Example: Node.js "Hello World" Application

This code sample is a "hello world" application that runs on Node.js. The sample illustrates how to complete the following tasks:

  • Connect to a Cloud Bigtable instance.
  • Create a new table.
  • Write data to the table.
  • Read the data back.
  • Delete the table.

Running the sample

This code sample uses the Cloud Bigtable package of the Google Cloud Client Library for Node.js to communicate with Cloud Bigtable.

To run this sample program, follow the instructions for the sample on GitHub.

Using the Cloud Client Library with Cloud Bigtable

The sample application connects to Cloud Bigtable and demonstrates some simple operations.

Requiring the client library

The sample requires the @google-cloud/bigtable module, which provides the Bigtable class.

samples/hello-world/index.js 
const Bigtable = require('@google-cloud/bigtable');

Connecting to Cloud Bigtable

To connect to Cloud Bigtable, create a new Bigtable object. Then call its instance() method to get an Instance object that represents your Cloud Bigtable instance.

samples/hello-world/index.js 
const bigtableClient = new Bigtable();
const instance = bigtableClient.instance(INSTANCE_ID);

Creating a table

Call the instance's table() method to get a Table object that represents the table for "hello world" greetings. If the table doesn't exist, call the table's create() method to create a table with a single column family that retains one version of each value.

samples/hello-world/index.js 
const table = instance.table(TABLE_ID);
const [tableExists] = await table.exists();
if (!tableExists) {
  console.log(`Creating table ${TABLE_ID}`);
  const options = {
    families: [
      {
        name: COLUMN_FAMILY_ID,
        rule: {
          versions: 1,
        },
      },
    ],
  };
  await table.create(options);
}

Writing rows to a table

Use an array of greeting strings to create some new rows for the table: call the array's map() method to create a new array of objects that represent rows, then call the table's insert() method to add the rows to the table.

samples/hello-world/index.js 
console.log('Write some greetings to the table');
const greetings = ['Hello World!', 'Hello Bigtable!', 'Hello Node!'];
const rowsToInsert = greetings.map((greeting, index) => ({
  // Note: This example uses sequential numeric IDs for simplicity, but this
  // pattern can result in poor performance in a production application.
  // Rows are stored in sorted order by key, so sequential keys can result
  // in poor distribution of operations across nodes.
  //
  // For more information about how to design an effective schema for Cloud
  // Bigtable, see the documentation:
  // https://cloud.google.com/bigtable/docs/schema-design
  key: `greeting${index}`,
  data: {
    [COLUMN_FAMILY_ID]: {
      [COLUMN_QUALIFIER]: {
        // Setting the timestamp allows the client to perform retries. If
        // server-side time is used, retries may cause multiple cells to
        // be generated.
        timestamp: new Date(),
        value: greeting,
      },
    },
  },
}));
await table.insert(rowsToInsert);

Creating a filter

Before you read the data that you wrote, create a filter to limit the data that Cloud Bigtable returns. This filter tells Cloud Bigtable to return only the most recent version of each value, even if the table contains older versions that haven't been garbage-collected.

samples/hello-world/index.js 
const filter = [
  {
    column: {
      cellLimit: 1, // Only retrieve the most recent version of the cell.
    },
  },
];

Reading a row by its row key

Call the table's row() method to get a reference to the row with a specific row key. Then call the row's get() method, passing in the filter, to get one version of each value in that row.

samples/hello-world/index.js 
console.log('Reading a single row by row key');
const [singleRow] = await table.row('greeting0').get({filter});
console.log(`\tRead: ${getRowGreeting(singleRow)}`);

Scanning all table rows

Call the table's getRows() method, passing in the filter, to get all of the rows in the table. Because you passed in the filter, Cloud Bigtable returns only one version of each value.

samples/hello-world/index.js 
console.log('Reading the entire table');
// Note: For improved performance in production applications, call
// `Table#readStream` to get a stream of rows. See the API documentation:
// https://cloud.google.com/nodejs/docs/reference/bigtable/latest/Table#createReadStream
const [allRows] = await table.getRows({filter});
for (const row of allRows) {
  console.log(`\tRead: ${getRowGreeting(row)}`);
}

Deleting a table

Delete the table with the table's delete() method.

samples/hello-world/index.js 
console.log('Delete the table');
await table.delete();

Putting it all together

Here is the full code sample without comments.

samples/hello-world/index.js 



const Bigtable = require('@google-cloud/bigtable');

const TABLE_ID = 'Hello-Bigtable';
const COLUMN_FAMILY_ID = 'cf1';
const COLUMN_QUALIFIER = 'greeting';
const INSTANCE_ID = process.env.INSTANCE_ID;

if (!INSTANCE_ID) {
  throw new Error('Environment variables for INSTANCE_ID must be set!');
}

const getRowGreeting = row => {
  return row.data[COLUMN_FAMILY_ID][COLUMN_QUALIFIER][0].value;
};

(async () => {
  try {
    const bigtableClient = new Bigtable();
    const instance = bigtableClient.instance(INSTANCE_ID);

    const table = instance.table(TABLE_ID);
    const [tableExists] = await table.exists();
    if (!tableExists) {
      console.log(`Creating table ${TABLE_ID}`);
      const options = {
        families: [
          {
            name: COLUMN_FAMILY_ID,
            rule: {
              versions: 1,
            },
          },
        ],
      };
      await table.create(options);
    }

    console.log('Write some greetings to the table');
    const greetings = ['Hello World!', 'Hello Bigtable!', 'Hello Node!'];
    const rowsToInsert = greetings.map((greeting, index) => ({
      key: `greeting${index}`,
      data: {
        [COLUMN_FAMILY_ID]: {
          [COLUMN_QUALIFIER]: {
            timestamp: new Date(),
            value: greeting,
          },
        },
      },
    }));
    await table.insert(rowsToInsert);

    const filter = [
      {
        column: {
          cellLimit: 1, // Only retrieve the most recent version of the cell.
        },
      },
    ];

    console.log('Reading a single row by row key');
    const [singleRow] = await table.row('greeting0').get({filter});
    console.log(`\tRead: ${getRowGreeting(singleRow)}`);

    console.log('Reading the entire table');
    const [allRows] = await table.getRows({filter});
    for (const row of allRows) {
      console.log(`\tRead: ${getRowGreeting(row)}`);
    }

    console.log('Delete the table');
    await table.delete();
  } catch (error) {
    console.error('Something went wrong:', error);
  }
})();