click Next: Capacity.
On the Capacity page, select Start for free. Click Next: Finalize.
On the Finalize page, click Create cluster.

Your cluster will be created in a few seconds and the Create SQL user dialog will display.

Set up your cluster connection

Navigate to the cluster's Overview page, and select Connect.
Under the Connection String tab, download the cluster certificate.
Take note of the connection string provided. You'll use it to connect to the database later in this tutorial.

If you haven't already, download the CockroachDB binary.
Run the cockroach start-single-node command:
```
$ cockroach start-single-node --advertise-addr 'localhost' --insecure
```
This starts an insecure, single-node cluster.

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:

$ git clone https://github.com/cockroachlabs/example-app-node-postgres

The project has the following directory structure:

├── README.md
├── app.js
├── dbinit.sql
└── package.json

The dbinit.sql file initializes the database schema that the application uses:

CREATE TABLE accounts (
    id UUID PRIMARY KEY,
    balance INT8
);

The app.js file contains the code for INSERT, SELECT, UPDATE, and DELETE SQL operations:

const { Pool } = require("pg");
const { v4: uuidv4 } = require("uuid");

var accountValues = Array(3);

// Wrapper for a transaction.  This automatically re-calls the operation with
// the client as an argument as long as the database server asks for
// the transaction to be retried.
async function retryTxn(n, max, client, operation, callback) {
  const backoffInterval = 100; // millis
  const maxTries = 5;
  let tries = 0;

  while (true) {
    await client.query('BEGIN;');

    tries++;

    try {
      const result = await operation(client, callback);
      await client.query('COMMIT;');
      return result;
    } catch (err) {
      await client.query('ROLLBACK;');

      if (err.code !== '40001' || tries == maxTries) {
        throw err;
      } else {
        console.log('Transaction failed. Retrying.');
        console.log(err.message);
        await new Promise(r => setTimeout(r, tries * backoffInterval));
      }
    }
  }
}

// This function is called within the first transaction. It inserts some initial values into the "accounts" table.
async function initTable(client, callback) {
  let i = 0;
  while (i < accountValues.length) {
    accountValues[i] = await uuidv4();
    i++;
  }

  const insertStatement =
    "INSERT INTO accounts (id, balance) VALUES ($1, 1000), ($2, 250), ($3, 0);";
  await client.query(insertStatement, accountValues, callback);

  const selectBalanceStatement = "SELECT id, balance FROM accounts;";
  await client.query(selectBalanceStatement, callback);
}

// This function updates the values of two rows, simulating a "transfer" of funds.
async function transferFunds(client, callback) {
  const from = accountValues[0];
  const to = accountValues[1];
  const amount = 100;
  const selectFromBalanceStatement =
    "SELECT balance FROM accounts WHERE id = $1;";
  const selectFromValues = [from];
  await client.query(
    selectFromBalanceStatement,
    selectFromValues,
    (err, res) => {
      if (err) {
        return callback(err);
      } else if (res.rows.length === 0) {
        console.log("account not found in table");
        return callback(err);
      }
      var acctBal = res.rows[0].balance;
      if (acctBal < amount) {
        return callback(new Error("insufficient funds"));
      }
    }
  );

  const updateFromBalanceStatement =
    "UPDATE accounts SET balance = balance - $1 WHERE id = $2;";
  const updateFromValues = [amount, from];
  await client.query(updateFromBalanceStatement, updateFromValues, callback);

  const updateToBalanceStatement =
    "UPDATE accounts SET balance = balance + $1 WHERE id = $2;";
  const updateToValues = [amount, to];
  await client.query(updateToBalanceStatement, updateToValues, callback);

  const selectBalanceStatement = "SELECT id, balance FROM accounts;";
  await client.query(selectBalanceStatement, callback);
}

// This function deletes the third row in the accounts table.
async function deleteAccounts(client, callback) {
  const deleteStatement = "DELETE FROM accounts WHERE id = $1;";
  await client.query(deleteStatement, [accountValues[2]], callback);

  const selectBalanceStatement = "SELECT id, balance FROM accounts;";
  await client.query(selectBalanceStatement, callback);
}

// Run the transactions in the connection pool
(async () => {
  const connectionString = process.env.DATABASE_URL;
  const pool = new Pool({
    connectionString,
    application_name: "$ docs_simplecrud_node-postgres",
  });

  // Connect to database
  const client = await pool.connect();

  // Callback
  function cb(err, res) {
    if (err) throw err;

    if (res.rows.length > 0) {
      console.log("New account balances:");
      res.rows.forEach((row) => {
        console.log(row);
      });
    }
  }

  // Initialize table in transaction retry wrapper
  console.log("Initializing accounts table...");
  await retryTxn(0, 15, client, initTable, cb);

  // Transfer funds in transaction retry wrapper
  console.log("Transferring funds...");
  await retryTxn(0, 15, client, transferFunds, cb);

  // Delete a row in transaction retry wrapper
  console.log("Deleting a row...");
  await retryTxn(0, 15, client, deleteAccounts, cb);

  // Exit program
  process.exit();
})().catch((err) => console.log(err.stack));

All of the database operations are wrapped in a helper function named retryTxn. This function attempts to commit statements in the context of an explicit transaction. If a retry error is thrown, the wrapper will retry committing the transaction, with exponential backoff, until the maximum number of retries is reached (by default, 15).

Step 3. Initialize the database

To initialize the example database, use the cockroach sql command to execute the SQL statements in the dbinit.sql file:

cat dbinit.sql | cockroach sql --url "<connection-string>"

Where <connection-string> is the connection string you obtained earlier from the CockroachDB Cloud Console.

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Build a Simple CRUD Node.js App with CockroachDB and the node-postgres Driver

Step 1. Start CockroachDB

Create a free cluster

Set up your cluster connection

Step 2. Get the code

Step 3. Initialize the database

Step 4. Run the code

What's next?