This tutorial shows you how build a simple Node.js application with CockroachDB using a PostgreSQL-compatible driver or ORM. We've tested and can recommend the Node.js pg driver and the Sequelize ORM, so those are featured here.
Before You Begin
Make sure you have already installed CockroachDB.
Step 1. Install Node.js packages
To let your application communicate with CockroachDB, install the Node.js pg driver:
$ npm install pg
The example app on this page also requires async:
$ npm install async
Step 2. Start a single-node cluster
For the purpose of this tutorial, you need only one CockroachDB node running in insecure mode:
$ cockroach start \
--insecure \
--store=hello-1 \
--host=localhost
Step 3. Create a user
In a new terminal, as the root user, use the cockroach user command to create a new user, maxroach.
$ cockroach user set maxroach --insecure
Step 4. Create a database and grant privileges
As the root user, use the built-in SQL client to create a bank database.
$ cockroach sql --insecure -e 'CREATE DATABASE bank'
Then grant privileges to the maxroach user.
$ cockroach sql --insecure -e 'GRANT ALL ON DATABASE bank TO maxroach'
Step 5. Run the Node.js code
Now that you have a database and a user, you'll run code to create a table and insert some rows, and then you'll run code to read and update values as an atomic transaction.
Basic Statements
First, use the following code to connect as the maxroach user and execute some basic SQL statements, creating a table, inserting rows, and reading and printing the rows.
Download the basic-sample.js file, or create the file yourself and copy the code into it.
var async = require('async');
// Require the driver.
var pg = require('pg');
// Connect to the "bank" database.
var config = {
user: 'maxroach',
host: 'localhost',
database: 'bank',
port: 26257
};
// Create a pool.
var pool = new pg.Pool(config);
pool.connect(function (err, client, done) {
// Closes communication with the database and exits.
var finish = function () {
done();
process.exit();
};
if (err) {
console.error('could not connect to cockroachdb', err);
finish();
}
async.waterfall([
function (next) {
// Create the "accounts" table.
client.query('CREATE TABLE IF NOT EXISTS accounts (id INT PRIMARY KEY, balance INT);', next);
},
function (results, next) {
// Insert two rows into the "accounts" table.
client.query('INSERT INTO accounts (id, balance) VALUES (1, 1000), (2, 250);', next);
},
function (results, next) {
// Print out the balances.
client.query('SELECT id, balance FROM accounts;', next);
},
],
function (err, results) {
if (err) {
console.error('error inserting into and selecting from accounts', err);
finish();
}
console.log('Initial balances:');
results.rows.forEach(function (row) {
console.log(row);
});
finish();
});
});
Then run the code:
$ node basic-sample.js
The output should be:
Initial balances:
{ id: '1', balance: '1000' }
{ id: '2', balance: '250' }
Transaction (with retry logic)
Next, use the following code to again connect as the maxroach user but this time execute a batch of statements as an atomic transaction to transfer funds from one account to another and then read the updated values, where all included statements are either committed or aborted.
Download the txn-sample.js file, or create the file yourself and copy the code into it.
SERIALIZABLE isolation level, CockroachDB may require the client to retry a transaction in case of read/write contention. CockroachDB provides a generic retry function that runs inside a transaction and retries it as needed. You can copy and paste the retry function from here into your code.var async = require('async');
// Require the driver.
var pg = require('pg');
// Connect to the cluster.
var config = {
user: 'maxroach',
host: 'localhost',
database: 'bank',
port: 26257
};
// Wrapper for a transaction.
// This automatically re-calls "op" with the client as an argument as
// long as the database server asks for the transaction to be retried.
function txnWrapper(client, op, next) {
client.query('BEGIN; SAVEPOINT cockroach_restart', function (err) {
if (err) {
return next(err);
}
var released = false;
async.doWhilst(function (done) {
var handleError = function (err) {
// If we got an error, see if it's a retryable one and, if so, restart.
if (err.code === '40001') {
// Signal the database that we'll retry.
return client.query('ROLLBACK TO SAVEPOINT cockroach_restart', done);
}
// A non-retryable error; break out of the doWhilst with an error.
return done(err);
};
// Attempt the work.
op(client, function (err) {
if (err) {
return handleError(err);
}
var opResults = arguments;
// If we reach this point, release and commit.
client.query('RELEASE SAVEPOINT cockroach_restart', function (err) {
if (err) {
return handleError(err);
}
released = true;
return done.apply(null, opResults);
});
});
},
function () {
return !released;
},
function (err) {
if (err) {
client.query('ROLLBACK', function () {
next(err);
});
} else {
var txnResults = arguments;
client.query('COMMIT', function(err) {
if (err) {
return next(err);
} else {
return next.apply(null, txnResults);
}
});
}
});
});
}
// The transaction we want to run.
function transferFunds(client, from, to, amount, next) {
// Check the current balance.
client.query('SELECT balance FROM accounts WHERE id = $1', [from], function (err, results) {
if (err) {
return next(err);
} else if (results.rows.length === 0) {
return next(new Error('account not found in table'));
}
var acctBal = results.rows[0].balance;
if (acctBal >= amount) {
// Perform the transfer.
async.waterfall([
function (next) {
// Subtract amount from account 1.
client.query('UPDATE accounts SET balance = balance - $1 WHERE id = $2', [amount, from], next);
},
function (updateResult, next) {
// Add amount to account 2.
client.query('UPDATE accounts SET balance = balance + $1 WHERE id = $2', [amount, to], next);
}, function (updateResult, next) {
// Fetch account balances after updates.
client.query('SELECT id, balance FROM accounts', function (err, selectResult) {
next(err, selectResult ? selectResult.rows : null);
});
}
], next);
} else {
next(new Error('insufficient funds'));
}
});
}
// Create a pool.
var pool = new pg.Pool(config);
pool.connect(function (err, client, done) {
// Closes communication with the database and exits.
var finish = function () {
done();
process.exit();
};
if (err) {
console.error('could not connect to cockroachdb', err);
finish();
}
// Execute the transaction.
txnWrapper(client,
function (client, next) {
transferFunds(client, 1, 2, 100, next);
},
function (err, results) {
if (err) {
console.error('error performing transaction', err);
finish();
}
console.log('Balances after transfer:');
results.forEach(function (result) {
console.log(result);
});
finish();
});
});
Then run the code:
$ node txn-sample.js
The output should be:
Balances after transfer:
{ id: '1', balance: '900' }
{ id: '2', balance: '350' }
However, if you want to verify that funds were transferred from one account to another, use the built-in SQL client:
$ cockroach sql --insecure -e 'SELECT id, balance FROM accounts' --database=bank
+----+---------+
| id | balance |
+----+---------+
| 1 | 900 |
| 2 | 350 |
+----+---------+
(2 rows)
What's Next?
Read more about using the Node.js pg driver.
You might also be interested in using a local cluster to explore the following core CockroachDB features:
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